World of Ham Radio 1994 January/AMSOFT_1994.iso/misc/aprs/amsoft.iii

Text File | 1993-12-31 | 133.0 KB | 2,172 lines

                  AUTOMATIC PACKET REPORTING SYSTEM (APRS)

APRS is the result of my experience over the last 13 years with trying
to use packet radio for real-time communications or public service events.
Packet radio has great potential but so far has been best used for passing
large volumes of message traffic from point to point or into the national
distribution system.  It has been difficult to apply packet to real time
events where information has a very short life time.  Typically, several
steps are involved in preparing and passing message traffic including
decisions about routing and connectivity.

APRS avoids the complexity and limitations of trying to maintain a
connected network.  It permits any number of stations to participate and
exchanges data just like voice users would on a single voice net.  Any
station that has information to contribute simply transmits it, and all
stations receive it and log it.  Secondly, APRS recognizes that one of the
greatest real-time needs at any special event or emergency is the tracking of
key assets.  Where is the Event Leader?  Where are the emergency vehicles?
Where is the head of the parade?  Where are the VIP's?  Where is the mobile
ATV camera?  Where are the mobiles?  Included on the distribution disk are
several README text files on specific applications of APRS such as for
weather nets, direction finding, plotting satellite contacts, and so forth.

APRS accomplishes the real-time display of operational traffic via
UI frame broadcasts and map displays.  There are three major display
subsystems and a number of other minor displays as follows:

     LATEST BEACONS - This display maintains a list of the latest UI frame
received from each station.  In effect, this is a multi-station one-line
broadcast message system.  Since the lines contain the LATEST time of receipt,
this display shows if a station is still on line within the last few minutes.

     POSITIONS - This display maintains a separate list of the positions of
each station.  Each position report can also contain a brief comment.  These
lines retain the time of FIRST receiving a given position report and give an
indication of the latency in the network over unreliable paths such as HF.

     MAPS - Maps to any scale from .5 miles up to 2000 miles can be
displayed. Stations are instantly displayed when they transmit a properly
formatted position beacon.  Stations with a reported course and speed can be
dead-reckoned to their present position.  You can center the map anywhere.

     MESSAGES -  In addition to the BEACON text which is used to broadcast
information to all other stations on the net, there is an operator-to-operator
message capability.  Any station can send a one line message to any other
station.  On receipt, the messages are acknowledged and displayed on the
bottom of the receiving stations screen until the operator hits the K key to
kill them.  These messages are ideal for station-to-station comms while
remaining within the APRS environment.  However, they are not as effecient as
the connected protocol, and should not be used reutinely for Rag-Chewing on
a busy APRS net.

     ALL TRAFFIC LOG - This display is a time sequenced log of every new
beacon or one line message sent.  Beacons are logged the first time they are
received.  This is in contrast to the LATEST display which shows the most
recent time of receipt of a beacon text.

     WHEN-HEARD - This display maintains a count of the total number of
transmissions from each station per hour.  These statistics are ideal for
displaying the connectivity of the network over varying paths, such as HF, or
to see when stations enter and leave the net.

STATION TRACKING.  Although APRS automatically tracks mobile packet stations
interfaced to GPS or LORAN navigation, the graphic capability of the maps works
perfectly well with manual tracking or with GridSquares.  Any station on HF or
VHF that includes his GridSquare in brackets as the first text in his beacon
text will be plotted by APRS.  Additionally, any station can place an
object on his map including himself and within seconds that object appears on
all other station displays. In the example of a parade, as each checkpoint with
packet comes on line, its position is instantly displayed to all in the net.
Whenever a station moves, he just updates his position on his map and that
movement is transmitted to all other stations.  To track other event assets,
only one packet operator needs to monitor voice traffic to hear where things
are.  As he maintains the positions and movements of all assets on his screen,
all other displays running APRS software display the same displays.

GRID SQUARES:  As of version 2.05, APRS now also plots stations by gridsquares.
Since four-digit grid squares only locate a station to the nearest 60 miles
or so, and six-digit gridsquares only specify stations to the nearest 3 miles
or so, APRS will not display stations reported via gridsquares on map ranges
less than 128 and 8 miles respectively.  Stations reported by grid squares
will each be assigned an exact LAT/LON which is offset from the center of the
grid acording to an algorithm based on the letters of their callsigns.  This
prevents all stations in the same grid square from all being displayed on one
spot in the center and spreads them out in the grid.  The resulting POSIT in
the POSITION list is annotated to indicate that the position is approximate.
Another advantage of GridSquare reporting in APRS is that it allows cautious
people to participate in APRS without revealing their exact location.

USING DUMB TERMINALS IN AN APRS NETWORK:  The simplicity and usefulness
of this geographic capability cannot be over stressed.  Stations running APRS
simply move the cursor to where they think they are on the screen and their
LAT/LONG coordinates are automatically transmitted to all other stations.
Even the simplest of portable packet stations with dumb terminals can report
their positions if a pre-printed map is made available to all net
participants which has a LAT/LONG grid reference.  The portable station just
looks at the map and enters his LAT/LONG into his beacon text.  Using the
same map, he can plot with pins the location of all other stations as he sees
their position reports go by.  Beginning with version 2.05, APRS also plots
station positions based on Grid Squares.  Eventually, we hope that all stations,
no matter how they are using their TNC, will include their LAT/LONG or Grid
Square in their Beacon Text so that their location is immediately available.
See the file README.DUM for details on APRS formats and help in using dumb
terminals in an APRS network.

SPACE APPLICATIONS:  APRS could be a solution to the effective use of orbiting
terrestrial style packet radio digipeaters in space such as on the Shuttle, MIR,
AO-21 and ARSENE.  The problem with space digipeaters is the saturation on the
uplink channel which makes the use of a normal CONNECTED protocol impractical.
For a CONNECTED contact, a total of five successive and successful packet
transmissions are required.  Not only does APRS reduce this to one packet, but
it also capitalizes on the most fascinating aspect of the amateur radio hobby,
and that is the display on a map of the location of those stations.  If all
stations were encouraged to simply insert their LAT/LONG or Grid Square as the
first characters of their beacon text, everyone within the satellite footprint
would see the location of every successful uplink.  Since the shuttle is a
rapidly moving object, the locations of successful uplink stations will move
progressively along the ground track.  All it would take to implement this
capability is a single AMSAT news bulletin to ask all stations to insert their
POSITS in their beacon text.  No changes onboard the shuttle or MIR would be
required.  See README.SAT for further details.

FOX HUNTING OR DIRECTION FINDING:  APRS is an excellent tool for
triangulating the location of a hidden transmitter, balloon, or interfering
signal.  The X command (cross fiX)has been added to permit displaying the
intersection of bearing lines from a number of reporting stations.  To use
APRS in this manner, each station having a bearing report on the direction of
the target, simply enters that bearing in the COURSE field for his own
station.  His station is now not only reporting his station location, but
also a line of bearing.  All stations running APRS can simply hit the X key
to display the intersection of these bearing lines.  Further, if a DF vehicle
has a GPS or LORAN-C device on board, he can be tracked and directed right to
the location of the target.

PROTOCOL - Since the objective of APRS is the rapid dissemmination of real-time
information using packet UI frames, a fundamental precept is that old
information is less important than new information.  All beacons, position
reports, messages and display graphics are redundantly transmitted but at a
longer and longer repition rate.  Each new beacon is transmitted immediately,
then 20 seconds later.  After every transmission, the period is doubled.  After
ten minutes only six packets have been transmitted.  After an hour this results
in only 3 more beacons; and only 3 more for the rest of the day!  All trans-
missions cease if the CTRL-X command is used.  But a transmission can be forced
at any time by hitting the T key.

COMMANDS:   In most cases the keyboard is always active.  There is a mneumonic
relationship between all functions and the appropriate key.  For this reason,
the PC function keys are avoided.  The most useful commands are as follows:

  Space Key           - Display map and all station locations
  H - Help            - Two alternating pages of help
  L - Latest beacons  - Displays the latest BText from each station
  P - Positions       - Displays a list of all stations reporting positions
  C - Controls        - Display a one line status of all control states
  W - When heard      - Displays the number of beacons per hour per station
  S - Send            - Send a directed message to a station
  Alt-F   Features    - Cities, Leaders, Tags, Roads or waterways on/off
  Ctrl-L  Load file   - Loads a previously saved file and screen location
  Ctrl-S  Save file   - Saves all positions and Beacons for later restart
  alt-R   Replay      - Replay the recent movements of stations in memory
                        or replay a track history file
  Ctrl-V  Via digi    - Used to change your VIA path for outgoing packets

DEMONSTRATION FILE:  To see how the APRS system works on an ordinary packet
traffic frequency, use ctrl-L to load the file called FREQ505.BK.  This file
contains all the local stations on 145.05 MHz in our area.  To see the tracking
of the GPS equiped Army/Navy game football run, load the file named FBALL.BK
and replay the file named FBALL.HST and select to see only FBALL, or CHASE1.
To see the marathon event we just completed, load MARTHON.BK and replay the
MARTHON.HST file.  See Details in README.1st.

HOOKING STATIONS:  The yellow circular cursor can be moved to select any
station in the system using the arrow keys.  On the MAP display move the
cursor near any station symbol.  Then hit the RETURN key to "hook" the
station.  Detail information on that station will be displayed in the upper
left hand corner.  Alternatively, use the gray + and - keys to step through
each station one by one.  Once hooked, several functions may be performed:

     1.  LIST BEACONS - hitting the L key will list all beacons from that
     station currently in memory.

     2.  POSITION CORRECTION - performed by moving the cursor to the
     desired new location and pressing the Insert key.  You are then
     prompted to enter in a new course, speed, comments or time as needed.

     3.  DELETE - performed by hitting the Del key.  Removes the station
     from the position file.

The hook function also works on the LATEST and POSITION display lists by
using the up/down arrow keys.  If a position exists, you are given the
opportunity to display the map screen with that station centered on the
display.  This is useful for finding a station which is far off the currently
displayed map range.  If a position does not exist, you are given the
opportunity to create one.

REPLAY:  Since all beacons and position reports are retained, the ctrl-R
key may be used to replay the positions of a moving station.  The replay
is performed either from active memory, or from historical files.  HISTORY
files are automatically saved after the memory is full.  Use the C command to
initially center the map and to re-center it if the mobile station moves off
the screen.  During replay, use these single key commands:

      C - CALLsigns on/off
      R - Re-center map to presently displayed station
      F - Faster.  Speeds up playback
      W - Warp speed.  Skips every other point for still faster playback
      P - Pause
      S - Slow.  Slows down playback
      Q - Quit playback.
      PgUp/PgDn - Zoom in and out


FILES:  There are several files used by the system:

  MAPLIST .map - Contains a list of all map files to be used and also the
                 default LAT/LONG, Range and GMT offset for your location
  USA     .map - large scale map of the USA
  xxxxxxxx.map - Maps of any area to any scale.  At this writing there is
                 a whole USA map and more than 40 others.
  TKxxxxxx.HST - Track history.  The day and time that the file was saved
                 is indicated by the x's. If the file contains an interesting
                 trip or station movement for later replay, the file should
                 be renamed using DOS to a more descriptive *.HST file
  BACKUP  .BK  - Automatic backup of system every time program is quit.  This
                 file is overwritten every time the program is quit.
  BKxxxxxx.BK  - Backup file of the latest beacons and POSITS heard created
                 whenever Ctrl-S save is commanded.  Usually used to save a
                 file backup of a special event or situation.
  BLxxxxxx.LOG - Log of all new beacons received in chronological order of
                 first receipt.  A good log of text used during an event.


CHESSBOARD:  To demonstrate the flexibility of APRS in reporting the movement
of objects on screens in a net, I have drawn a chessboard map in the center
of the Gulf of Mexico.  Any two stations can play chess easily using APRS by
placing pieces on the map using the alt-A key and updating their positions
using the cursor and INSert keys!  As a start, I have already loaded all the
pieces and saved them in CHESS.BK.  To move a piece, first enable it for
uplinking using the X key on the P screen.  Then move the cursor and hit the
INSert key.  After a while each station will be transmitting the location of
every piece that it has ever moved.  So once the other station sees you move,
it is a good idea to Stop the uplinking of that piece using the S key on the
P-list to minimize channel traffic.  Monitoring stations that have also loaded
the CHESS.BK file will see the game progress too!  You should consider going
to an unused frequency so as not to clutter an active APRS net.

            AUTOMATIC PACKET REPORTING SYSTEM DIGIPEATERS

     Although digipeaters work poorly for AX.25 level 2 connections, they are
ideal for APRS operation using UI frames only.  In the Washington DC area and
Chesapeake Bay area, we are establishing a network of wide area DIGI's on the
simplex packet frequency of 145.79.  This frequency is for Keyboard QSO's and
all UI frame applications.  Operation of BBS's, forwarding, file transfers,
TCP-IP and DX clusters are discouraged.

    All wide area digipeaters have the same alias of WIDE in addition to
their normal HAM callsign.  These wide area Digi's are spaced several tens of
miles apart so that they are not too close, but that they can hit their
adjacent other WIDE digi's.  Similarly all APRS stations are initialized to
have an alias of RELAY and to send all UI frames via the path of RELAY.  THis
way, a mobile, or new station on the air does not have to know anything about
the network in advance, but to simply turn on his computer to be seen by
adjacent nodes.  After 10 minutes and his map begins to show the location of
all stations and digipeaters on frequency, he can customize his outgoing
Unproto path to specific digipeaters to cover his intended area.

     Assuming WIDE are digipeaters are about 30 to 50 miles apart it is very
easy to select an UNPROTO path prior to a road trip which will assure that
your location packets will always get back to your home area.  In the
following examples the HAM calls of EAST and WEST are used for clarity.


        WEST-3    WEST-2    WEST-1    HOME    EAST-1   EAST-2   EAST-3
         WIDE      WIDE      WIDE    RELAY     WIDE     WIDE     WIDE


    If the mobile is going east for the day, and will be operating in the
vicinity of EAST-3 digipeater, the operator can preset his UNPROTO path to be
via WIDE,EAST-2,WIDE.  Notice that not only will his packets make it back to
home from the area of EAST-3, but also from the area of EAST-1 since EAST-1
will also respond to the first WIDE in the list.  Similarly, stations in the
vicinity of EAST-3 are alerted to his movements as he leaves home, since the
WIDE,EAST-2,WIDE specification is symetrical.  If he set the UNPROTO path to
EAST-3,EAST-2,EAST-1 in the usual manner, he would not be tracked at his home
until he actually arrived at his destination.  As you can see, having the
flexibility to alternate the generic alias's of RELAY or WIDE with other
known sites gives a good degree of flexibility without having to change the
UNPROTO path while on the road.  Using the three digipeater string, he can
wander up to 150 miles in his planned direction and still be tracked by the
XYL.  If he has no idea where he is going, he can always use the path of
WIDE,WIDE or even WIDE,WIDE,WIDE and go anywhere, but with greater QRM on the
channel.  Yes there are multiple collisions, and repeats, but the packet does
get out to the third tier!

   The ultimate APRS digipeater configuration is to have modified TNC-2
digipeater code so that any digipeater hearing a packet with its callsign
anywhere in the UNPROTO path will digipeate the packet as long as it was not
previously digipeated by any stations earlier in the list.  This way, to
always report your movements back home, you always place digipeaters in your
UNPROTO command in the reverse order of your travels.  Your packets will be
digipeated back to your home area as you enter each new digipeater in your
direction of travel.  For example:


     HOME  DIGI-1    DIGI-2    DIGI-3    etc

     If we can get TAPR to modify the code, the mobile could specify the
UNPROTO path of VIA DIGI-3,DIGI-2,DIGI-1 in order to be tracked anywhere all
the way out to the area of DIGI-3.  If the mobile is in the DIGI-1/DIGI-2
area, DIGI-1 will repeat the packet.  DIGI-2 will not digi the DIGI-1 packet
because it is to the right in the list.  If DIGI-2 also hears the mobile
packet, it will pause and if it does not hear the DIGI-1 repeat, then it
will.  When DIGI-1 hears the DIGI-2 packet, it will further digipeate it,
since DIGI-2 is to its left in the field.  Similarly as the mobile enters the
2/3 area, DIGI-2 will digipeate back in the direction of DIGI-1 and DIGI-3
will pause and not transmit.  If DIGI-3 does not hear DIGI-2, then it will
digi the packet and it will go back via 2 to 1 as desired.

     This algorithm works perfectly well in reverse.  If a mobile desires to
announce his progress forward in the direction of his travel he can specify
the digipeaters in the forward direction.  Then using this algorithm, all of
his packets will be repeated in the forward direction, but not in the
backward direction.

     Until we get new UI forwarding algorithms in standard TNC's, however,
the general aliases of WIDE and RELAY will do nicely.  If fixed, known
digipeaters are available, even with the generic alias of WIDE, it is best
for fixed APRS stations to use the digipeaters unique callsign instead of
alias to avoid any ambiguity.

SEE README.HF for setting up your UNPROTO path for HF and HF/VHF gateways..

                    USING APRS FOR SPACE COMMUNICATIONS

     The Automatic Packet Reporting System could be a solution to the effective
use of orbiting terrestrial style packet radio digipeaters in the amateur
satellite program.  To date there have been three standard AX.25 1200 baud FM
transponders flown in space.  The first was on the Space Shuttle STS-35, the
second was on the space station MIR, and the third has been via the FM
transponder mode of AO-21.   The problem with a space based digipeater is the
total saturation on the uplink channel which makes the use of a normal
CONNECTED protocol impractical.  For the SAREX robot QSO mode, a total of five
successive and successful packet transmissions were required to constitute a
successful contact.  Of an estimated thousands of uplink stations, only about
250 were successful.  Recognizing the stringent requirements for success using
the CONNECTED protocol, provision was also made to recognize those stations
which were successful in getting only one packet heard onboard the shuttle.
Over 700 stations successfully completed single uplink packets.

     APRS takes advantage of this unconnected, one packet, mode to demonstrate
successful uplinks to the shuttle.  In addition, however, it capitalizes on the
most fascinating aspect of the amateur radio hobby, and that is the display on
a map of the location of those stations.  Historically, almost every aspect of
HAM radio communications has as its root, the interest in the location of other
stations.  Look at DX maps, countries worked, counties worked, grid squares,
mobile chatter; everyone is quite interested in where other stations are.

     If, instead of every station attempting to CONNECT with the Space Shuttle,
all stations were encouraged to simply insert his/her position as the first few
characters of his beacon text, everyone within the satellite footprint would
not only see when he made a successful uplink, but also where he was.  Since
the shuttle is a rapidly moving object, the locations of successful uplink
stations will move progressively along the ground track.  The weakest
successful stations will almost certainly be immediately below the spacecraft.
Stronger and more viable groundstations can show up further to the side of the
ground track.  If there is a skew in the spacecraft antenna pattern, the
pattern of successful uplink stations on the map will clearly make that
evident.  APRS responds to both LAT/LONG and GridSquare formats.  The exact
format of an APRS position report is as follows:

   Beacon Text:     !DDMM.HHN/DDDMM.HHW/CQ comments etc.....
   For example:     !3959.11N/07629.12W/Naval Academy Radio Club

   Grid Square:     [FM18xf] Naval Academy Radio Club...

     To implement this experiment on the next shuttle mission, it would only
take a single AMSAT news bulletin to ask all stations to insert their POSIT
in their beacon text.  No changes onboard the shuttle or MIR would be required.

Those stations that had APRS could then watch the successful uplink stations
plotted in real time.  Even without real time APRS, a replay of a captured text
file containing all the successful uplink packets would still give an excellent
map display after the fact.  Analysis of antenna pointing anomolies on every
orbit could be accomplished with ease.  On future missions, the UI beacon frame
might completely replace the current CONNECTED robot mode.  Without all of the
connect requests, acks, and retries at least a five fold increase in the number
of successful uplinks would be realized, and the data exchanged would be more
meaningful by a similar factor.

     To demonstrate the expected results of this experiment, I have created a
track history file that can be replayed using the Ctrl-R command.  Simply
replay the SHUTTLE.HST file and watch the contacts appear as the shuttle moves
across the country.  You may enhance the demonstration by selecting to see only
the Shuttle, STS-99, or by turning off TAGS using the Alt-T command to reduce
the clutter of callsigns on the display.  The replay can be speeded up or
slowed down by hitting the F or S keys.  Obviously, in this SHUTTLE.hst file, I
assumed that the Shuttle had its TNC connected to a GPS navigation receiver so
that it was also beaconing its position once per minute in the APRS format.

     This capability also demonstrates the practicality of using a space based
AX.25 digipeater for routine position and status reporting.  Imagine a
constellation of three AX.25 digipeater satellites all on one FM channel.  It
would not matter what satellite was in view, or when.  Mobile and portable
stations could beacon their position once every 5 minutes and be tracked
nationwide!  Just using 1200 baud AFSK, up to 1000 stations could probably be
supported just in the US and have a reasonable chance of getting a position
report through at least once every 3 hours!  Going to 9600 baud FSK would
support almost 8000 users.

                        QUICK DEMOS OF APRS

So you wanna know what this program does without reading all the README.files..
The following steps give the maximum exposure with the minimum of reading.

MARATHON EVENT:  First, run APRS and use CTRL-L to load the MARTHON.BK file.
Hit SPACE to show the position of APRS packet stations at our marathon event.
Next do a REPLAY using alt-R.  Select the File MARTHON.HST.  You will see
the LEADER and TAIL bicycles which were GPS equipped.

FOOTBALL RUN:  To see the Army/Navy game football run from Annapolis to Philly,
load FBALL.BK, and then REPLAY the FBALL.hst file.  During replay, you can
Re-center the screen with the R key and zoom in and out as needed.  To speed
up replay, hit (F)ast or (W)arp.  The CHASE1 vehicle is also in the same file.

SPACE AX.25 DIGI's:  See README.SAT for info on using APRS for plotting
satellite DX contacts and how to replay the SHUTTLE.HST demonstration.

CHANNEL MONITORNG:  Zero memory with the alt-Z.  Tune your radio to an active
packet channel and monitor for 10 minutes.  Select the LATEST display, and you
will see all UI frames (BEACONS) on the channel.  If you know where these
stations are, insert them onto the map and save the file.  Rename the file to
include the frequency for later recall.  If no one is beaconing, and you get
impatient, you can turn off the beacon-Only filter by hitting the ctrl-O
command.  Then ALL packets will be collected (but not NETROM stuff).

LOCAL AREA:  To see our local APRS net, load the FREQ579.BK file.  Zoom in to
my location and see my neighborhood streets.  I drew that map using 1200 pixels
per degree.  To see if your area is covered by an existing detail map, PgUp to
the USA map and hit the alt-M key.  The outlines of all existing maps will be
shown.  Move cursor to your area and zoom in (PgDwn) to within one of these
maps.  To move long distances, CTRL-PgUp to large scale map, move to your area
and then Ctrl-PgDn.  Have a friend place his LAT/LONG in his TNC BText as
follows:    BText !DDMM.xxN/DDDmm.xxW/Comments...  You will see him appear on
your map!  He can also just use his Grid Square enclosed in Brackets [GRidsq]
at the start of his BText.  Better yet, give him a copy of APRS and Add objects
locations to your screens by moving the cursor and using the alt-A command.
Similarly you may broadcast text back and forth by altering your BText using
the alt-B command or Send individual messages using S.  Registered (validated)
users can save a CONFIG file so that the program starts up on their preferred
map each time.  If you are Un-registered, you can save a backup file of your
screen and reload this backup file each time you start up to restore your
screen and location.  Better yet, register your copy of APRS and get a
validation number so you can save a config file.

OTHER IDEAS AND APPLICATIONS:  See README.WX for using APRS in a weather
reporting net (Ver 2.07 can include an optional home weather station serial
input to make your station automatically include WX conditions in your position
report).  See README.DF for triangulation in fox hunting, and README.SAT
for displaying satellite beacons.  Or README.HF and come join us on the APRS
HF Boater and RV tracking net.  Finally, read the full system documentation
in README.APR, and start drawing local maps as described in README.MAP.  There
is a chess board map in the middle of the Gulf of Mexico at 25N 90W (below 64
mile scale) to show the flexibility of APRS to use any maps for any purpose.
Play chess on the air using APRS!

NOW WHAT?!   APRS is a human communications tool.  Try APRS during weekly
emergency exercises or events when humans are at their stations.  Find a two
meter freq that is not saturated with BBS's and start an APRS network.  In the
Wash/Balto area we are using 145.79.  Please consider using this freq in your
area to help us build a nationwide mobile tracking network.  Encourage periodic
reporting weather nodes (not the store-and-dump kind) and keyboard QSO's to
also join your frequency.  Anyone with low duty cycle data is welcome, but
BBS's, file forwarding, TheNET and databases should operate elsewhere!  This
is NOT meant to be discriminatory, it just optimizes the frequency for the
maximum number of individual real-time users.  This is best for all HAMS if
there is a frequency where human operators can communicate in real-time and not
only exchange text, but also see the instantaneous network topology.

                      USING APRS IN THE SKYWARN SYSTEM

     The Automatic Packet Reporting System (APRS) is an ideal tool for
reporting weather conditions via packet.  The system is compatible with both
human entry as well as automatic weather station entry of weather conditions.
As of version 2.07 there is an optional ($9) automatic serial interface in
APRS to connect to the data output of the ULTIMETER-II home weather station.
With this connection, your wind conditions, temperature and optionally rain
information are all automatically inserted into your position/weather report
packet. In the APRS system, current conditions at any station are broadcast
to all stations on the net in a periodic fashion.  Not only are these
individual conditions available to all stations on the net, but also
importantly, the location of these conditions are also displayed.  There are
several capabilities of APRS that are directly applicable to the SKYWARN:

 MAP DISPLAY - Shows the location of all reporting stations, their wind
     speed and direction.  Can also show the location of other objects, such
     as reports of TStorms, Hail, Tornados, etc

 WEATHER ONLY - Using the normal J command, Just weather stations can be
     displayed on the map to eliminate the clutter of other packet stations.
     As of Ver 2.08 there is a Weather (alt-W) command which will cycle through
     each APRS weather station in turn and display the weather conditions for
     each one in a box on top of the screen.  The location of the displayed
     station is highlighted with a blue circle.  Whenever a new report comes
     in from the selected station, the weather window is automatically updated.

 REPORT BROADCASTS - The individual station weather conditions can be manually
     placed in the Beacon Broadcast from each station or automatically using
     the APRS WX option ($9) and ULTIMETER-II serial interface.  These reports
     are typically broadcast evrey 10 minutes.  The report is also available
     at anytime if an APRS user sends the WX station an APRS Query.

 STORM/HURRICANE TRACKING - Any station may place a storm or other object on
     his map, and the same symbol will be transmitted to all other stations
     in the net.  This is ideal for transmitting the location of a storm or
     Hurricane.  If the course and speed of advance of the storm is included
     in the position report, then the object will automatically be dead-
     reckoned on all screens until the next update.  Any station can update
     the location of the storm as information becomes available.  The updating
     station will automatically overwrite all posits in the net and will
     become the new reporting station for the object.  This prevents duplicate
     reporting and eliminates dependency on reporting stations that might
     disappear and not update an object that they originated.

 OPERATOR MESSAGES - The Point-to-point message capability can be used
     for operator to operator messages and alerts.

 COMMENTS   -  Transmitted along with each position report, there is a
     short comment field which can be used to report weather conditions,
     station status, intentions or other broadcast type information.

 VEHICLE TRACKING - APRS can track the movements of any mobile with a GPS or
     LORAN receiver properly interfaced to a packet TNC.

SKYWARN APPLICATION:   The map display has the capability of presenting both
a station's position and his course and speed.  APRS recognizes a special
weather report indicator so that all weather reporting stations are highlighted
in blue and the software recognizes that their course and speed indicators are
for wind reporting and not for station course and speed.  To date, I have not
standardized on the comment field, other than for the automatic ULTIMETER-II
interface.  This leaves the whole field open for a variety of Weather
reporting needs in free-format so that weather reports can be tailored to the
conditions at any time.  In addition to the brief weather report, the station
Beacon Text is also available for broadcasting additional amplifying info.
Any station running APRS simply calls up the LATEST display and sees the
current conditions from all stations on one screen.  Similarly, he calls up
the map display and sees the location of all stations and all specially
reported conditions.  Any authorized station can insert the location of any
special object on the map.  The location of that reported object or condition
is displayed on all screens in the network.  Even non-packet voice stations
making a weather report can be placed on the map (like an object) by another
APRS packet operator.  His station will appear similar to any other APRS
weather station, except that his report will include a marker indicating that
he was manually placed on the map by another operator.  We use APRS every
weekend for reporting the Chesepeake Weather and Traffic net.  Load the
SKYWARN.BK file to see the APRS network during one of these nets.

DEMONSTRATION:  To get an idea of how APRS works in a SKYWARN or other weather
reporting environment, load the backup file SKYWARN.BK using the ctrl-L
command.  The stations would normally be bright blue, but all stations fade
to gray if they have not been heard from in over 2 hours.  Use the P command
to pull up the position/weather reports and notice the format for the station
W3ADO.  That station is reporting the wind and temperature automatically
using the optional ULTIMETER-II interface.

ULTIMETER-II INTERFACE:  To permit automatic weather station reporting, APRS
includes an optional serial interface to the ULTIMETER-II home weather station.
(I hope to develop one for the HEATHKIT station too).  The optional APRS WX
interface accepts the serial data output of the ULTIMETER-II and puts the
information in your stations position/weather packet automatically for
unattended weather reporting.  (If you have a different home weather station
that has a serial data output, and can convince me that it is worth the effort
and widespread in the HAM community, let me know.) The rain report from the
ULTIMETER-II is for the present day, but APRS will use this information to
calculate the rain fall in the last hour.  I think this is more representative
for the typical emergency storm watch scenario that HAM radio is used for.
If you think of a better way, tell me.  I am not a weather fanatic and do not
have first hand information of the needs of ARES or SKYWARN.  With the
interface enabled, the normal APRS decaying of position/wx reports is disabled
and all weather/position reports are transmitted every 10 minutes.  This gives
6 reports per hour for continuity.  Of course, a WX/position report will be
transmitted by the APRS station at anytime, in response to an APRS query;
either an ALL NET Query (ctrl-Q) or a one station Query (by sending ?APRS in
a message).  If the wind speed is zero, then the direction is also transmitted
as zero.  (this is to prevent the station from appearing like a DF station).

REMOTE SENSORS:  Another advantage of the APRS system is the ability to
display information from remote environmental sensors.  We gave up building
our own sensors and are hoping to use the ULTIMETER-II home weather station
as an add on to all remote APRS digipeaters (without a PC).  Unfortunately,
however, we have not come up with a way to only transmit the data once every
10 minutes without having another microporcessor to parse the serial stream
from the ULTIMETER-II and only send it to the TNC once every 10 minutes
instead of the once every 5 seconds.  A simple edge triggered timing circuit
will not work because each 15 character record is often interrupted, even
between characters with significant time delays so that a simple once every
10 minute timer circuit is not suitable.  If this problem is solved then the
record will go out as a UI frame and APRS will grab it and display it.  The
position data will be stored in the TNC BText.  These stations will appear on
the map in Blue and their reports will be visible using the LATEST display
just like for the home stations.  It is planned to place an ULTIMETER-II node
at the location of every WDIE area digipeater used in the APRS system.
Currently weather nodes are under construction in Maryland at Point Lookout
in the south, Patuxent Naval Air Station, Chesapeake Beach division of NRL,
Annapolis, Baltimore, and NorthEast.  These sites will not only provide
automatic weather reporting capabilities all along the Chesapeake Bay area,
but will also form the backbone network for reporting the movement of radio
amateur's boats with GPS and LORAN.  Load the SKYWARN.BK file.

$$$  The ULTIMETER-II is available from PEET Bros 1-800-USA-PEET (872-7338)
     for $179 plus $20 for their Serial interface cable and $60 for the
     optional rain guage (self emptying, reads in 0.1 inches) plus shipping
     of $8.25.  (You dont need their $40.. software)  See adds in QST, CQ,
     Popular Mechanics, etc...

$    The optional APRS interface for the ULTIMETER-II is available from the
     author for $9 and may be ordered with APRS or as an option later.

                FORMATS FOR USING APRS WITH DUMB TERMINALS

    Since most of the features of APRS can be used even if a station is not
running the APRS software, this file describes the exact APRS formats so that
they can be manually entered from dumb packet stations.  This might often be
the case from lightweight portable packet stations.  Frequently the need for
the map display is not out in the field where the portable packet stations
are, but at the headquarters, or net control point.  The following paragraphs
suggest ways to use dumb terminals or non-PC computers and TNC's in an APRS
network.

    All APRS communication is done using UI frames.  UI frames are
transmitted with all the error detection capability of standard packets, but
they are not automatically acknowledged.  The only disadvantage is that if a
collision occurs or there is interference on the channel, the UI frame is not
automatically retransmitted.  In APRS this is not a problem because all
information is repeatedly and redundantly transmitted.

    UI frames can be transmitted easily from a TNC in two ways.  First, by
loading the TNC Beacon Text with a desired message, the beacon is repeatedly
transmitted as a UI frame.  The period of retransmission is set using the B
parameter.  Most standard TAPR-2 TNC's use 10 second increments so that a
B_E_6 actually results in a beacon once every minute.  A value of 60 is once
every ten minutes.  The BText is the primary method used by APRS to broadcast
one line messages to all stations.

     The second way to send UI frames is to enter CONVERSE mode directly from
the cmd: mode without first establishing a connection.  This is done simply
by using either the CONV or K command.  In this mode you specify your
digipeater path by using the UNPROTO command.  Once in UNPROTO CONVERSE,
everything you type is still transmitted as normal AX.25 packets, except that
lines are only transmitted once and acknowledgments do not exist.  As long as
you do not experience a collision, these UNPROTO packets are just as good as
the connected protocol and are very effective at broadcasting information to
many other stations at once.

TO ADDRESS:   One caution; since APRS operates in a broadcast fashion and
does not use a connected protocol, the TO ADDRESS is not required.  To help
ignore non-APRS traffic which might also be on the channel, APRS stations use
the TO ADDRESS field as a type of filter.  APRS will only recognize UI frames
transmitted to the broadcast addresses of ID, CQ, QST, BEACON, MAIL, SKYWRN and
APRS.  All other packets are ignored.  For this reason, you must place one of
these addresses in the TO ADDRESS field in your UNPROTO command.

APRS FORMATS:  Using either the BText or UNPROTO CONVERSE methods noted
above, APRS reports can still be transmitted manually.  To transmit a report
repetatively, enter it as a Beacon Text.  To report it once, simply type it
in the UNPROTO CONVERSE mode and hit carriage return.  The following formats
must be used exactly to have the desired effect at an APRS station.
Abbreviations are D for degrees (or DAY), M for minutes (Both lat/long and
time), h for hundredths (or Hours), N for North and W for West.  The
delimiter following the Longitude is used to indicate the type of APRS symbol
to be displayed (shown here as a $).  See the README.SYM file.


POSITION REPORT: To report the position LAT/LONG of your station you may
                 either use the abbreviated format for a fixed station or the
                 longer format for a mobile that includes the time of the
                 position and an optional course, speed, and comments.  If a
                 course is given with a speed of 000 then APRS assumes the
                 report is a line of bearing for direction finding.

   FIXED:   !DDMM.hhN/DDDMM.hhW$comments
   MOBILE:  @DDHHMM/DDMM.hhN/DDDMM.hhW$CSE/SPD/comments
   DF:      !DDMM.hhN/DDDMM.hhW$CSE/000/Cmmts (CSE indicates line of bearing)
   GRDSQR:  [XXnnyy]comments to end of line
   THENET:  TheNet ............!DDMM.hhN/DDDMM.hhW$........

WEATHER REPORT:  APRS recognizes the underline symbol character to indicate
            that the report contains wind direction and speed information.
            This plots the station in dark blue and prevents APRS from assuming
            it is a moving mobile station.  The remainder of the comment line
            can contain any other pertinent weather information.  In APRS version
            2.07 there is an optional automatic Home weather station interface
            which automatically inserts your weather conditions into your Posit
            report.  It includes the optional Temp and Rain fields:

            @DDHHMM/DDMM.hhN/DDDMM.hhW$CSE/SPD/T073/R000/WxStn fine day...

OBJECT POSITION:  To report the position of something other than your own
            station, the same format for a mobile object is used but it is
            preceeded with a nine digit object name.  For shorter names, the
            9 character field must be padded with spaces:

            OBJECT   @DDHHMM/DDMM.hhN/DDDMM.hhW$CSE/SPD/comments

BROADCAST:  Simply send anything.  If you are using your TNC BText to
            repeatedly send the same message, it is preferred to include
            the day and time that you entered the the BText in the text
            so that recepients can tell how old the information is.

            @DDHHMM/comments...

MESSAGE:    To direct a specific message to a specific station and have
            his bell ring and the message instantly flashed on his screen,
            use the following format, again padding the addressee call
            with spaces to a total of nine characters followed by a colon:

            W3XYZ____:one line message text......

            His station will acknowledge receipt with a responding message
            to you with only the letters ack in the message.

MSG ACK:    If an APRS station sends you a message line, it will be repeated
            over and over until you send a responding ack.  To send an ack
            to station W3XYZ, simply enter his call padded to nine spaces
            and a colon followed by the letters ACK# where the # is the line
            number tacked onto the end of his message line with a ({).

            W3XYZ____:ack3    (APRS versions after 2.08 require the line #)


USING AND DISPLAYING POSITION INFORMATION.  If all manual stations in an APRS
system carry a pre-printed map of the exercise or event area, not only can
they easily determine their own location for reporting, but they can also
plot the location of other stations and objects.  Usually, you do not need
the high technology of a GPS or LORAN receiver to know where you are.  Most
people can find themselves on a map and read the coordinates.  Then they
simply type them in to their BText and in a few minutes, everyone on the net
can see their exact location.  Similarly, by monitoring all of the APRS
beacons going back and forth, the dumb terminal user can still be equally
well informed of whats going on.

                          APRS DISPLAY SYMBOLS


     As of version 1.16, APRS supports 28 or more different display symbols
for differentiating objects on the map.  The obvious advantages of such
symbols is to show at a glance what type of packet stations are represented
by the various callsigns shown on the maps.  Another improvement is the
addition of two large symbols, one for thunderstorms and one for hurricanes
that cover a much larger geographical area.  Although these symbols are still
placed on the map at a very precise location, their large symbol areas are
much more representative of the very large objects that they represent!  The
maps are therefore much more realistic when used in the SKYWARN application.

     To make these symbols backward compatible with earlier versions of APRS,
the delimiter after the Longitude in the standard APRS POSITION report was
changed from the fixed (/) character to a variable SPECIAL character to
represent the different symbols available.  Printable ASCII punctuation
characters are mostly used to represent each of the display symbols.
Although these special characters are automatically inserted into the APRS
position reports, they are specified here for manual TNC stations.  Remember
that any TNC can still show up on APRS maps and displays as long as a
properly formatted APRS position report is placed in the TNC BText.  By
placing one of these special characters as the delimiter after the LONGITUDE
field, a station with only a dumb terminal can control his appearance on
other APRS displays.  For more information on manually formating APRS reports
using only a dumb terminal, see the README.DUM file.  The following table
describes the symbols available and the special characters used to represent
them.  Notice that there are several generic shapes without designated
descriptions, so that users can tailor their symbology to the particular APRS
net application.  If you have any suggestions for other symbols, please send
them in...


SYMBOL TYPE     SPECIAL CHARACTER  COMMENTS
------------    -----------------  -----------------------------------
AIRPLANES           '              Also for all -7 SSID's (heaven)
BBS                 [
CIRCLE              o              Default for NMEA reporting stations
DIGIpeaters         #
EMERGENCY           !
FIXED station       :              A club station, etc
GATEWAY             &
HUMP                )              Generic shape
TCPIP               }
Jay (J)             ,              Generic shape
Kross               +              More like a RED CROSS
Location            .              generic
MAILBOX             ]              PBBS's etc
NODE's              x
OBJECT              /              Default symbol
PORTABLE            ;              Looks like a tent
QTH                 -
RAIL                =              trains, etc
SHIP                ~              Also for all -8 SSID's (pieces of 8)
TRIANGLE            \              Generic shape
U U U               (              Generic shape
VEHICLE             >              Also for all -9 SSID's (engn, engn, #9)
WEATHER             _              (I used underline for ground conditions)
DX Cluster          %
Y                   Y              Generic shape
Z                   z              Generic shape
THUNDERSTORM        `              A large raincloud shape
HURRICANE           @              A large Swirl
SNOWFLAKE           *
(none)              G              No symbol for 4 digit Grid Square reports
(none)              ?              No symbol for 6 digit Grid Square reports
                                   (this preserves the ambiguity of G.S rpts)

Note that Weather stations will always show up as blue.  This overides all
other APRS colors.  Weather stations will also not be dead reckoned since
their course and speed indicates wind conditions and not station meovement.

                     WELCOME NEW REGISTERED USER!

ERRATA AND SPECIAL NOTES:  In most areas, I have built some simple maps to
cover most states.  These are just skeletons, but they give you a starting
point.  Use your local BBS to send out a query to APRS users in your state to
see if anuone else has already begun to fill in the map.  Here is a list of
OTHER REGISTERED APRS USERS IN YOUR STATE:

_________________________________________ _________________________________
Get in touch and see who will be the first to tackle a map of your area!

RV AND MOBILE HF NET:  We have begun a nation wide Boat, RV and APRS position
reporting net on HF using 7.085 and 10.151 MHz LSB. (Yes this is in the band!
10.151 MHz - 1700 Hz audio modulation is 10.149.3 RF energy.  This is the same
frequency as saying 10.147.6 USB, but the convention on HF is to specify packet
frequencies using the LSB convention to be compatible with everyone else on the
band)  I think that 30 meters is probably best for nationwide coverage.  Also,
if you are curious you can tune in the Naval Academy APRS net on a Navy freq
of 6260 KHz USB but they never go anywhere except in the summer May to August.
If you run an AEA or other TNC that does not use 1700 Hz center tones, then
tune 510 Hz higher on LSB and lower on USB.

BBS ADDRESS:  My BBS address is WB4APR @ WB3V.MD.  I have been a terrible mail
reader and often take weeks to download my mail, so do not expect a quick
response via packet, but do feel free to send me any comments or suggestions.
Similarly, I would like to add your return BBS address to my database in case
I have to send out any erratta info on the APRS program.


START HERE!!!:  You should read all of the following README files on the disk:

README.now  -  Tells you how to unzip the APRS distribution disk
README.NEW  -  Tells of important changes in the latest version
README.1st  -  This file
README.APR  -  General description and overview of APRS
README.HLP  -  Describes each of the APRS commands in detail
README.QIK  -  A quick summary of demonstrations and replays to impress you.
README.SAT  -  Suggested use of APRS for plotting satellite packet stationns
README.MAP  -  Detailed information on how to build your own maps
README.DF   -  Information on using APRS for triangulating beam headings
README.HF   -  Notes on the APRS HF tracking network
README.DUM  -  Info on APRS formats so you can use DUMb terminals and TNCs
README.RPT  -  A discussion on ways to use digipeaters to extend an APRS net
README.BBS  -  Suggestions to BBS's how to use APRS
README.WX   -  Info on using APRS for displaying weather information
README.GPS  -  Interfacing a Magellian or Motorola GPS to a stand-alone TNC
README.OPS  -  Suggestions on routine APRS operations
README.SYM  -  A table of APRS symbols and the symbol designator

Next you should customize APRS to automatically come up centered on your
favorite map screen.  If you are a registered user, first use the V command to
validate your callsign.  Once this is done, the yellow control panel will show
the VALID box.  Now set up the map to your center of activity.  Either your
home, or a WIDE area APRS digipeater.  Next set your desired digipeater path
using the Ctrl-V VIA command.  Finally, use Ctrl-C to save your configuration.
From then on, APRS will always come up ready to go on your chosen map area.

Non-registered users can force APRS to default to their favorite map area and
scale instead of the USA by simply using a DOS text editor to set the Lat/
Long/Range in the first three lines of the MAPLIST.MAP file to their selected
area.  Without a config file, APRS defaults to this area and all you have to
do is place your QTH on the map with the insert key, and you are ready to go.
Of course save the original center USA coordinates so that when you give out
copies of APRS to others, they will have the whole US map to start with.

MAPS! - I will try to generate "starter" maps for regions where there is APRS
interest.  These "starter" maps give you an initial structure for adding more
detail.  They have a rough state outline and maybe an interstate or two, just
to give you a starting point.  It is really quite simple to draw a map.  Using
just a state Highway map, it should only take you one evening to enter all of
the interstate roads and the important four-lanes; and another evening if you
have to do a lot of detail coast line or rivers.  Fortunately, everyone in the
state can use the results of your efforts!  I find that with just the interstate
highways and the important four-lane roads, you have a perfectly useable map
for most VHF packet operations.  You only need to draw more detail maps for
special events or applications.

PACKET POSITIONS ON ALL FREQS:  Finally, encourage all BBS's, NODES, Servers,
and stations in your area, to start placing their LAT/LONG in their beacon text
using the format: BT !DDMM.xxN/DDDMM.xxW/....comments.  As of version 2.05,
APRS will also plot the positions of stations reporting by Grid Square.  And
as of version 2.08, then !LAT/LONG can be anywhere in the BText.  This permits
THENET Nodes to add it to the end of their ID Beacons.  If all packet stations
get in that habit, then APRS will automatically plot a map of packet activity
on any frequency!

                        HOW TO MAKE YOUR OWN MAPS             (README.MAP)

MAP FILES:   To see what map files are available to the system, use the alt-M
command.  This command draws the boundaries of all map files and shows you the
areas covered by detail maps.  Some of these maps are very detail, and some are
just "starter" maps that I have made to give new users in those areas a basic
map outline from which to add their own detail.  Since I live in Maryland, you
will notice that we have a lot of detail maps already put together for users in
our area.  Notice how maps of finer detail can exist within the same area.  Zoom
into my neighborhood at 3910N 07636W and see my neighborhood detail using 1200
pixels per degree.  As of this date, there are five starter maps with little
internal detail.  These are for Texas, Illinois, California, The Carolinas
Georgia, Ohio/Michigan/Ontario and Arkansas/Miss.  See the section MORE ABOUT
MAPS at the end of this file for info on how to center, convert and spawn new
maps.  Slowly other APRS users are beginning to produce maps.  Here are some
good map makers:

W4NMK Dan Reilly,   Black Mountain NC
N4WJQ @ WA4TFZ.VA   Charlottsville VA
W9LZQ Kent Helman   Onalaska       WI
KD1E@N8NNN.#SEMI    Michigan
N3FKV DIck Campbel  Waco           TX
KD6MKS Mike         Silver Lake    CA
W7KKE @KA6EYH#nocal S.F. Bay       CA
KB5YRZ@N5SSY#METLA  New Orleans    LA
N4FOR Card Smith    Savannah       GA


Each Map file is put together using just a DOS text editor to list the ends of
line segments drawn point-to-point.  You can use any editor to prepare a map
file.  Simply use a chart that has lat/long references and select an origin well
beyond the upper left hand corner of the area you want to cover.  That point is
0,0 and all points are measured from there. (negative numbers are OK if you
later add points behind the origin, but the - is an extra character that slows
down file loading); similarly, an X value of 0 is not permitted since it is used
to indicate separations between line segments.  Choose a scale in pixels per
degree of longitude and latitude.  Since EGA graphics has a 350/640 pixel
resolution, I have found that 120 pixels per degree (2 pixels per  minute) is
excellent for state size maps.  I used 6 pixels per degree for the whole US.
To get down to the individual street level, I have used as many as 1200 pixels
per degree in order to resolve my neighborhood.  If you use too fine of a scale
then you are limited as to how far the map can extend.  Points with values
greater that 999 should be minimized and no values should be bigger than about
1100 or there is a chance APRS will crash on very zoomed-in maps.  The further
you zoom in, the larger the values become until you get an overflow error.  In
any map file, the first 8 lines define the origin and scale.  Comment text is
permitted on these lines after the data value and a comma.  See the example
map below for Colorado.

MAPLIST.MAP:   This file contains the list of all maps available to the APRS
program and decides which map is loaded for every location of the cursor.   It
also contains the default LAT/LONG, Range and GMT offset for your location.
For example, Eastern Standard Time is -5.  The program uses the default LAT/LON
to center the first map each time the program starts up (on unregistered users)
These values are NOT used when a saved backup file is loaded using the CTRL-L,
or when a registered user has saved his default values in his APRSconfig file.
So to force APRS to start up at your location, you can either change this
location in the MAPLIST file, or move the cursor to your location and use Ctrl-S
to save a backup file with you at the center, or if you are a registered user,
save a config file.  To change the default in the MAPLIST file, change the first
four lines to your area as soon as you like.  Keep a virgin copy of MAPLIST.map
so that if you mess up the file, you have a clean starting point again.  The GMT
offset is used to correct the raw time reveived from GPS/packet mobiles.  As
of version 2.05, you can instantly zoom out to the default map using the
Shift-End key.  This is useful for doing a quick hop across the country!

ADDING MAPS:   To add a map to the system, look at the MAPLIST.map file.  It
contains a list of all maps available.  Add a line that contains your
map-name, LAT, LONG and the Map Range.  The LAT/LONG are in decimal degrees and
describe roughly the center of your map.  The map range tells the system to
load this map if the cursor ever falls within that range of the center.
Actually it is a little more complicated.  The given map will not be used until
the cursor location plus the current range scale in all directions fully falls
within the boundaries.  This keeps you from being on a postage stamp sized map
of someone's neighborhood when you are zoomed out to see the whole US!  HINT -
so that your detail map seems to blend in with the next larger map, add enough
rough lines and points to your boarders to surround your fine detail area with
crude detail out to MAX Range beyond.  Then when the screen centers on a point
near the edge of your fine detail, your map doesn't just stop but includes
crude detail to all edges.

MAP HIERARCHY:  It is important to place maps in decending order.  The last map
in the list that shows the given cursor position will be used.  If a larger map
covering the same area as a smaller map follows it later in the list, then the
larger map will always be found last and will be used, instead of the desired
smaller map.  If maps overlap in your area, hit shift-Home to temporarly see
the map underneath (ver 2.05 and later).

MAP LINES:    Each line segment begins with 0,0 followed by the line color  and
line name, followed by pairs of x,y points using the scale you chose.   Values
are positive to the right and down.  APRS assumes the color red (4) is used for
secondary roads, bright red (12) for important highways, and green  (10) for
interstates.  I use light blue (11) for rivers and coast lines,  orange (6) for
city/county lines, purple (13) for special event routes, etc.  All of these
colors are recognized by the software for selectively turning on and off map
Features using alt-F.  The end of a line segment is simply the
0,0 which starts a new line.  After the last line segment, there is a special
0,-1 which indicates the end of the line information and the beginning of the
Labels list.

MAP LABELS:   Labels are drawn on maps at given lat/long coordinates.  The
labels are all listed at the end of each map.  Each label also has a  range
scale associated with it, so that not all labels are visible at all  range
scales.  As you zoom in to finer and finer detail, you can make more  labels
appear.  The first line in the labels list has a leading 0 and at least the
word "Labels...".  From then on to the end of the file, each line  consists of
4 fields separated by commas.  First is the label text (up to 12  characters
long) followed by the LAT, LONG and RANGE.  LAT and LONG must be  given in
decimal degrees.  The MAPFIX.bas program displays the location of the cursor
in decimal degrees for this purpose.  Labels are plotted right justified.  This
means they will be plotted to the left of the given point.  A way to visualize
how a label will appear is to assume the label has a following  period (.) and
that the period is the location where the label will be plotted.  Labels are
right justified so that they do not overprint station callsigns which are all
left justified.   Since absolute LAT/LONG reference is used, labels can be
transferred with out any change to any scale map.  You may decide to change the
range size so that the label shows up sooner or later on different maps.

EXAMPLE:  The following map file constitutes a trivial state map of Colorado.

The first 8 lines are the fixed format lines which define the origin and scale.
Next are the line segments for the state borders and for Denver.  Finally are
the map labels.  To see how this map looks, move the cursor to the center of
Colorado on the US map and page-down to the 256 mile scale.
  41.0, latitude origin    (   equates to 0,0   )
  110.0, long of origin    (in coordinate system)
  60, pixels per deg of lat/long
  39,Latitude of map center
  105.5,Longitude of map center
  200,MapRange
  4,min rng (APRS no longer uses this.  It now computes min range)
This is a comment line which can contain anything... more or less
  0,0
  6,Colorado state line
  59,0
  59,240
  479,240
  479,0
  59,0
  0,0
  14,Denver city limits
  300,68
  289,77
  300,85
  311,77
  300,68
  0,-1  (indicates end of map lines )
  0,Labels list.... etc (note that the characters 0-comma-LABELS are required)
  Colorado,40,105,200
  Denver,39,104,100

NOTE:  The 7th line showing a min range used to be important.  Starting with
a full scale map, each time you page-down (zoom in) you are doubling the value
of each pixel lat/long value.  If any of these numbers ever exceed the maximum
permissible value of 2 byte integer math (32,000) then the program will crash.
After version 2.04, APRS assumes that there will not be any data points larger
than about 1100 and will not draw your map to a scale that would multiply this
number too big.  This is why APRS will not draw the USA map smaller than about
32 miles.  Six pixels per degree for the USA map was a poor choice since the
largest point value is still under 400 or so.  So I could have used 12 per
degree and still been below 999.  This would have given me better resolution
and would have permitted zooming in to 32 miles.

MAPFIX.BAS:  This QBasic program may be used to test your maps.  It will quickly
display a single map and allows you to use the cursor and a special pointer to
identify individual map point coordinates.  It also has a read out of the cursor
in decimal degrees which is handy for locating labels.

MAPCNVRT.BAS:  This QBasic progarm may be used to convert any one map to a
different LAT/LONG origin or different Pixels-per-degree resolution.  Use it in
conjunction with the QBasic editor for piecing together lines from one map to
cut and paste into another map.

FINAL COMMENTS:  See the sketch above (not available in text file) which shows
how simple it is.  Most maps have LAT/LONG lines around the boarders.  If you
are using 120 pixels per degree for a state size map, then each LAT/LONG line
corresponds to a multiple of 120.  Simply mark on the boarders of your original
map these values 120, 240, 360, etc.  Then make a smaller template which
matches the size of one square of LAT/LONG lines.  Draw a finer grid of lines
every 10 pixels on the template.  Then to locate the coordinates of any point
on the map, simply orient the template with a major LAT/LONG square, and
interpolate the point within the grid on the template which represents a 10x10
pixel area.  Actually, if we all use 120 pixels per degree for state size maps,
then it is easy to transfer roads and lines from one map to another without
mathimatical computations.  For transfering objects from one map scale or origin
to another, Use the QBasic program called MAPCNVRT.BAS which will re-compute all
line points.  Then use a text editor to re-do the center LAT/LONG and range
lines and to cut and paste the necessary map labels on the end.

CAUTION: since many highway maps are Lambert Conformal instead of Mercator
projections, use the center square in your map for making the template to
minimize errors.  Further, be careful of highway maps that only have tick marks
along the boarders for LAT/LONG. If the map is not a Mercator projection, then
you cannot just draw a straight line from left to right connecting latitude
marks.  Longitude lines are straight on a Lambert Conformal, but not latitude
lines!

SPECIAL EVENTS:  Conversly, absolute accurracy is only important if there will
ever be a GPS or LORAN-C station involved in your net.  A map with little
relationship to true LAT/LONG is perfectly useable in all APRS applications
as long as all stations in the net are using the same map and no one is using
GPS.  So feel free to draw quick simple maps for special events even as small
as a few square blocks without worrying about exact LAT/LONG.  Objects on one
station screen will still be in the same location on all other screens!  Use
the Chess board example at 25N 90W to play chess on the air!  But GPS is
comming, be prepared!

                          MORE ABOUT MAPS PART 2

EXTRA EXTRA!!  Just found that ADC company that makes county maps for 7-11
stores is now making state map booklets which have a LAT/LONG grid on every
page!  The grid lines are 5 minutes apart which is exactly 10 pixels if you use
120 pixels per degree as I do for most APRS state maps.  This means that each
grid square is a 10x10 pixel area from which map coordinates can be typed
directly into a text editor without any drafting aids!  Simply note the grid
coordinates of the corner of each page in the book and start entering points!
Rumor has it that the comparable convenience map maker on the west coast is also
now making map books with LAT/LONG grids.

NOTES ABOUT STARTER MAPS:  The starter maps that I have provided use a  scale
of 120 pixels per degree and have an origin that is suitable for about a 400
mile square area.  This area usually covers from one to several states and is
good for area maps.  With the whole map visible, one pixel represents abt .25
mile resolution.  The first step in customizing maps to your area is to take
the starter map and start adding roads and features in your area.  Since all
maps in the APRS system are limited to a maximum of 1000 data points, however,
these large area starter maps can usually contain only the interstate roads,
the state lines, and major rivers and 4-lane highways.  This is perfect for
most VHF applications.  But as more and more people add detail closer to home,
smaller maps need to be "spawned" off to make room for more detail.  The
following sections describe how to spawn maps and convert lines from one map
to another.

MAP CENTERING:  Most of you do not live in the middle of a starter map and so
your detail will be off center.  To make a more pleasant transition as you
zoom into your area using APRS, you may want to simply change the center and
range of the starter map to be centered on your area with a range suitable to
the amount of detail you have added.  To do this, simply edit the line for your
starter map in the MAPLIST.map file to your desired center and range.  To keep
the original starter map for others to use, you may want to rename your map and
give it a new entry in the MAPLIST.map file.  As the number of points in your
map grows, you may need to throw out some of the points which are beyond your
area of interest.  See the next section on map spawning.

MAP SPAWNING:  In the figure above, map A is the original starter map with the
origin at O.  Using 120 pixels-per-degree resolution, all points within a
square area 8 degrees on a side (about 400 miles) can be resolved with pairs
of 3 digit numbers.  As the number of points in such a regional area map fills
up towards the 1000 limit, it is necessary to start new smaller area maps such
as B, C, and D above to permit finer detail to be added.  Spawning a new map
is easy.  Simply use a text editor to create a new mapfile and copy all of the
lines out of the original map that fit within the new map area. Then save this
new map and add its name to the MAPLIST.map file giving a center and range
appropriate to the new smaller area covered.  Now add new roads and features in
the area of interest.  Notice that since the same origin and 120 pixel-per-
degree scale are still used among all maps spawned from the same starter map,
lines and points can be moved among those maps by simply cutting and pasting.

MAP CONVERSION:  When it is desired to move lines and points from one map to
another map which has a different origin (X) or resolution, then use the
MAPCNVRT.BAS program.  First spawn a new map which contains all of the points
that are to be moved.  Then run the MAPCNVRT program giving the new origin and
resolution.  The resulting MAPTEMP.MAP file contains a copy of those lines and
points ready to be cut-and-pasted into the new map (Y) with the new origin (X)
and resolution.  This process is useful when creating finer detail maps of an
existing area and you want to transfer the interstates and larger map features
down to the finer detail map without having to re-do the data points.

                        APRS OPERATIONS NOTES

   The following discussionm may help you to understand the finer points of
operating an APRS net.  It covers the two categories of operations.  Routine
and Special event.  Also read the section on OBJECTS since the information
there applies to both cases.  The advantages of APRS are many, but there is
a price.  Since APRS uses a fixed digipeater path sometimes different for
different stations depending on geographic location, there is a lot of
duplication of on the air packets.  This assures that all stations in the net
are maintained up to date, but also proves to be wasteful during intense
operator-to-operator QSO's where this point-to-point traffic is still being
unnecessarily broadcast to all stations in the net.  For this reason, APRS
operators should always consider using TNC TALK mode (connected) to do
intense one-on-one keyboard QSO's.  Especially if a direct connect without
using APRS digipeaters is possible!

ROUTINE OPERATIONS:  The APRS default digipeater path of RELAY is ok for a few
users starting up an APRS net, but you will soon need to focus on a few good
stations to serve as WIDE area digipeaters.  Once you put up a few good wide
area digipeaters with the generic ALIAS of WIDE, the coverage of the network
can be extended significantly.  It is important to keep generic WIDEs well
separated (40 miles or more over smooth terrain) to minimize duplicate repeats.
Most users should be able to hit at least one of these WIDEs.  All users must
understand that they are responsible for setting their outgoing VIA path so
that their packets hit the intended area of interest.   Unlike normal CONNETED
protocols which return ACKS via the reverse path of incomming packets, APRS is
an unconnected broadcast protocol only and each stations packets will only go
via the outgoing path set up by that station.

    Those stations between WIDE area digipeaters only need to use the single
hop of WIDE and their packets will go in both directions.  Stations that can
only hit one WIDE area station may set the path of WIDE,WIDE without any
conflicts.  Paths of WIDE,WIDE,WIDE should be avoided for routine operations
because it folds back on itself.  The same area can be covered by using
WIDE,WIDE,W3XYZ where the unique call of the third digipeater is specifically
specified.  If you think about it, stations at the end of an area can specify
a pretty long string of digipeaters since the path is linear.  Stations in
the middle can only specify a symetrical double hop with WIDE,WIDE before
they have to begin favoring one direction or another with unique calls.

     Remember that the general condemnation of multiple digipeater hops in
the packet community applies only to connected protocols.  This is because
the probability of success goes down drastically because all ACKS must be
successfully returned or all packets are repeated.  This is NOT a problem
with APRS.  Don't feel guilty of using three hops for APRS at all, since
there are no ACKS, and if a packet gets a collision, so what, it won't be
automatically repeated.  (Of course if you do a lot of one-line messages
between operators, you will experience the gradual buildup of collisions due
to the quasi-ack process built into APRS for operator messages).  But
operator messages are a secondary function of APRS, not primary.

OBJECTS:  As noted previously, anyone may place an object on the map and all
other stations will see it.  In their systems, on their P-list, the object's
position report will be marked with the last three letters of the station
that is currently uplinking that position to the net.  A neat feature of APRS
is that any station that has more current information on the location of that
object can update its position by hooking, moving the cursor, and then
hitting the insert key.  Now this new station begins uplinking the new posit,
and all stations, will update their P-list entry for that object INCLUDING
THE ORIGINAL UPLINK STATION!  The new position overwrites the old one so that
the original station will now no longer uplink it.  This came in handy during
hurricane tracking.  Who ever had information on the latest NWS EMILY
position, uplinked it and everyone then always saw the latest storm track
without anyone in the net being dependent on any one station for updates!


SPECIAL EVENTS:  Let me use the Cycle Across Maryland (CAM) bike tour as an
example of a special event which took a lot of daily APRS coordination.  We
had two of three relief vehicles configured with GPS packet transponders.
These were assembled in cake pan enclosures for duct-taping to the roof of
any vehicle.  The uside down cake pans are reasonably aerodynamic and support
both the GPS antenna and a 19 inch 2 meter whip.  A single power cable
extended down the windshield and was clipped directly to the vehicle battery.
The package could be moved to another vehicle in about five minutes.  The
cake pan included only a walkie talkie transmitter at about the one watt
level.

    Since we only have two WIDE area APRS digipeaters in the state, and the
CAM tour never went near them, we were dependent on home stations all across
the state to serve as digipeaters for the event.  The GPS packages were set
to digipeat via the WIDE,WIDE path.  By setting the alias of all home
stations along the route to be WIDE, the vehicles were never beyond range of
at least one WIDE station.  Since the outgoing GPS packets were set up for
WIDE,WIDE, the second digipeat was always picked up by one of the existing
permanent WIDE digipeaters so that stations throughout the state could see
the position of the one watt GPS units!  We were looking for home stations
about every 10 miles.  Of course, as soon as a station was passed and was not
longer in direct contact with the GPS units, it was important to remove the
WIDE alias to minimize duplicative repeats.  For this seven day event, home
stations were organized on a nightly basis.  Assigned stations would be WIDE
for a whole day so that operators did not have to be home during working
hours.  As an added technique, we also set up both GPS units with the alias
of WIDE so that they would also help digipreat each other along the trail.
The disdavantage of this technique was evident as both vehicles returned to
the evenings command post (also WIDE) and you had three WIDE digipeaters in
100 yards of each other!  It was noisy within local simplex range of that
site, but stations all over the state still saw the packets via the permanent
WIDE digipeaters.  Eighty percent of the home stations used as WIDE
digipeaters had never even heard of APRS.  They simply heard about the need
for home packet stations and only had to change their ALIAS (and frequency)
as directed by local announcements posted on all area BBS's.

     The event was an exciting success!  Occasionaly there were not enough
HAM voice operators per day to have HAMS in all of the relief vehicles.  When
ever a shortage occurred, the HAMS were removed from the GPS vehicles and
assigned elsewhere.  The location of the GPS vehicles were always known by
net control via the APRS system so the need for a HAM rider was not necessary
and in fact, only took up valuable space.  Whenever voice communications were
needed with the GPS relief vehicle, a mobile HAM was directed to the location
indicated on the APRS screen.

EMISSION CONTROL:  If there are only a few APRS stations involved in an event
but there are lots of APRS observers on frequency, then the observers can set
their transmitter off using the CTRL-X command.  That way they minimize the
QRM on channel.  While the transmit function is disabled with CTRL-X, a one-
time transmission can be forced each time the T key is pressed.  The T key
enables one cycle of APRS transmission which may contain up to four packets
containing your Beacon, Position, Objects, or Messages.

LOAD SHARING:  Since any station can take over reporting of any objects, one
approach is to let only one station hook every symbol that comes in and then
he becomes the reporting repsonsibility.  The original station that uplinked
the report in the first place will fall silent when it sees the report
comming from the designated Net Control station.  This way all positions are
reported by only one station on frequency, although all other stations can
still update the positions as needed.  Remember that the last station to
report the position of an object will be the one that continues to report it!                      USING APRS FOR DIRECTION FINDING

    APRS is an ideal tool for rapidly triangulating fixes to locate a hidden
transmitter, an interfering signal, or for tracking balloon payloads.  APRS
instantly plots vectors from all stations making a signal report and the
intersection of these lines of bearing indicates the location of the target
signal.  To see a sample, load the file named FOXDF.BK into APRS and see the
results of our DF on a constant carrier on our local 145.05 packet frequency.
The bearings from W3ADO and W3DTN were actual measured beam headings.  The
third bearing from N3BFO was added to the file to show how great it would be
if we had three stations reporting instead of just two.

     To accomplish this triangulation, each participating station simply
enters his bearing to the target using the Ctrl-B key.  This sets his
position report to include the bearing as his station's course and sets the
speed field to zero.  This alerts all APRS stations that the course field is
being used as an antenna bearing indicator.  As soon as two or more stations
are reporting a line of bearing to the target, everyone can predict the
intersection of the lines by pressing the X key for a cross fiX.  As a
further aid, the R key can be used to superimpose a set of range rings on the
screen for estimating distances for subjective analysis of signal strnegths.

     Even for stations not running APRS, their lines of bearings can be
quickly entered by any one APRS station using the alt-A key which adds them
to everyone's map in real time.  In this case, simply include the bearing in
the course field and set the speed to zero.  A Direct entry feature has also
been added (using the alt-D key) for placing a reporting station on the map
by entering his numeric LAT/LONG.  This makes plotting of distant stations on
the map easier without a lot of cursor movement.  This feature is useful when
taking reports by voice over HF for example during a balloon tracking event.
Non APRS packet stations can also automatically report their lines of bearing
into the system by simply entering a beacon text in the APRS format with
their line of bearing.  See the README.DUM file.

    Finally if a mobile fox-hunter is equiped with GPS or LORAN, his
movements will also be tracked so that he can be vectored into the target's
location.

    As a further note, the line of bearing feature can be used routinely by
any stations using a beam to indicate their beam heading to all other APRS
stations.  For this application, the user has the option of specifying the
beam heading to be permanent or to default back to zero after two hours.
This default after two hours was added to eliminate old DF headings which
could confuse direction finding.

    Eventually I want to add a signal strength contour display so that single
stations can report simply their relative signal strength on the jammer, and
intersecting circles from each station can also be used in the triangulation
process.  Feedback on this application of APRS is welcome.

    I am also willing to add the serial port interface between APRS and any
DF unit which can output target bearings via a serial port.  One such
manufacturer is already communicating wih me about doing this.  With this
interface to doppler DF systems, for example, DFing can be done in seconds!       USING PBBS's AND INCLUDING APRS PROTOCOLS IN BBS and NODE SOFTWARE

    One thing we have learned in maintaining an operational APRS net on 145.79,
is that it is very useful for all stations to include in the comment field of
their position report the address of their home BBS!  Then any station on the
APRS frequency immediately learns how to send that station a lengthy packet
message.  If your TNC supports an internal BBS, it is also useful to leave it
on and include its unique address or SSID in your comment field so that stations
can access your PBBS even while you are running APRS!  A few stations sending
keyboard messages into a PBBS on the APRS frequency is not objectionable since
the number of packets are small and at typing speed.  I encourage all stations
to operate their own PBBS maildrops on the APRS frequency; but please do not
use the PBBS's to post messages for others who must read the message over the
air.  All stations should avoid any other general computer to computer exchanges
which would block the frequency for large blocks of time.

    The remainder of this file is intended for BBS SYSOPS and the writers of
BBS and NODE software.  Please consider the following advantages to including
APRS protocols in your station operation.  Since APRS allows stations to see
the network topology in real-time, it is ideal for determining the locations
of all neighboring BBS's and NODES.  If BBS's and NODES simply included either
the LAT/LONG or GridSquare in a periodic UI frame, all users could see where
the system is located.  For permanent  sites such as BBS's and NODES, this
beacon could probably be transmitted once every hour or so.  As of APRS version
2.08 the !LAT/LONG format can be placed anywhere in the BText.  This was to
accommodate THENET Nodes and some BBS software where the beginning of the BText
is pre-loaded with something already and the !LAT/LONG can only be appended to
the end.  The exact format of the UI frame should be as follows:

    BBSXX>APRS:!DDMM.xxN/DDDMM.xxW[comments as desired to end of line
    BBSXX>APRS:[GRidsq]Comments to end of line

    For BBS code writers, this process can be enhanced by making the BBS respond
to APRS Query packets.  One of these packets is transmitted whenever an APRS
station initializes his program.  On receipt of an APRS Query packet, all
stations on frequency set a two minute random number timer and respond sometime
in the next 2 minutes with their location.  This way, any APRS station can
obtain the location of all stations on the frequency soon after comming on
frequency.  The format of the APRS Query packet is W4XYZ>APRS:?APRS?.  By
including the code in NODE and BBS software to respond to APRS Querys, the
periodicity of the APRS position beacon can easily be set quite infrequently
since stations can request the BBS position at any time.  For those concerned
with physical security, the grid square position report can be used which is
ambiguous to 3 miles or so instead of the LAT/LONG posit accurrate to 60 feet.

    I have one other request to BBS SYSOPS.  Since APRS contains a BEACON
parser to display to users all BEACONS heard on frequency, this is an excellent
way for stations to capture MAIL-FOR beacons.  APRS stations simply call up
their LATEST BEACONS display and see if there are any BBS's reporting mail for
them.  Unfortunately, the parsing algorithm in APRS only recognizes BText which
occurs on the same line as the packet header.  MAIL-FOR which is listed on a
second line after the header do not show up in the APRS system.   For this
reason I would like to request BBS SYSOPS to modify their MAIL-FOR beacons to
keep the beginning of the MAIL-FOR list on the same line as the packet header.
By allowing APRS stations to see mail lists without even logging on, you are
helping reduce congestion on the channel.  Presently, most stations do not see
MAIL-FOR beacons because they scroll off the screen too rapidly.  APRS grabs
all BEACONS heard and retains them.

     Please play with the APRS software and load some of the backup and
demonstration files included.  I'm sure you will find APRS to be an exciting
new capability for packet radio which can make packet radio much more responsive
in real-time communications.

     Finally, ambitious code writers could add code in their BBS's to capture
all APRS position reports heard on frequency.  These reports could be retained
in a file and be made available to local users.  One of these files, if
downloaded, can be loaded by APRS users to display the locations of all stations
ever heard on the frequency!  Talk about preparations for emergency comms!

BBS FORWARDED POSITION REPORTS:  Since we already have a worldwide packet
network of BBS's which have the ability to forward a packet message anywhere
in the country, I would like to see a standard message format built which would
permit a mobile, roving packet station to report his location back to his home
BBS.  Imagine that this mobile station simply posts a message on any nearby BBS
which contains his position and the routing for his home BBS.  That packet
message would be forwarded via the normal BBS network and arrive at the intended
destination whereupon the destination BBS would in turn send out an APRS beacon
reporting that unit's position even if he was thousands of miles away and on
the road!  All of his buddies (or his wife) would see on their home computers
his latest position automatically which was actually relayed through the packet
BBS network.  As with any APRS position report, the beacon periodicity would
decay from 10 minutes to once every few hours as the position report got older.
The format for such a position report for WB4APR might be as follows:

SEND:    SP APRS @ W3IWI.MD.USA                   Send command with Routing
Subj:    !3858.11N/07629.11W/040/010              LAT/LONG/CSE/SPD
Msg:     Be home at 1200 Saturday.                Comment field up to 40 chars
         /EX

On receipt of such a message, the receiving BBS (W3IWI) would form an APRS
station reporting UI frame and transmit it periodically as follows:

W3IWI>APRS:WB4APR   @051937/3858.11N/07629.11W/040/010/Be home at 1200 Saturday

As with all APRS packets, this packet would be transmitted once, then 16 seconds
later, then 32 seconds later, then a minute later, and so on.  This doubling
ot the packet period after each transmission decays very repaidly to only 6
packets in the first 10 minutes, 3 more in the next hour and only 3 more in an
entire 24 hours!  Since the packet took hours to get to the BBS in the first
place, it might be more appropriate to start off with an initial period of one
or two minutes.  This is not such a load!  This would only be 9 packets in the
first day and only 1 in the second!  When the period is greater than 24 hours,
the message is deleted from the system. People on the road reporting home would
probably send a new message every 24 hours anyway.



                    GPS or LORAN INTERFACED TO APRS


     As of APRS version 2.0, this file consists of two parts.  The first is
new and describes the addition of an optional ($9) NMEA-0183 interface to the
APRS software so that any standard GPS/LORAN can be plugged directly (almost)
into a serial port of a computer running APRS and the computer will not only
plot the position of the station and its movements, but will also transmit
those position reports into the APRS net.  This feature was added by popular
demand from all the James Bond guys out there that wanted to see themselves
driving around on their laptop.  The problem is that most laptops only have
one external serial port, so you must give up the APRS packet position
reporting if you want to see yourself.  One advantage of this mode of
operation, though is that it gives you something to play with if you already
have a GPS and no one to play with on APRS yet.  It is also ideal for boats
and RV's that have room for a full size PC with two serial ports.  With
version 2.00 and later there are three operational configurations:

     TNC only  - 1 Serial - Normal APRS for tracking other stations
     TNC/GPS   - 2 Serial - Normal APRS but your position update is automatic
     GPS only  - 1 Serial - Tracking yourself (no other stations appear)

Operation of a GPS with the optional APRS interface is automatic.  Be sure that
you set your serial port to the NMEA-0183 baudrate.  NOTE!  NMEA-0183 and
RS-232 are not exactly compatible.  Although they are the same sense, NMEA is
a 0 and +5 volt signal, whereas RS-232 is a + and - 3 volt signal.  A direct
connection may work with some LAPTOP computers that themselves cheat a little
bit on the specification, but it may not work with most other serial
interfaces without a -V pulldown resistor.  Often a 5k resistor tied to the
unused TXD data line will suffice to provide the - voltage.  APRS scans the
interface data looking for a GLL/GGA/RMC and VTG data format to extract
position information.  The data on the NMEA interface is continuous and
refreshed every second.  In order not to saturate an APRS net or to overload
your disk storage with one second updates, APRS will only sample the data at
a minimum of once every 10 seconds.  This is still too rapid for transmitting
at 1200 baud on a shared packet channel.  We have found that 30 seconds
updates are OK for special events when there are only one or two mobile APRS
stations.  As more and more stations go mobile with GPS/APRS, 1 minute or 2
minute updates are more appropriate.  To further reduce channel loading, APRS
will decay the period when the station is not moving.

APRS OPTIONAL NMEA-0183 INTERFACE:  The optional COMM port interface to APRS
for direct connection of any NMEA-0183 device (GPS or LORAN) is available to
registered APRS users from the author for $9.  It can be purchased with
registration or as an option later on.

NOTE:  A version of APRS is available that is plug compatible with the MAGNAVOX
1105 SATNAV system.  This is a 1970's vintage TRANSIT SATNAV system which has
both LORAN and SATNAV integrated together in the same box.  This unit is found
on many US NAVY ships.  It sends position updates in a very verbose protocol
once every minute.  This is the system used on the Naval Academy boats.



          TNC INTERFACE TO GPS or LORAN-C FOR MOBILES WITHOUT PC's

     This section describes how to interface a GPS/LORAN device directly to
a TNC without a PC in the middle so that very small and compact tracking
devices can be assembled for tracking moving objects.  Typically packages
about the size of a cigar box can be assembled including batteries and
antennas.  APRS is compatible with almost all naviagtion devices that have an
NMEA-0183 serial data output.  The only GPS that I have seen that does not
have this national standard is the Rockwell engine and the SONY Pixis.  The
problem, however, is that many GPS or LORAN-C devices do not give the user
the ability to modify the periodicity of the data reported via the interface.

In most devices all navigation data is continually updated about every second
at 4800 baud.  This is far too much data to transmit over a shared 1200 baud
AX.25 packet link.  Fortunately some devices do permit the operator to
specify not only the reporting rate, but also what data formats are included
in the reports.  I have seen some LORAN devices that have a separate
"printer" port which can be configured by the user to output a report once
every N minutes or even hours.  Unfortunately, most users manuals I have
peruised in my local boat store do not make it immediately obvious what the
user configuration options are.  We have found two GPS engines which are
designed for the experimenter.

1.    The Magellian OEM 5000 circuit board that I use is a GPS engine on a
3.5 by 7 inch circuit card that costs about $445 and produces RS-232 output
in NMEA format and requires only a GPS antenna and 12 volts at 250 MA input.
Call Emiel Yakoub at Magellian 960 Overland Ct, San Dimas, CA 91733, phone
714 394-5000.  Since it is an OEM card, it has full user programmability.  It
can be set to output any of the dozens of NMEA standard formats at any
periodicity between 1 second up to 5 minutes.  My APRS software recognizes
four of the NMEA-0183 formats:

   $GPGGA - for position and height  (no loran equivalent)  ] Use only one
   $GPGLL - for position only        ($LCGLL for LORAN)     ] of these two
   $GPVTG - for velocity and course  ($LCVTG for LORAN)
   $GPRMC - Posn, Course and speed   (Has all but height) (not in Magellian)

2.  Tom Clark (W3IWI) has found that the Motorola OEM prototype card also has
user programmability of the NMEA outputs and can be slowed down to APRS
application rates for direct connection to a TNC without the need for a
computer in between.  This card includes the RMC message which contains
everything for land mobile in one NMEA sentence.  TAPR has bought a 100 lot,
but we are still trying to get individual cost and availablity information.

     An automatic vehicle tracking system can be assembled by simply
connecting the RS-232 output from the GPS directly into the TNC and setting
the periodicity to 1 minute or more.  The TNC must be placed in UNPROTO
CONVERSE, and from then on, every minute a GPS position report will be
transmitted.  The APRS software will decode the raw NMEA position reports
above and plot the station on the map!

MAGELLIAN CARD OPTIONS:   Since this card was designed for the OEM market,
for the individual purchaser it is a good idea to pay the additional $60 for
their  development kit consisting of some excellent PC software, the
technical manual, a wall power supply, RS-232 cable, Power switch, and short
SMB to TNC adapter cable.  Then all you need is an antenna.  They sell a $130
external "egg" antenna with built-in LNA for operation through either 18 or
25 feet of cable.  This cable is terminated with a TNC connector, that is why
the development kit includes the SMB/TNC pigtail.  OR you can purchase their
$60 passive antenna which has its own 6 inch SMB pigtail for direct
connection to the circuit board.  This antenna is a 1x1x3 inch weather proof
antenna like you see on their handheld GPS units.  Using this antenna (or a
1.5 inch paperclip stuffed into the SMB antenna jack) obviates the need for
the SMB/TNC pigtail ($25 separately) so that you might be able to do without
the development kit if you really want to be cheap.  Since the circuit card
has no display, it can actually be mounted in a weather proof container right
at the antenna (or paperclip).  Only 12 volts and RS-232 need to come down
inside your vehicle.  Yes their $60 passive antenna is quadrifilar helix
antenna with true hemispherical coverage, but a 1.5 inch ground plane antenna
is just as good as long as you are not interested in good 3D altitude fixes.
Overhead satellites are not used for 2D fixes, but are used for 3D fixes.  I
leave my card on 2D all the time since 3D requires 4 vice 3 satellites, and
the 2D fix is not as good while running 3D.  Also, altitude is measured
against DATUM which is not necessarily SeaLevel.  So unless you are carrying
DATUM charts, (or flying) the altitude figure is of little value.  The
Magellian cannot output an altitude above 999 meters except in a propriatery
NMEA sentence which I have not yet included in APRS. (should take me an hour
or so to do it. If you are going to do balloons, let me know).

GPS ENGINE SET UP:  Follow all Magellian instructions for initializing your
GPS engine using your PC and their NAV program.  After the system is running
and producing fixes, send commands to turn off all outputs one at a time and
change the periodicity for the position and velocity reports from once a
second to a slower rate as shown below.  An alternate startup procedure is to
simply apply power, attach an antenna, and wait an hour.  The GPS will
automatically aquire satellites and be operational without any external
initialization after being exposed to full sky.  (this precludes needing a
laptop if you can spare the time).  Using this method, there will be no
outputs until you send the GPS card the following commands to set up the
reporting rates for position and velocity.  These commands may be sent from
any dumb terminal as follows:

$PMGLI,00,B00,7,A  (for GGA GPS position only)       Where 6 = 30 Secs
$PMGLI,00,B01,7,A  (for GLL LORAN position only)           7 = 1 Minute
$PMGLI,00,EOO,7,A  (for course and speed with either)      8 = 2 Minutes
                                                           9 = 5 minutes

     Each line must end with a carriage return-linefeed.  The GPS engine
gives no responses to commands, other than doing what it is commanded.  You
might try a value of 5 which is once every 10 seconds as a test to be sure
the GPS card is recognizing your commands.

BATTERY BACKUP:  Be sure to add the battery back up supply so that the card
can be turned off without having to re-initialize every time.  I use a simple
9 volt battery, diode isolated from the main supply rather than bothering
with the special 3.6 volt lithium memory cell suggested.  The GPS card has a
12 volt input and a separate ON/OFF line.  With the diode isolation of the 9
volt battery, the on/of line detects the loss of the 12 volt supply, and
powers down the GPS engine.  Current drain drops to microamps, and the 9 volt
supply through the regulator keeps all memory backed up.  An Alkaline battery
lasts about 6 months with the GPS off 99% of the time; longer if the GPS is
powered up longer.

TNC SETUP DETAILS:  Unfortunately the simple direct connection from the
Magellian GPS card to the TNC is slightly more complicated because they do
not output the RMC sentence which contains everything needed for APRS in one
line.  To see Course and Speed from a Magellian, you must enable both GGA (or
GLL) and the VTG sentence.  These two sentences are separated a few
milliseconds and force the TNC to generate two packets, one right after the
other.  This is a problem if a digipeater path is used, because the
digipeater will begin digipeating the first position fix packet and cover up
the trailing velocity packet.  To solve this problem, since most applications
require a digipeater path for longer ranges, the sending TNC needs to be
instructed to send packets not on receipt of every carriage return, but on a
timing function.  Set CPACTIME ON and change the SENDPACK character from $0D
to anything else (say $01).  This way, both the position fix and velocity
lines will be sent together in the same packet one second after the last
character is received from the GPS.  This packet, containing two frames, will
then be digipeated all together by the digipeater with no break in between.
If you use the Motorola which inplements the RMC sentence, this double packet
problem does not exist. (Even if you also turn on GGA so that you can get
altitude for a balloon, the problem is not significant, since you will not
need a digipeater for a balloon!).

LINEFEEDS and FLOW CONTROL:  Since the GPS is sending each line with a CR/LF
on the end, your TNC will always end up placing the superfluous linefeed at
the beginnning of the next packet.  To defeat linefeeds, set LFIGNORE on.
(for the non-standard Kantronics products, use Linefeed Supress, LFS ON)
Similarly, your terminal program must send CR-LF on each command to the GPS
card.  When you try to talk to your TNC with CR-LF, you will experience a
lockup condition since the extra LF will look to the TNC like the beginning
of a new command line and will hold off all TNC output.  To overcome  this
problem, set FLOW OFF.  Here are the commands which must be changed from
factory defaults for most TAPR-2 TNC's:

  ECHO OFF,  FLOW OFF,  LFIGNORE ON,  CPACTIME ON, SENDPAC $01

UNPROTO-CONVERSE-MODE:   And now for the last problem; keeping the TNC in
converse mode.  TNC's always default to command mode when turned on.  Until
the manufacturers put an UNSTART command in their TNC to cause it to power up
in Unproto-Converse, you must either keep the TNC permanently turned on after
setting converse mode, carry along a terminal to issue the CONV command, or
try to make a firmware patch to the TNC code.  Transparent mode could be
used, but the monitor function does not work in transparent mode and the TNC
can not then be used for receiving APRS packets.  Fortunately, Howie
Goldstein who wrote the original TAPR-2 code, identified a software patch to
the DRSI version of the ROM that will power up in UNPROTO converse.  This ROM
should work in most TAPR-2 clones.  I have used it in the MFJ-1274, and it
should easily work in the PACCOM Tiny-2.  I have asked DRSI to make this ROM
available to amateurs at a nominal cost ($27).

DUMB TERMINAL SETUP:  So I can see the command that I am typing into the GPS
card, I configure my terminal device as half duplex.  The GPS also needs the
CR/LF sequence at the end of each command, so I set the terminal to translate
CR to the CR/LF sequence.  In order to use the same terminal with the TNC,
then, that is why I turn ECHO and FLOW off in the TNC.  My GPS/TNC box has
one DB-9 serial connector and two switches to select whether the terminal is
talking to the GPS or the TNC, and the second switch to enable the data
output from the GPS to go into the TNC after all configuration is complete.

SYMBOLS:  Starting with version 1.17, APRS now has 28 or more different
symbols for packet stations or objects placed on the map.  Since a simple
TNC/GPS tracking combo does not have the advantage of a PC running APRS to
format the APRS position report, I had to make two kludges to permit the TNC
alone to designate the desired display symbol.  First, APRS will assume that
all stations outputting direct NMEA data that have a -7, -8 or -9 SSID are Air,
Marine, or Mobile platforms.  Secondly, any of the APRS symbol designation
characters can be placed at the beginning of the TNC BText surrounded by {}
braces.  Once the BText with that symbol is received, the station will then
appear with the proper display symbol.  See the README.SYM file for details.

OPERATION:  With the special UNPROTO start-up ROM, and after initialiation
the other TNC parameters once, all future tracking evolutions are initiated
by simly applying power to the GPS/TNC/Radio.  In over 6 months of daily
operation, I have never had to re-initialize the GPS engine. (The seventh
month the 9 volt battery died!).  Without the special ROM, every tracking
evolution requires applying power, turning on a dumb terminal, and sending
the TNC the CONVERSE command.  Then the terminal can be removed or turned off
until the next activation.  If you do not have the UNSTART ROMS, be careful
if you use a battery supply of C or D cells with spring loaded battery
holder!  A bicycle equipped with this system reset the TNC after hitting the
first bump, and there was never time to stop and reset the TNC until the race
was over.  This shows the problem of the TNC not having a power up CONVERSE
mode in it!

We have assembled a nmumber of these GPS/PACKET tracking devices.  In fact,
the 7 inch by 3 inch Magellian card fits nicely against the inside cover of
the MFJ 1270 or 1274 TNC.  The only evidence that the TNC is GPS equipped is
the kludge on the backpanel to hold the GPS antenna connector and the
presence of the two switches added to the front panel to select whether the
external terminal device is talking to the GPS or TNC, and to enable or
disable GPS packet reporting.  Other smaller packages have been made using
the PACCOM and DRSI TNC's and the TTL only model of the Magellian GPS card
which is only about 5 inches by 3 inches.  I shy away from this card for the
casual experimenter because of the absence of any data or power supply
buffering.  One wiring error or static charge and you have blown a $395 card!

The $445 model with onboard 12 volt regulators and RS-232 buffers is much
more forgiving.

At your next club budget meeting, instead of throwing another $800 at the
repeater monster, buy the components to build a GPS/TNC tracking device in to
a cigar box size package.  Then at all future public service events, you have
a package with whip antenna on top that can be duck-taped to the top of any
vehicle for automatic vehicle tracking.  Let your imagination roam!This file is README.NOW

APRS consists of the APRSxxx.EXE file along with dozens of .MAP and .HST files.
Everything is ZIPPED up into a single APRSxxx.ZIP file.  Included on this disk
is also a copy of PKUNZIP to allow you to unsip the file onto your disk.  Once
you Unzip it, and if you want to reduce space, you might consider deleting some
of the track history files which are nice demo's, but not necessary for APRS
operation.  Without some of them, everything fits in 720K.

TO INSTALL APRS on your SYSTEM:              DOSprompt COMMANDS
-------------------------------------------- --------- ------------------------

1.  Create an APRS directory on drive C    - C:>       MD APRS
2.  Change Directory into that directory   - C:>       CD APRS
3.  Put this disk into B: and change disks - C:\APRS>  B:
4.  Unzip the APRSxxx.zip file onto C      - B:>       PKUNZIP APRSxxx.ZIP C:
5.  Change to C drive and execute APRSxxx  - C:\APRS>  APRSxxx
    a. Give your call and other info as prompted.
    b. Move cursor to your exact QTH using arrow keys and PgDn (shft-PgDN)
    c. Hit INSert key and answer QTH questions
    d. Use V command to enter your validation number
    e. Use ctrl-V to set your VIA Digipeater path (needs TNC to be connected)
    f. Move and center map to your area of interest and prefered range scale
    g. Save a config file using ctrl-C  (repeat steps e - g at anytime)
    h. Have fun! READ all the README.xxx files!

6.  If there are anyother files on your APRS distro disk, then they are newer
    than the ones in the ZIPped file.  IF PKUNZIP detects these new files, it
    will ask if you want to overwrite them, answer (N)o.  If it does not detect
    them, then after the UNZIP process has placed everything in your APRS directry
    and copy these remaining files (probably new maps or updated readme files)
    from the distro disk into your APRS directory.

                      HF APRS BOAT AND RV TRACKING NET

    We are currently operational on what I hope will become a national HF
APRS position and status reporting net.  The two frequencies so far are 7.085
and 10.151 MHz LSB.  Yes, I know that 10.151 is out of band, but the packet
signal (at -1.7 KHz) is not.  I use the LSB convention in specifying the freq
to be compatible with all other packet channels on the band.  If you are
really that concerned and have a bad radio which is not truely SSB, of course,
you can operate on 10.147.6 USB which is exactly the same frequency!  But
you will have to explain it to everyone who doesnt understand LSB and USB
offsets.  ALSO PLEASE NOTE that these frequncies assume an audio modulation
center frequency of 1700 Hz.  The AEA-PK232 uses tones centered at 2210 Hz and
some others may use tones centered at 2125 Hz.  Radios connected to a PK-232
need to be tuned 510 Hz higher using LSB and 510 Hz lower on USB.  The other
TNC's which use 2125 need an offset of 425 Hz.  The following describes
several notes about HF APRS operation.

     When you tell APRS that you are operating HF instead of VHF, it multiplies
all timing routines by four to make up in the difference between 1200 and 300
baud.  So the net cycle time on HF is four times slower.  One other thing it
does is to change your default ALIAS from the generic callsign of RELAY to the
generic callsign of ECHO.  Read the info on the ctrl-V command and in the
README.RPT file to fully understand the implications of the generic ALIAS of
RELAY used by all VHF APRS stations.  Obviously, for a nationwide HF net, we
do not want everyone digipeating everyone else's packets!  So the change to
the alias of ECHO is only important in that it REMOVES the generic ALIAS of
RELAY!  Of coure you can still digipeat your HF packets off of another station
but now you should specify exactly who, by callsign, NOT by the generic call
of ECHO.  (Except in real emergencies where you want to maximize the chance
of your signal being heard at the expense of nationwide collisions!)

GATEWAYS:  APRS has great applications through HF/VHF gateways.  By assigning
the generic APRS alias of GATE to the gateway function in any of the dual port
Kantronics or AEA TNC's, then any HF station can gateway in your local net and
any station in your VHF net that wants to be seen nationally on HF need only
specify the unproto path of GATE.  HF stations can probably use the VIA path
of GATE most of the time, because the slow HF operation could hardly clutter
up any local VHF APRS networks.  But users on VHF APRS networks should never
use GATE on the VHF side of their gateways except under extreme caution.  This
is of course because there will probably be more VHF users in a single VHF net
than there will be HF users across the whole country.  So the HF net would be
totally clogged.  I am concerned about over-using the VHF side of the gateway,
and have included a mechanism to discourage the use of the GATE via path on
VHF.  That way a user will have to intentionally specify the GATE function
each time he wants to use it and there will be no way for him to forget about
it and accidently contribute to un-necessary QRM!

TYPICAL DUAL PORT GATEWAY SET UP:  So here in Annapolis, I have the two KAMS
each with an HF radio on the two HF frequencies.  The audio of their VHF
sides are tied together into a 1 watt radio on 145.79.  Both KAMS run with
the GATEWAY callsign of GATE so that any HF APRS packets using the VIA path
of GATE will be seen on our local 145.79 APRS net.  Similarly, any VHF station
on our local 145.79 frequency that uses the path of ...,GATE will go out on
HF.  The purpose of this gateway is to support the big picture APRS objective
of allowing any mobile station anywhere in the country to report his position
back to his home QTH.  If I am driving through ANY area in the country that
is using 145.79 for APRS and that has a GATEway station on either of the two
APRS HF frequencies, my 2 meter APRS position report has a good chance of
making it all the way back to my PC display.  All I have to do is to set my
mobile TNC outgoing path to WIDE,GATE,GATE,W3XYZ.  This way the closest generic
APRS WIDE digipeater will digipeate my report to the nearest GATEway. It will
in turn digipeate the report out onto the HF APRS net.  My Annapolis HF GATE-
way will then see the second GATE and repeat the packet onto the local VHF
net through the local W3XYZ digipeater, which will then reach my home.  Notice
that all of the other gateways will also transmit the packet, but only the
Annapolis packet will get digipeated via the W3XYZ digipeater.  For this
reason, an APRS gateway should have a low power VHF radio only capable of
hitting the nearest VHF APRS digi so that it does not QRM a large area.
Neat huh!

CAUTIONS:  Obviously the shared HF APRS net cannot handle a lot of such cross
band position reporting, but if you are far enough away to have to use an
HF link to report your position, then nobody really cares exactly where you
are minute by minute, simply which town you are in is fine.  So mobile stations
using this gateway function should probably not beacon any more often than
once every half hour.  Similarly, HF stations such as boats and RV's I would
not expect to routinely report any more often than that either.  We will just
have to see how APRS grows.

OTHER BANDS:  I only have two HF radios, which is why I have not looked for
other APRS packet frequencies on the other bands.  I would avoid the QRM on 20
meters and would look next on the 18 MHz band for a good permanent APRS report-
ing frequency for the long haul round-the-world boaters.  Of course, an APRS
frequency on the 20 meter band would be fun for just working APRS HF DX and
seeing where those foreign stations are!  As of version 2.05, APRS can also
plot stations using only grid squares.  Any BEACON packet with the grid sq
enclosed in brackets at the beginning of the BText will be plotted.

README.NEW                NEW stuff WHICH MIGHT CONFUSE OLD USERS

I Made a lot of minor changes in 2.08 that may confuse the veteran user of
APRS who is used to certain Key strokes.  Always read the HELP screens and the
INFO screen closely for any changes.  Here are some highlights...

FEATURES - Map Features such as Roads, Lines, Labels, CIties, Water, etc have
       lost their unique ALT keys and are now toggled on/off via the FEATURES
       (alt-F) key.  This freed up keys for other new or moved functions:

       alt-P   POSITION FILTER  (was alt-F) turns on/off the position filter
               (does not save positions to disk that move less than 80 yards)
       alt-C   Turns on and off the CW sending of new BEACONS and MSGS
       alt-W   WEATHER command.  Cycles through all WX reporting stations
       alt-L   LOAD from BACKUP.BK  Permits one key reload of backup file
       ctrl-W  Sends out an ?WX? to query all WEATHER STATIONS.

CONTROL PANEL - With the changes above, I can now use only control keys for all
       CONTROL panel functions to be more consistent with the name.

       ctrl-G  Now toggles on/off the logging function (instead of alt-G)
       ctrl-O  Now toggles on/off the ONLY BEACONS or OTHER PACKETS
       alt-R   Now is the REPLAY function (vice ctrl-R)
       alt-Z   Now is the Zero Memory cmd (vice ctrl-Z)
*      alt-C   Now you must use ALT-C to Save or Alter your CONFIG file

HOOKED STATIONS ON P and L SCREENS - All keys have changed, and the Alarm
       function was added to the P list.  Use the first letter of the command.

ALARM POSIT - Allows you to mark a station for ALARM.  If the station moves
       outside of the FILTER (alt-P) range, then an alarm sounds.  The BEEPS
       are cleared by UNHOOKING the station, but the ALARM remains set for
       any more movement.  To disable the alarm, toggle it off on the P screen.

REPLAY - Significant improvements permit turning on/off CALLS and Zooming in
       and out as well as re-centering during replay!

THENETs - APRS now recognizes the fixed station position report format anywhere
       in a BText.  This was necessary for THENET Nodes which do not permit the
       SYSOP to change the first few fields of BText which are hard coded to be
       the NODE name and software version number.  When the SYSOP uploads a new
       BText to the node, it is only appended to the end of this fixed string
       data.  Now, APRS will look further into any BText to find the !LAT/LONG/
       SO TALK TO YOUR NODE-OPS and GET THEM TO ADD POSITIONS IN APRS FORMAT!

WEATHER - With version 2.07 there is an automatic weather station option that
       inserts wx conditions into your Posit.  All wx stations, whether manual
       or automatic, can be selected with the alt-W key.  The last selected wx
       station will show its wx conditions in a box at the top of the screen.
       Whenever a new report comes in from that station, the box will be up-
       dated.  This makes it possible to "lock on" to a neighbor wx station,
       and have those conditions always displayed on your screen.  For more
       info on the weather capabilities of APRS, see the README.WX file.

GPS/LORAN INTERFACE - After version 2.0, APRS includes an optional automatic
       interface to any NMEA-0183 GPS/LORAN device via the serial COM port.
       With this optional interface, you can carry APRS with you on a LAPtop
       and see where you are going, James Bond style. See README.GPS for more.

                           APRS HELP!

     Since my on line HELP screens seem to only make sense to expert users, its
time to further elaborate on the key commands for APRS.  ALSO NOTE THAT MANY
COMMAND CHARACTERS HAVE CHANGED BEGINNING WITH VERSION 2.08!  First, there are
seven major APRS screens listed below.  In almost all cases, all APRS commands
are active from all pages.  The first Help page defines all command characters.

   MAP       - For showing the positions of all stations and objects
   LATEST    - Shows the latest Beacon or broadcast message for all stations
   POSITIONS - Shows position packets and comments from all stations and Objs
   WHEN HEARD- Shows station activity in number of packets per hour per station
   ALL BCNS  - Chronological log of all beacons and messages
   HELP      - Toggles between two screens
   INFO      - Information (further help and suggestions)


MAP DISPLAY:  The map display is the most important display in APRS.  It shows
a map of the packet network area and the positions of all reporting stations.
Stations reporting packet positions over the air are shown in white, objects
that you are reporting to the network (uplinking) are shown in yellow, objects
reported by other stations are shown in purple, positions that have not been
updated in 2 hours are shown in gray.  To help highlight the WIDE area
digipeaters in an APRS net, the WIDE digipeaters are shown in green.

  SPACE   - Displays the current map

  ARROWS  - Move the map cursor on the sscreen.  If you turn NumLok off then
            hold the shift key with the white arrow keys, then cursor will
            move 5 times faster.

  PgUp/Dn - Zooms the display in and out by a factor of 2.  Ctrl-PgUp/Dn
            zooms by a factor of 8.

  Home    - Will home the center of the screen to the current cursor location

  End     - Will return the map to the default position stored in CONFIG file

  D       - Dissables Dead Reckoning to see the last fix on a moving object

  J       - JUST ONE - Used to display just one symbol type at a time.  Used
            to selectively display

  R       - RANGE RINGS - Displays one ring at the current range scale and
            another at half the range.

  HOOK    - Hook is a Navy term for selecting an object on a radar screen. Use
            the RETURN/ENTER key to hook an object at the cursor location.  To
            progressively hook one object after another, use the gray +/- keys.
            The POSITION and BEACON packets from a hooked station are displayed
            on the bottom of the screen.  While a station is hooked, it can be
            moved by moving the cursor to the new location and hitting the
            INSert key or it can be removed using the DELETE key.  To prevent
            inadvertant movement of objects, the U key UNHOOKS an object.

  INSERT  - Relocates a HOOKED object on the screen.

  DELETE  - Deletes a HOOKED objecct on the screen

  alt-M   - MAP BOUNDARIES - Shows boarders of all MAPS in the MAPLIST.map file

  alt-F   - FEATURES:  Toggles a number of map features on/off.  There used
            to be separate alt keys for each feature, but in version 2.08,
            these were all consolidated into the FEATURES submenu.  Features
            are Boundaries, Headings, Roads, Calls, Waterways, etc.


DISPLAY SCREENS:  The remaining six APRS display pages are called up with
single key commands as shown below.  If there are more than one page of packet
stations in the net, then use the PgUp and PgDn keys to cycle through multiple
pages.  On both the P and L lists, you can move the cursor to select a single
station.  A prompt then allows you to (1) display the object on the screen, (2)
see a chronological list of all previous beacons from that station, (3) delete
the entry, (4) insert a position for a BEACON only station, etc.

  L - LATEST DISPLAY - Lists the latest BEACON packet from all stations.  This
      screen is like a braodcast message display showing the latest bulletin
      from each station.  It is an active screen updated in realtime as packets
      come in.

      F - FULL LENGTH - Same as L but displays full length of long beacons

      O - ORDER THE LATEST LIST - Moves older beacons to the start of the list,
          and the most recent beacons to the end.  ALT-P does the same thing,
          but also deletes all stations more than a day old.

  P - POSITIONS DISPLAY - Lists the latest POSITION packet received from each
      station.  Since each position report can contain comments, this display
      is useful for seeing comments and resolving position data.

  W - WHEN HEARD - This display shows statistics of the number of packets heard
      from each station for the last 24 hours.  It is useful for observing
      station activity and on HF for observing propogation changes.

  A - ALL PACKETS - This display shows a chronological history of all packets
      received.  It also includes your incomming and outgoing message lines.
      Since messages do not have a time of receipt appended to them, this
      display is useful for seeing approximately when a message line was
      received.

  H - HELP - Toggles through two different pages of HELP

  I - INFORMATION - Another screen of useful information

  N - NON STANDARD TNC's - Gives info on operation with non TAPR2 TNC's.


TEXT MESSAGES:  There are two types of messages in APRS.  First are broadcast
messages (beacons) to all stations.   New BEACONS are shown at the bottom of
all APRS screens on frequency and highlighted in green so that all stations see
the new message or change in status.  They are also added to the ALL and LATEST
pages of all stations on frequency.  These beacons are perfect for alerting the
net to your current status.  Secondly, APRS implements a one line message
capability between operators.  Each line is ACKed when received by the other
station.  Multiple lines can be buffered up for eventual delivery.

  B - Displays your latest Beacon message.   Alt-B - Alters it.

  M - Disaplays messages on the current screen.  When ever you call up a new
      APRS screen, the messages are overwritten.  They will reappear if there
      is any change, such as an incomming message line or an ACK to one of
      your outgoing lines.  If messages are already displayed, then the M key
      forces an immediate repeat transmission of the last undelivered line.

  S - SEND MESSAGE - You are then prompted for the callsign of the station
      that you want the message to go to.  If you already have outgoing
      message lines pending, then the previous station callsign is pre-loaded.
      If you don't want to send the message, just enter a blank line.

      NOTE: APRS messages are the least efficient APRS mechanisim.  Intense
      real-time rag-chews on a busy APRS frequency should be avoided or at
      least should use the TNC talk mode via a normal AX.25 connection.

  K - KILL incomming message lines.  K key kills one line at a time.

  E - ERASE outgoing lines.  E key erases one outgoing line at a time.  First
      it erases *ACKed* messages, and then erases other lines.

 ^C - CW MESSAGES - Toggles CW mode on and off so that new incomming message
      lines to your station are sounded out in CW if you are not near your CRT.

 ^T - TALK TO TNC - This commmand allows you to disable APRS and talk straight
      through to your TNC to establish a direct CONNECTION.  This is useful for
      connecting to another APRS station's internal TNC mailbox to leave a
      message if he is not on line with APRS or for a quick keyboard to
      keyboard QSO with another APRS operator, known to be at his keyboard.
      These brief keyboard connections are not too dissruptive to other APRS
      operations on frequency as long as no computer data is transferred.

OBJECT FUNCTIONS:  Any station may place an object on the map to be displayed
at all stations.  Once on the screen, the object is listed in the P-list with
a (+) symbol.  This means it will be transmitted by your station.  You can STOP
transmitting each object by hooking it on the P-list and hitting S.  Users with
an un-validated copy of APRS are limited to only one uplinked object.

  alt-A - ADD AN OBJECT - WIll add a new object to the screen at the current
          cursor location.  You are prompted for all pertinent information.
          There are 28 symbols that can be used to display the object.  They
          are listed alphabetically.  Some symbols are specific and some are
          generic so that they can be defined for each special APRS net.

  alt-D - DIRECT L/L INPUT - This command allows you to add an object to the
          screen without having to slew the cursor to the desired location
          first.  It is useful when you are given the L/L of the object, such
          as for entering the position of reported hurricanes.

  ^U    - UPLINK ON/OFF - Disables uplinking of all of your objects.


OPERATIONS FUNCTIONS and CONTROLS:

   C    - CONTROLS - Displays a control line at the bottom of the screen
          showing the status of many APRS switches and modes.

  ^X    - XMT ENABLE - Toggeles on/off

  ^U    - UPLINK ENABLE - Toggles on/off.  If on, then your objects marked
          for uplinking, will be uplinked to all stations in the net.

  ^O    - OTHER PACKETS - Use this command to toggle the APRS beacon processing
          filter between APRS Only packets or ALL OTHER packets.  The state
          of this switch in shown on the control line.  Use OTHER to monitor
          non APRS frequencies to collect BEACONS and see who is on the air.

  ^Q    - QUERY -  This command sends an immediate APRS query packet to all
          stations on frequency.  All APRS stations will respond with all of
          their BEACONS, POSITS, OBJECTS, and MESSAGES sometime in the next
          minute.  This command is AUTOMATICALLY sent whenever a station starts
          up the  APRS program.  This is why you hear a flurry of packet
          activity each time a new APRS station fires up on frequency.  With
          version 2.05, you can selectively Query any single APRS station by
          sending him a one-line message with the characters ?APRS in it.

  ^W    - WEATHER QUERY - Same as QUERY, but only weather stations respond.

  ^P    - PING -  Sends out a ping packet.  If the packet is digipeated by your
          selected VIA path, you will see it monitored on the bottom line of
          your display.  This lets you know that your station is transmitting
          and that the digipeater in your selected VIA path is good.

  ^V    - VIA PATH - Used to set up your outgoing digipeater path. (IMPORTANT!)
          If you have not selected a digipeater that covers your APRS net, then
          your packets and acks will never get to the other stations on freq
          even though you see them fine.

  ^G    - LOG on/off - After 200 position reports are logged on moving stations
          then the positions are saved to a track history file for later replay.
          This command allows you to turn off that function.

CONTROL FUNCTIONS:  These commands are set up and control functions that are
not done that often in normal operation:

   V - VALIDATE - This key is used to bring up the information on registering
       your copy of the program and for entering your validation number.

altC - CONFIGURATION FILE - Used to save your current configuration.  Saves
       the current map size and location as well as the state of HF/VHF, and
       your digipeater path.  Only registered users can save a config file.

  ^L - LOAD - This key allows you to load a backup file.  The file named BACKUP
       is saved every time you quit APRS so that you can restart the program
       to the last on air situation.  I save a different file for each packet
       frequency so that my map only shows stations on the current frequency.
       To facilitate this process, you only need to enter the numeric digits
       to LOAD a backup FREQxxxx or HFxxxx file.

  ^S - SAVE - Used to save the current situation in a file.  The file name
       defaults to the name of the last file loaded.  It is a good idea to
       save a separate file for each packet frequency on which you operate.

  ^I - INITIALIZE TNC - sends out TNC commands to setup the TNC for APRS

  ^X - XMT ON/OFF - disables routine transmitting from your station.


TRACK HISTORIES - All position reports are saved to memory and eventually to
file for subsequent replay.  Several commands are used:

 altR - REPLAY - Used to replay track histories for moving stations or objects.
        Track histories are retained in memory for instant replay up to 200
        points.  After that, a file is automatically saved and memory cleared
        for further points.  If less than 200 points are in memory, you must
        manually forece a save using ^S before exiting the program or the
        track history points in memory will be lost.  During Replay several
        commands are useful to center the screen on the moving object, change
        the speed of replay and zoom in or out, etc.

  ^G    LOG - Toggles on and off the automatic logging of track histories to
        file.  Default is ON so that after 200 position reports, a file is
        automatically saved and memory is cleard for further accumulation.  If
        off, the 200 reports are retained in memory only.

alt-P  POSITION FILTER ON/OFF -  All position reports are compared with the
       last report from the same station.  If the position is the same, then
       the report is not saved in memory or to a track history file.  If this
       POSITION filter, which is normally on, expands this comparison out to
       80 yards to include most of the randomness added to the GPS system by
       the Deaprtment of Defense.  This prevents non-moving GPS packet stations
       from filling up track history files with redundant positions.

DIRECTION FINDING:  APRS can instantly traingulate fixes from multiple reporting
packet stations.  Even stations reporting a beam haeding that are not APRS
equipped, can be placed on the map by any APRS station and be given a beam
heading.  APRS assumes that any station or object with a COURSE given but with
a speed of zero is a DF station with the COURSE representing the beam heading:

   ^B - BEAM HEADING - for enteringa beam heading for your station

    X - CROSS TRIANGULATE A FIX - plots all beam headings on the map