DP Tool Club 24/CD_ASCQ_24_0995.iso/vrac/aprs72a.zip/README/APRS.DOC

Text File | 1995-06-23 | 20KB | 334 lines

APRS.doc 6.8       AUTOMATIC PACKET REPORTING SYSTEM (APRS)


     APRS is the result of my experience over the last 17 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.  Since APRS is shareware
everyone is encouraged to play with it all they want and to NOT feel compelled
to register.  I want APRS, or something like it, to become a defacto standard
for packet exchange of graphical information to help us all.

     APRS avoids the complexity and limitations of a connected network.  It
permits any number of stations to exchange data just like voice users would
on a voice net.  Any station that has information to contribute simply sends
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?  Whats the Weather at various points in the County?  Where are the
power lines down?  Where is the head of the parade?  Where are the VIP's?
Where is the mobile ATV camera?  Where is the hurricane?  WHERE IS THE DX???

     Included on the distribution disk are several README text files on
applications of APRS such as for weather nets, direction finding, plotting
satellite contacts, and monitoring DX clusters.  You must read at least the
README.1st, DEMOS.txt, NewNotes.txt and HELP.txt files.  APRS uses 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.
In DX cluster mode, it accumulates a list of all users and what was their
latest command to the cluster.

     POSITIONS - This display maintains a separate list of the positions of
each station often including a brief comment.  These posits show the latest
time of receipt and give an indication of the latency in the network over
unreliable paths such as HF.  They can also contain DF and or WX info.  In DX
mode, this list contains the posits of all DX spots and user-locations heard.

     MAPS - Maps from .5 miles up to 2000 miles can be displayed. Stations
that are transmitting a properly formatted position beacon will be plotted.
Stations reporting a course and speed are dead-reckoned to their present
position.  A database of most National Weather Service stations is built in.
You can zoom in to any point on the globe!

     MESSAGES -  In addition to the BEACON text one-line broadcasts, there is
an operator-to-operator message capability.  Any station can send one line
messages to any other station.  On receipt, the messages are acked and
displayed on the bottom of the receiving stations screen until the operator
hits the K key to kill them.

     BULLETINS - This screen maintains a list of active all-net BULLETINS.
BULLETINS allow one station to send multiple lines to the BULLETIN page at
ALL stations.

     TRAFFIC - This screen shows the last 23 lines of messages exchanged
by any stations on the net.  Is useful for "READING THE MAIL".  DX mode
TALK traffic also shows up here.

     ALL PACKET 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.  In DX mode, this screen shows a
chronological list of all DX/WX/WWV and ANNOUNCEMENTS heard.

     HEARD LOG - 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.

     DIGIPEATER LIST - This display displays the raw packet header so that
APRS users can see what digipeater paths are being used by other stations.
The proper use of digipeaters is important in an APRS network.  An asterix
in the first column means that you hear the other station direct without a
digipeater!  Change your UNPROTO path to NONE to chat with those stations.
In DX mode, this list accumulates a list of all DX cluster messages
monitored.

STATION TRACKING.  Although APRS automatically tracks mobile packet stations
interfaced to GPS or LORAN navigation, it also tracks perfectly well with
manual reports or GridSquares.  APRS will use a GridSquare in brackets at the
beginning of a BText.  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.  There is also
a Tracking command on the P display that will cause APRS to keep the map
display always centered on a selected object.

GRID SQUARES:  Because of the ambiguity of a grid-square position report, APRS
will not display a four 4 or 6 digit gridsquare report on map ranges less than
128 and 8 miles respectively.  Stations reported in the same grid square are
randomly offset to avoid cluttering of callsigns on top of each other in the
same grid square.  The P-list is annotated to indicate that the position is
approximate.  It is also very brief; six characters vice seventeen.  In GRID-
SQUARE mode, APRS will send your posit via GRID SQUARE format vice LAT/LONG.
Shortening the packet is an advantage when reporting via MIR, SAREX, or HF.

USING DUMB TERMINALS IN AN APRS NETWORK:  Even dumb terminal stations can
report their positions by taking coordinates off of a paper map and entering
their LAT/LONG into their beacon text.  Using the same map, he can plot the
location of other APRS stations as he sees monitors their posits.  If all
packet stations on all frequencies would include LAT/LONG or Grid Square in
their BTexts, APRS can be used as a general purpose network topology display
on ANY packet frequency! See the PROTOCOL.txt for details on APRS formats and
see FRQCOORD.txt for suggestions for using APRS as a freq-coord display tool.

SPACE APPLICATIONS:  APRS is a solution to the effective use of orbiting
packet digipeaters such as on the Shuttle, MIR, and AO-21.  The problem with
space packet is the saturation on the uplink which makes the use of a normal
CONNECTED protocol impractical.  A CONNECTED contact requires, a total of 5
successive and successful packets.  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 everyone simply inserted 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.  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 SPACE.txt for further details.

FOX HUNTING OR DIRECTION FINDING:  APRS is an excellent tool for plotting the
location of a hidden transmitter, balloon, or interfering signal.  APRS will
display the intersection of bearing lines from a number of reporting stations
and also overlapping signal strength contours if only signal strengths are
reported.  Finally, APRS includes the Fade-Circle Search and Rescue technique
which can be used by a mobile with only an OMNI antenna to locate a hidden
transmitter.

    To use APRS for DFing, each station having a bearing report or a
signal strength  on the target, simply enters that bearing using the OPS-DF
command.  His station will then not only report his location, but also a line
of bearing or signal strength contour.  All stations running APRS will see
any reported DF bearing lines on their maps.  Further, they can track any
DF vehicles using GPS or LORAN device on board.  There is an optional  Dopler
DF registration for direct connection to a Roanoke or Doppler Systems DF unit
for automatically plotting and transmitting instantaneous DF bearings.
Please note that APRS uses 360 degrees for North and 0 to indicate a signal
strength report.  For more DF info, see the DF.txt file.

WEATHER STATION REPORTING:  APRS position reports can also include the wind
speed and direction, as well as other important weather conditions.  APRS
supports a serial interface option to the ULTIMETER-II home weather station.
With this interface, your station includes WX conditions in your position
report for display at all other stations in the network.  All weather stations
show up as a bright blue circle, with a line indicating wind speed and
direction.  The NEXT command in APRS will successively highlight each WX
station in turn, so that all WX reports can be had at a glance.  See WX.txt
for more information.  APRS also has a database of the locations of most NWS
sites for instant display.  APRS can also crunch a file of NWS hourly WX
conditions and update all NWS stations on the map.  Finally, APRS users can
set WX alarms and be alerted when WX conditions exceed those values.

DX CLUSTERS:  The positional display and real-time user communications makes
APRS an ideal tool for the DX cluster user.  Not only does he get to see all
DX spots on the map, but by operating in the monitor only mode, he has reduced
the overall packet load on the DX cluster.  This is a benefit to everyone on
the channel.  Also the APRS monitroing station will see the SPOT as soon as
the first station gets it, rather than later on down the list.

FREQUENCY COORDINATION:  As more and more BBS's, DIGIS, and NODES begin to
include APRS position information in their routine BEACONS, APRS makes an
excellent tool for frequency coordination.  If the frequency coordinating
body makes available APRS backup files (or .HST files) showing the psoitions
of all coordinated services, both packet AND VOICE, then these files can be
distributed on BBS and by other means to all HAMS in the area.  By loading
these files, users can instantly see the established frequency users in a
geographical setting.  Add to this visual reference, the ability of APRS to
plot crude range ring contours based on antenna height and gain, and you can
see that APRS is a very useful tool for displaying the topology of any
network and also the interference ranges of voice repeaters...


PROTOCOL - Since the objective of APRS is the rapid dissemination 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 can be turned off using one of the CONTROLS commands.  But a transmis-
sion can be forced at any time by hitting the X key.  For details on the APRS raw packet
formats see the PROTOCOL.txt file.  The maximum period can be set to a period
even greater than the 15 minute default.  See the CAP section in AIRCRAFT.txt.

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.  (APRS processing of packets on the air is
continuous EXCEPT while waiting for the user response to a prompt.  These
prompts are surrounded with a blue box).  Commands fall in to 3 categories:

SCREENS:

  Space Key           - Display map and all station locations
  L - Latest beacons  - Displays the latest STATUS BEACON from each station
  P - Positions       - Displays a list of all stations reporting positions
  A - ALL packet log  - Keeps a chronological log of all beacons and messages
  B - BULLETINS       - Keeps a list of all BULLETINS heard
  R - Read Messages   - Displays the status of your in and out messages
  T - Traffic         - Displays the last 23 lines of messages between stns
  D - Digis Used      - Displays the digipeater paths being used by others
  H - Heard Log       - Displays packets per hour per station for 24 hours
  V - VIEW            - Displays all packets on a scrolling screen

SUB-MENUS:

  F1- Help            - Select from a MENU of HELP commands
  C - Controls        - Display a one line status of all control states
  F - FILES Menu      - For Loading/Saving files, or Replaying tracks
  I - Input commands  - Used to input posits, DF info or add OBJects to map
  O - OPERATIONS      - Several commands for normal operations
  M - MAP Functions   - Functions dealing with maps
  W - Weather Menu    - Displays the number of beacons per hour per station

MESSAGES:

  R - READ            - Displays your incomming and outgoing messages
  S - Send            - Sends traffic to a station
  E - Erase           - Erases outgoing traffic lines
  K - Kill            - Kills incomming traffic lines
  T - Traffic         - Displays message traffic between other stations


DEMONSTRATION FILE:  To see how the APRS system works on our frequency, use
FILES-LOAD to load the file called FREQ579.BK.  This file contains all the
local stations on 145.79 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
Marine Corps marathon event, load MARATHON.BK and replay the MARTHON.HST file.
See Details in README.1st.

HOOKING STATIONS:  The cursor can be moved to select any station on the map
using the arrow keys.  When near any station symbol, the ENTER key will
"hook" the station.  Detail information on that station will be displayed
on the bottom of the screen.  Alternatively, use the + and - keys to step
through each station one by one.  You may also use the cursor on the P or
L-list to hook a station or object.  Once hooked, several functions may be
performed:

     1.  ALL BEACONS - The A key will list all beacons from that station.

     2.  MOVE - Move the cursor to a new location and press the Insert key.
     You are then prompted to enter in a new info as needed.

     3.  DELETE - performed by hitting the D key.

     4.  UPLINK - transmit the object to all other stations on the net

     5.  QUIT - quit uplinking the object to the net.

     6.  KILL - kill the object from all displays in the network

     7.  ALARM - You will be alerted if that station ever moves.

     8.  TRACK - APRS will always center display on selected station

     9.  #MARK - Mark special stations so that only these stations will be
     shown on the map when # is used instead of SPACE BAR for drawing a map.
     If the * key is pressed, all symbols will be shown on the map, but only
     the marked symbols (#) will show callsigns.

The hook function also works on the LATEST and POSITION display lists by
using the up/down arrow keys.  If a position exists, hitting the SHOW key
will display the map screen with that station centered on the display.

REPLAY:  The positions of any moving station can be replayed either from
memory or from a file.  Tracks are kept in on-line memory until 150 have been
saved, and then are saved to a HISTORY file.  During REPLAY, use the Calls
command to toggle on and off the display of callsigns, and use the HOME and
page keys to center and zoom the map display if the mobile station moves off
the screen.  During replay, use these commands:

      C    - CALLsigns on/off
      HOME - Homes map to presently displayed station
      SPACE- Redraws the present map to remove track clutter
      F    - Faster.  Speeds up playback
      G    - Overlays the Civil Air Patrol Search and Rescue grids
      M    - Medium replay speed
      P    - Pause
      S    - Slow.  Slows down playback
      Q    - Quit playback.
      PgUp/PgDn - Zoom in and out


FILES:  All APRS files are retained in five different sub-directories of
        BAKS, LOGS, HSTS, SYSTEM and README.  There are several other files
        used by the system:

  MAPLIST.APR  - The directory of all map files.  APRS uses this file to find
                 out what map to use for a given cursor location.  Many other
                 MAPLIST.xxx files are now available.
  BACKUP  .BK  - Automatic backup of system every time program is quit.  This
                 file is overwritten every time the program is quit.  It can
                 be reloaded by simply indicating the letter B for a filename.
  MAPFIXer.BAS - The Qbasic program I use to fix, draw, and modify APRS maps!
  SYSTEM (DIR) - Contains the following required files
     IintTAPR.TNC - Setup parameters for your TNC (InitAEA.TNC for AEA)
     RESTORE.TNC  - TNC commands used to restore your TNC after quitting APRS.
     NWSDATA.DAT  - A sample file used to load National Weather Service data
     NWSPOSNS.DAT - A file of the locations of all NWS sites
     CAPGRIDS.DAT - A file of the Civil Air Patrol Sectional Aeronautical charts
     DXCALLS.DAT  - Callsign prefix-to-LAT/LONG database for DX spots
     XXXX.SYS     - Numerous brief files for APRS internal screens


CHESSBOARD:  To demonstrate the flexibility of APRS in reporting the
movement of objects in a net, there is a 2 mile chessboard in the center
of the Gulf of Mexico.  Two APRS stations can place pieces on the board
with the INPUT-ADD command or can move existing pieces using the Cursor,
HOOK and INSert commands!  An easy way to begin a game, is to load the
CHESS.BK file which already has all 32 pieces saved.  By selecting the
alt-SETUP-OTHER-GAME command APRS not only keeps track of the move numbers
but also changes the packet address from APRS to GAME, so that others on
frequency will not see their PLists cluttered with the pieces as they are
moved. Also, GAME mode only UPLINKS the LATEST move, to minimize QRM.
You may consider going to an unused frequency so as not to clutter an
active APRS net, however.

    If you want to Kibitz a game in progress, also load the CHESS.BK file
and use the CONTROLS-FILTERS-OTHER command so that your APRS will monitor
OTHER packets on the channel so you will see the GAME packets.  If you
missed the beginning of the game, ask one of the players to use his P
list to HOOK and UPLINK any piece locations you missed.