Ham Radio 2000/Ham Radio 2000.iso/ham2000/packet/aprs75c/aprs.txt

Text File | 1996-04-10 | 18KB | 313 lines

APRS.doc 7.5b    AUTOMATIC PACKET/POSITION REPORTING SYSTEM (APRS)


     APRS is the result of my experience over the last 18 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
simple message traffic from point to point.  It has been difficult to apply
packet to real time events where information has a very short life time.

     APRS, however, provides universal connectivity to all stations but
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???  To answer these questions, APRS is a full featured
automatic vehicle location and status reporting system too.  It can be
used over any 2-way radio system including HAM, CB, Marine Band, and
Cellular Phone.  See CB.txt and CELLULAR.txt.

     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.

ACARS: If your TNC has an ACARS modem for receiving Airline digital packets
on 131.55 MHz, then the optional APRSair.EXE will plot the positions of all
aircraft in range (usually up to about 200 miles out)..  See ACARS.txt

USING APRS ON ALL DIGITAL CHANNELS:  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 an excellent application for using orbiting
packet digipeaters such as on the Shuttle, AO-16, WO-18, LU-19, MIR, and
AO-27.  APRS only requires one successful packet for everyone to see each
successful station.  The typical *CONNECTED* ROBOT mode of SAREX requires,
a total of 5 successful packets.  Not only does APRS reduce channel loading,
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.  See SPACE.txt.

FOX HUNTING OR DIRECTION FINDING:  APRS is an excellent tool for plotting
the location of a hidden transmitter, balloon, or interfering signal.
APRS has several powerful DF tools:

  1) Plots the positions and Bearing lines of all participating stations
     whether mobile or fixed
  2) Plots the overlaping signal strength contrours for OMNI-DF reports.
     This techinque even plots big BLACK circles for NULL reports so
     that you see all the areas where the FOX is NOT!  This OMNI technique
     is very powerful and locate a jammer to a neighborhood with NO
     beams or special equipment.
  3) Fade-Circle Search and Rescue technique for single station signal
     strength location using only a OMNI antenna
  4) Optional automatic DF interface to Doppler DF units for automatic
     plotting of DF bearings.

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
to do this automatically.  All weather stations show up as a blue circle,
with a line indicating wind speed and direction.  The NEXT command in APRS
will successively highlight each WX station in turn, for WX at a glance.
APRS also has a database of the locations of most NWS sites and can crunch
a file of NWS hourly WX conditions for display.  Finally, APRS users can
set WX alarms and be alerted when WX conditions exceed those values.
See WX.txt.

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.  See DX.txt.

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.  The frequency coordinating
body can make available APRS backup files (or .HST files) showing the
psoitions of all coordinated services, both packet AND VOICE.  These files
can be distributed on BBS's to all HAMS in the area.  Loading these files
into APRS displays the established frequency users in a geographical
setting.  Also the APRS MAPS-PLOTS-POWER command can plot range contours
based on antenna height and gain, for displaying the topology of any
network and also the interference ranges of voice repeaters...


PROTOCOL - Although APRS redundantly transmits data, a fundamental precept
is that old data is less important than new data.  All APRS packets are
repeated at an ever increasing beacon period.  Each new packet is
transmitted immediately, then 20 seconds later.  After every transmission,
the period is doubled.  After fifteen minutes only six packets have been
transmitted.  From then on the rate remains at 15 minutes.  All trans-
missions can be toggled off using the CONTROLS-XMT command.  But a transmis-
sion can be forced at any time by hitting the X key.  See PROTOCOL.txt

COMMANDS:   The keyboard is always active.  Almost every key does something
or brings up additional menus.  (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 yellow).  Commands fall into 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 APRS looks in our area, FILES-LOAD the file
named FREQ-145.79.  To see the tracking of the GPS equiped Army/Navy game
football run, FILES-LOAD FBALL.BK and do a FILES-REPLAY of the file named
FBALL93.HST.  To see the Marine Corps marathon, 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:

     ALL BEACONS - Displays a list of all beacons from that station.
     MOVE        - Move the station by moving the cursor
     DELETE      - Delete the station.
     FOLLOW      - Force this object to FOLLOW a course (APRSdr only)
     UPLINK      - Toggle on/off transmiting the object to others
     KILL        - kill the object from all displays in the network
     ALARM       - Sets an alarm if that station ever moves.
     TRACK       - Always center display on selected station as it moves
     MARK        - Mark stations for selective display with the JUST command

The hook function also works on the LATEST and POSITION display lists by
using the up/down arrow keys.

REPLAY:  Replay past track histories 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 following 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, MAPLISTS and README.  There are several
        other files used by the system:

  MAPLIST.USA  - The file that lists all map files to be used by APRS.
                 In version 74a, these were all moved to the MAPLISTS
                 directory.  Change to different MAPLISTS using the
                 MAPS-CHANGE command.
  BACKUP  .BK  - Automatic backup of system every time program is quit.  It
                 can be loaded quickly using the FILES-LOAD-B command.
                 Or Automatically by invoking APRSXX/B at the DOS prompt.
  MAPFIXxx.EXE - A powerful program for fixing, drawing, and modifying 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.

APRSdr.EXE:  For tracking known OBJECTS that move at KNOWN speeds over
a KNOWN course, such as the runners in a Marathon, use APRSdr.  This
program will Dead Reckon objects along the course, so that you can
reasonably track the progress of the event, without having to strap
a GPS/TNC and RADIO to the head of the lead runner.  All GPS mobiles
will also be tracked.  This is a trememdous visual aid for NET CONTROL.