*** Automatic Packet Reporting System *** From: "Steve Davis" Date: Wed, 14 Jun 1995 19:06:31 +1200 Subject: APRS APRS is Automatic Packet Reporting System, or Automatic Position Reporting System It is designed to report positions of objects via amateur (ham) packet radio. These positions can be displayed on maps. It is distributed in a demonstration form, registration is required to enable the GPS option. It is intended for amateur radio and other non comercial use. The author of APRS for the PC is Bob Bruninga WB4APR. There is also a Mac version available. APRS is available from ftp.tapr.org in /tapr/sig/aprs/upload Usually in the form of APRSnn.ZIP Possible applications for SAR are tracking of search teams. The problems are that each team would require a GPS receiver, a packet modem, and a transmitter capable of getting a signal back to HQ. Problems arrise from the nature of the areas that SAR occurs in, and getting a lock on satellites, and getting a good signal back to HQ on a regular basis. Total size and weight are also a consideration, especially when adequate power to last for the duration of a search is considered. Another problem is that the size and definition of the maps is limited. These are not insurmountable. Here is an intro file to APRS. 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 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 INPUT-ADD command and updating their positions using the cursor and INSert keys! The full 32 pieces are already loaded and saved in CHESS.BK. To move a piece, just hook it, move the cursor to the new position and hit the INSert key. Other APRS stations will see the game progress too! You should consider going to an unused frequency so as not to clutter an active APRS net, however. Also, after a piece has been moved and the new location seen by the other player, it is useful to Quit uplinking it to minimize QRM. ---------------------------------------------------------------------- Steve Davis ZL2UCX | Internet: steve@zl2ucx.gen.nz P O Box 120 | Packet: zl2ucx@zl3ac.#80.nzl.oc Christchurch | New Zealand | Fax: +64-3-343-0461 ----------------------------------------------------------------------