The APRS Map Screen

This file was written to describe some of the subtleties of the APRS main map screen. There are several distinct areas where information appears. They can be grouped as follows:

   | CURSOR  BOX           |      FLAG AREA      | TIMING/WARNING AREA |
   |                       +---------------------+---------------------|
   |-----------------------+                     | MODES AREA          |
   | Brg/Rng & Grid Square |                     +---------------------|
   |-----------------------+         +                                 |
   |                                                     +             |
   |                                                                   |
   | TO CALL : Outgoing message lines  (use ERASE to delete them)      |
   | FM CALL : Incomming message lines  (use KILL to delete them)      |
   | 23rd line *                      | Heard                          |
   | 24th line *                                                       |
   | 25th line *                               | Channel load, etc     |
* APRS supports highres 43 line VGA mode and these lines will be 41, 42 and 43 respectively

Displays the location of the cursor and map range. The range is roughly the Nautical mile radius from the center of the screen to the top of the screen. Toggle range in Kilometers with the CONTROLS-KM command.

If MAPS-PLOTS-RANGE command is given, then the RANGE and BEARING of the cursor from the center of the screen will be shown in STATUTE miles. The outer concentric circle is equal to the indicated map range scale in STATUTE miles. The Bearing is shown as the GREAT-CIRCLE bearing. To see the difference, at ranges above 1000 miles, a yellow heading marker shows the actual great circle bearing.

Grid Sq:
Shows the Maidenhead Grid Square of the cursor when MAPS-PLOTS-GridSquare command is given.

Displays the National Grid Reference in ENGLAND only.

For warnings and annoncements as follows:
  1. Shows weather reports in response to the NEXT-WX command.
  2. Announces new bulletins have been received
  3. Announces DX Cluster monitoring mode

Current time, and time to go before next Beacon, Posit, Object or Message packet is to be transmitted. Time to go is in minutes until it gets below 99 seconds, and then it shows in seconds. If the time to go is greater than 9 minutes, then '# is shown for 10-19, "# for 20-29, [apple]# for 30-39, f# for 40-49, and Ø# for 50-59. This display is only updated about once every 5 seconds. Other displays:
  1. trapped errors (file errors etc...)
  2. indicator whenever GPS or other data is being fetched
  3. The box shows purple when your XMTR is disabled.

23rd LINE:
Used for text input:
  1. All prompts that require more than one character response
  2. The bottom line of the split screen message display
  3. Displays CALLSIGN/DIGIPATH and HEARD log for HOOKED stns

24th LINE:
Captures received packets that are NEW

25th LINE:
All monitored packets. After displaying the raw packet, it then over-writes a 3 character label showing how APRS interpreted the packet:
BCN: Processed to the LATEST BEACON page
POS: Processed as a POSIT
MSG: Message
APR: Other APRS formats such as ACKS
Hrd: Neither of the above
GGA,GLL,RMC,VTG: The packet had a NMEA string in it
To? means the TO field did not match one of the following APRS,BEACON,CQ,QST,MAIL,SKYWARN,SPCL,GPS
No> Couldnt find the packet >TO field identifier
BLANK:If your packets only blink and then go blank, then there is a problem with extra linefeeds.

Channel Load:
Assuming 36% is the theoretical maximum throughput on a CSMA packet channel with no hidden transmitters, APRS uses this 36% figure as 100% channel load. THat is why you may sometime see figures approaching 300%.

APRS alerts you if it does not see a digipeat of its own packets. Due to collisions, you will occassionally see this message. If you see it all the time, then there is probably something wrong with your station or your UNPROTO path. This is turned off on HF where there should be NO digis.

+ symbols:
On maps, these mark the center of each map. If they appear yellow, then that map is visible at the present screen range. If they are white, then you must zoom down one step to see the indicated map. Remember, however, that APRS will not use a map until the ENTIRE screen will fit on the given map. That is why the + symbols are useful, by zooming in near them, you will see the more detail map at its largest practical range. To see the true extent of each map file, use the MAPS-LOCK command and then zoom back out.

Symbol Colors:
White Active APRS stations
Gray TNC on-line, but APRS is not running
Dark Gray Has not been heard in 2 hours
Green APRS WIDE area digi
Blue WX stations
Lght Blue Dead Reckoned station
Dark Blue Erased posit (replaced by a new posit)
RED WX alarm values exceeded
Purple OBJECT reported by someone else
Yellow OBJECTS you are uplinking

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Mail comments/corrections on content to Bob Bruninga and on HTML formatting to Steve Dimse