SCREEN.txt 6.5c              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 |
   |                       |-------------------------------------------|
   |-----------------------|                                           |
   | 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     |
   ---------------------------------------------------------------------
               * As of version 6.5, APRS supports highres 43 line VGA mode
                 and these lines will be 41, 42 and 43 respectively
 

   CURSOR BOX:  The cursor box displays the location of the cursor and the map
                range.  The range shown 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.

   Bearing/Range: If the 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 Square:   This field will show the Maidenhead Grid Square location of
                  the cursor when the MAPS-PLOTS-GridSquare command is given.

   NatlGridRef:   The English version of APRS displays the National Grid
                  Reference in this box

   FLAG AREA:     This area is 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
             
   TIMING/WARNING: Shows the current time, and the time to go before the next
                   Beacon, Posit, Object or Message packet to be transmitted
                   from your station.  The 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 >9 is shown.
                   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:     This line is the bottom most useable text line that will
                  not automatically scroll the screen.  Its uses:
                   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 any received BEACON that is new

   25th LINE:     This line displays monitored packets.  It displays the
                  packet first, and then over-writes a 3 character label
                  showing how APRS interpreted the packet.  Typical labels:
                    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:  A CSMA packet channel with no hidden transmitters nominally
                  achieves about a 36% throughput, considering acks and
                  retries.  For displaying channel loading, I use that 36%
                  figure as 100% channel load.  THat is why you may sometime
                  see figures approaching 300%.

   No DIGIPEAT... Since APRS is always monitoring the channel, it can tell
                  if its own packets are being digipeated on the channel.  If
                  it does not hear a digipeat of its transmitted packets, then
                  it displays a message on the 25th line.  On any packet
                  channel, packets will suffer collisions preventing some
                  packets from getting through.  If you see this message
                  on everyone of your packets, then there is something wrong
                  with your transmitter or your chosen UNPROTO path.  This
                  is turned off on HF where there should be NO digis.
               
  + PLUS 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
                  RED       - WX alarm values exceeded
                  Purple    - OBJECT reported by someone else
                  Yellow    - OBJECTS you are uplinking

