[aprssig] APRS - ALL CALL and ROLL CALL

Andrew Rich vk4tec at tech-software.net
Thu Dec 29 21:57:24 EST 2011

On thing we do in Mode S RADAR is ALL CALL and ROLL CALL.

Do you think this sort of thing has application in APRS ?

A smart digi sends a broadcast.

If a tracker is new to the digi, it acquires the target.

It then calls for a response from the tracker in a ROLL CALL ( poll )

- Andrew - 
  ----- Original Message ----- 
  From: Andrew Rich 
  To: TAPR APRS Mailing List 
  Sent: Friday, December 30, 2011 12:55 PM
  Subject: GPS NMEA and APRS Trackers


  Looking at making use of as much data as I can send over 19k2 EasyRadio modules.

  I would like to hear from the hardware guys how they handle the fact that not all NMEA strings seem the same.

  Some have fixed character lengths, and some have zero padding.

  How do you get around the fact you can't control what sort of GPS someone might hook up to a tracker ?

  How do you get by without having to specify a NMEA format that a devices complies with ?

  I have taken a GARMIN GPS18 as an example.

  Andrew VK4TEC


  $GPRMC - LAT, LON, Time, A/V , Speed , Track angle, Date, MAG VAR
  $GPGLL - LAT, LON, Time, A/V
  $GPVTG - True track, Mag track, GS Knots, GS km/h
  $GPGSV - Satellites in view
  $GPGGA - Time, Lat, Lon, Fix quality, Number is sats, HDOP, Altitude


  Lat - 1234.5678 ( -90.0000 to +90.0000 ) 
  Lon - 12345.6789 ( -180 to + 180 )
  E/W - E or W
  N/S - N or S
  Time - HHMMSS
  A/V - A or V
  Speed - 123.4 Knots
  Track Angle - 123.4 Deg
  Date - DDMMYY
  Mag VAR - 123.4 Deg 
  True Track - 123.4 Deg T
  Mag Track - 123.4 Deg M
  GS knots - 123.4 Knots
  GS km/h - 1234.5 Km/h
  Sats in view - 12
  PDOP - 1.2
  HDOP - 1.2
  VDOP - 1.2
  Altitude -  ??
  Fix quality - 1 


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