[aprssig] GPS NMEA and APRS Trackers

[Andrew Rich]

Hello

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
$GPGSA - PDOP, HDOP, VDOP
$GPGGA - Time, Lat, Lon, Fix quality, Number is sats, HDOP, Altitude

Characters

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 

GARMIN GPS18w

$GPRMC,034546,A,2734.4630,S,15306.2268,E,000.0,299.7,170704,011.2,E*65
$GPGGA,034546,2734.4630,S,15306.2268,E,1,07,1.5,47.8,M,39.2,M,,*63
$GPGSA,A,3,04,05,06,,,10,17,24,30,,,,2.3,1.5,1.0*33
$GPGSV,3,1,09,04,21,138,44,05,70,225,44,06,15,250,35,07,05,092,00*72
$GPGSV,3,2,09,09,30,323,00,10,40,038,39,17,83,263,33,24,57,150,47*74
$GPGSV,3,3,09,30,32,222,44*40
$GPVTG,300,T,289,M,000.0,N,0000.0,K*7E
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