[Xastir] GPS NMEA sentences decoded by Xastir

[Fred Hillhouse]

The assumption with most APRS software is there will only be a GP talker
connected outputting only GP types. Other NMEA talkers have always been
around but only one is supported.  Now with alternate constellations
(GLONASS and BD) maybe is time to include other talker types? At least it is
something to consider at some point.

Aside from the previous three, on a sailboat there may be instrumentation
that uses II (integrated instruments). Maybe Raytheon (WAG)? Giuseppe is
using a NMEA system that outputs II types. I suspect this may be typical of
nautical systems but I do not know.

This is just one second from my receiver:
14:09:46
$GPGGA,140946.0,4229.103717,N,07116.334517,W,1,04,1.1,92.2,M,-33.0,M,,*58
14:09:46
$GNGNS,140946.0,4229.103717,N,07116.334517,W,AA,08,1.1,92.2,-33.0,,*60
14:09:46  $GPVTG,248.4,T,248.4,M,0.0,N,0.0,K,A*23
14:09:46  $GPGSA,A,2,01,09,11,28,,,,,,,,,1.4,1.1,0.9*3D
14:09:46  $GNGSA,A,2,01,09,11,28,,,,,,,,,1.4,1.1,0.9*23
14:09:46  $GNGSA,A,2,75,83,84,85,,,,,,,,,1.4,1.1,0.9*29
14:09:46  $BDGSA,A,2,,,,,,,,,,,,,1.4,1.1,0.9*2E
14:09:46
$GPRMC,140946.0,A,4229.103717,N,07116.334517,W,0.0,248.4,210717,0.0,E,A*19
14:09:46
$GPGSV,4,1,13,01,22,164,22,07,73,258,17,08,68,046,16,09,13,217,28*70
14:09:46  $GPGSV,4,2,13,11,47,171,40,28,21,285,23,46,,,31,51,,,34*79
14:09:46  $GPGSV,4,3,13,13,01,333,,16,12,088,,23,,,,27,31,049,*43
14:09:46  $GPGSV,4,4,13,30,41,306,*48
14:09:46  $GLGSV,3,1,10,74,61,338,15,,,,32,73,49,113,20,75,11,316,18*58
14:09:46
$GLGSV,3,2,10,65,02,302,14,84,71,185,26,83,45,036,22,85,17,205,30*62
14:09:46  $GLGSV,3,3,10,66,02,354,,80,03,129,*65

Best regards,
Fred N7FMH


-----Original Message-----
From: Xastir [mailto:xastir-bounces at lists.xastir.org] On Behalf Of Jason
KG4WSV
Sent: Friday, July 21, 2017 9:53 AM
To: Xastir - APRS client software discussion
Subject: Re: [Xastir] GPS NMEA sentences decoded by Xastir

On Thu, Jul 20, 2017 at 11:33 PM, Menga <giuseppe.menga at polito.it> wrote:
> I noted in the file gps.c of the Xastir sources two problems in the 
> decoding of GPS NMEA sentences: only two types of sentences are 
> decoded $GPRMC and $GPGGA,

Those two sentences are part of the standard, they are provided by
practically all consumer devices, and they are sufficient to provide xastir
with position, course, speed, and other data needed for an APRS location
packet.

> no checksum is tested.

that's maybe a bit sub-optimal, but for most installations of xastir it
would be vanishingly rare for an error detectable by a checksum to occur.

> GPS devices have many different preambles, just in my case $IIRMC and 
> $IIGGA, II stands for integrated instruments, but there are many 
> others that are banned from Xastir.

They aren't "banned", they simply are not supported.

What sort of device is providing II sentences and, I assume from your
question, does not provide GP sentences?

Have you experienced errors that would have been detected by checksum
verification?

-Jason
kg4wsv
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