Nmea GGA sentence always 12 SV ?

Q&A forumCategory: QuestionsNmea GGA sentence always 12 SV ?
amorosik asked 2 weeks ago

Why we see alway 12 SV on gga Nmea sentence (field n.7) ?
Also with 30-32 satellite signal (gps, glonass, beidou, …)
 

clive1 replied 2 weeks ago

I’d imagine so it doesn’t break a few million apps with dependency. There is some disagreement if it reports In-Use or In-View
You should be able to sum satellites reported in the GSA sentences, but again that’s likely limited to 12 per constellation.
The preferred method is to use the UBX forms as NMEA sentences now generate an excess of data.

2 Answers

 GGA Message Structure F9P-ZED:
Time and position, together with GPS fixing related data (number of satellites in
use, and the resulting HDOP, age of differential data if in use, etc.).
$xxGGA,time,lat,NS,long,EW,quality,numSV,HDOP,alt,M,sep,M,diffAge,diffStation*cs

  •  7-numSV – numeric 08 Number of satellites used (range: 0-12)

The output of this message is dependent on the currently selected datum
(default: WGS84). The NMEA specification indicates that the GGA message is
GPS specific. However, when the receiver is configured for multi-GNSS, the
GGA message contents will be generated from the multi-GNSS solution. For
multi-GNSS use, it is recommended that the NMEA-GNS message is used
instead.
GNS Message Structure F9P-ZED:
Time and position, together with GNSS fixing related data (number of satellites
in use, and the resulting HDOP, age of differential data if in use, etc.).
$xxGNS,time,lat,NS,long,EW,posMode,numSV,HDOP,alt,altRef,diffAge,diffStation,navStatus*cs

  • 7-numSV – numeric 10 Number of satellites used (range: 0-99)

Example:
$GPGGA,092725.00,4717.11399,N,00833.91590,E,1,08,1.01,499.6,M,48.0,M,,*5B
$GPGNS,091547.00,5114.50897,N,00012.28663,W,AA,10,0.83,111.1,45.6,,,V*71

clive1 replied 2 weeks ago

+1 That would be the way to go then.