Re: [gpsd-users] Used Satellites List (NMEA GSA Message)

[Ronny Pretzsch]

On 04/01/2016 08:30 PM, Gary E. Miller wrote:
> Yo Ronny!
> 
> On Sun, 27 Mar 2016 19:09:20 +0200
> Ronny Pretzsch <address@hidden> wrote:
> 
>> I noticed that the gps clients (xgps, gpsmon) show too few satellites
>> as being "Used" in the satellite list and in SkyView. Furhermore only
>> GLONASS Satellites are indicated as being "Used".
> 
> Fixes to this problem were committed to gpsd head this week.
> 
> So either pull git headd, or wait for 3.17.

Yo Gary,

I pulled head and compiled. Problem is still there.

A glimpse on gitk shows the commit "Fix GPGSA/BDGSA processing ..."
which you seem to refer to. But this does not address the described problem.

According to Ublox documentation NMEA output for GSA is NOT like

$GPGSA...
$GLGSA...
$BDGSA...

but always GNxxx
$GNGSA... (for GPS)
$GNGSA... (for GLONASS)


Note that this is very different to the GSV message where the prefix is
never GN but always GP,GN,BD or whatever.

Examples:
$GNGSA,A,3,32,12,25,14,,,,,,,,,6.06,3.40,5.02*1C
$GNGSA,A,3,85,86,,,,,,,,,,,6.06,3.40,5.02*1F

$GPGSV,4,1,13,02,28,116,,03,01,006,,06,28,069,,12,79,039,22*70
$GPGSV,4,2,13,14,38,286,26,17,02,041,,19,26,049,,22,00,328,*72
$GPGSV,4,3,13,24,49,147,23,25,56,275,26,29,18,208,19,31,05,309,*79
$GPGSV,4,4,13,32,34,289,27*4B
$GLGSV,2,1,08,66,15,280,18,67,17,333,,74,23,113,,75,74,073,20*6B
$GLGSV,2,2,08,76,40,311,,84,35,038,,85,66,119,27,86,26,183,26*6F

I think the only way to solve this is to merge consecutive GNGSA
messages. (Although NMEA does not say it has to be consecutive).


Regard
Ronny

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