I am trying to force the EM7455 GPGSA sentence into a manual 3D fix.
I have a BU-353-S4 USB GPS that I have been using in the interim while I get the EM7455 setup. The output of the NMEA string for that device is:
$GPGSV,3,1,12,07,71,181,23,11,59,094,14,08,41,049,21,28,36,288,2870
$GPGSV,3,2,12,13,18,312,29,27,10,049,28,09,05,198,24,51,35,213,70
$GPGSV,3,3,12,31,72,291,17,53,052,25,43,295,18,41,056,71
$GPRMC,140039.000,A,4xx2.5238,N,08xx5.9687,W,0.00,0.00,190620,A7A
$GPGGA,140040.000,4xx2.5238,N,08xx5.9686,W,1,07,1.0,193.5,M,-34.0,M,000069
$GPGSA,M,3,07,11,08,28,13,27,09,1.6,1.0,1.331
As you can see, the GPGSA string shows Manual 3D fix and the GPGGA string has our current altitude available. When I use this device in our data acquisition program, it shows all 3D GPS coordinates required.
When I use the EM7455 card (!GPSNMEASENTENCE=F), I get the following strings:
$GPGSV,3,1,12,01,35,136,26,07,71,181,36,08,42,049,37,09,05,198,2278
$GPGSV,3,2,12,11,58,097,37,13,17,312,40,17,12,224,36,27,10,047,277A
$GPGSV,3,3,12,28,34,286,35,30,63,291,44,46,43,51,4074
$GPGGA,135847.0,4xx2.525468,N,08xx5.972681,W,1,05,2.2,184.1,M,-34.0,M,63
$GPRMC,135847.0,A,4xx2.525468,N,08xx5.972681,W,0.0,0.0,190620,5.1,W,A03
$GPGSA,A,2,08,11,13,28,30,2.4,2.2,1.037
The GPGGA sentence shows our altitude, but as you can see, the GPGSA string is in Automatic mode and a 2D fix. I believe this is the issue why the EM7455 card isn’t passing the 3D GPS coordinates to our data acquisition program.
Any advice on how to fix this?