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gpsd_json(5) and cgps seem to differ


From: Bryan Christianson
Subject: gpsd_json(5) and cgps seem to differ
Date: Fri, 9 Jun 2023 16:07:46 +1200

I have gpsd: 3.25 (revision 3.25) installed and running on macOS 13.4 Ventura.

I have noticed that values I am seeing in the S and PRN columns of cgps seem to 
be at odds with the descriptions of the SKY/satellite fields 'svid' and 'PRN' 
as reported at gpsd_json(5) https://gpsd.gitlab.io/gpsd/gpsd_json.html. 

cgps is accurately reporting the same values as I see when looking at the json 
provided by gpspipe, so if there is a problem it is in the generation of the 
json stream and would be in gpsd itself.

Also - I think the numbers in the S column should be right justified. They're 
all squished up against the GNSS column. Not sure if this a macOS artefact or 
something easily fixed in cgps.

My receiver is a very cheap no-brand USB ubox-7 device and maybe this is the 
cause of the problem.

| Time         2023-06-09T03:56:03.000Z (18)││GNSS  S PRN  Elev  Azim   SNR Use│
│ Latitude          xx.xxxxxxxx S           ││GP  4     4  41.0   9.0  22.0  Y │
│ Longitude        yyy.yyyyyyyy E           ││GP  7     7  59.0 214.0  19.0  Y │
│ Alt (HAE, MSL)      81.591,     52.742  m ││GP  8     8  62.0  70.0  17.0  Y │
│ Speed              0.25              km/h ││GP  9     9  63.0 323.0  26.0  Y │
│ Track (true, var)     132.2,  19.9    deg ││GP 14    14  15.0 292.0  25.0  Y │
│ Climb            -20.82             m/min ││GP 16    16  21.0 127.0  29.0  Y │
│ Status          3D FIX (340 secs)         ││GP 27    27  42.0 122.0  35.0  Y │
│ Long Err  (XDOP, EPX)   0.58, +/-  8.7 m  ││GP 30    30  29.0 236.0  37.0  Y │
│ Lat Err   (YDOP, EPY)   0.67, +/- 10.0 m  ││GP  2     2   3.0  32.0   0.0  N │
│ Alt Err   (VDOP, EPV)   1.62, +/- 37.3 m  ││GP 20    20   2.0 238.0  23.0  N │
│ Speed Err (EPS)            +/- 72.0 km/h  ││GP 21    21   6.0  41.0  19.0  N │
│ Track Err (EPD)         n/a               ││GP 22    22   n/a   0.0   0.0  N │
│ Time offset             0.119176000     s ││SB122    35  28.0  57.0   0.0  N │
│ Grid Square             RFxxifyy          ││SB129    42  34.0 310.0   0.0  N │
│ ECEF X, VX   -5092288.190  m    0.300  m/s││SB134    47  47.0   5.0   0.0  N │
│ ECEF Y, VY     471007.460  m   -0.080  m/s││                                 │
│ ECEF Z, VZ   -3798837.690  m    0.170  m/s││                  

Regards, Bryan
-- 
Bryan Christianson
bryan@whatroute.net






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