Re: gpsd_json(5) and cgps seem to differ

[Greg Troxel]

Bryan Christianson <bryan@whatroute.net> writes:

> Hi Gary and Greg
> In the gpsd_json manpage the description for PRN is 'PRN ID of the satellite. 
> 1-63 are GNSS satellites, 64-96 are GLONASS satellites, 100-164 are SBAS 
> satellites'
>
>> On 10/06/2023, at 7:07 AM, Gary E. Miller <gem@rellim.com> wrote:
>> 
>> On Fri, 9 Jun 2023 16:07:46 +1200
>> Bryan Christianson <bryan@whatroute.net> wrote:
>> 
>>> 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. 
>> 
>> Care to be more specific about what you think is off?
>
>
> The cgps output I posted has:
>
> │ 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 │
>
> I expected the PRN for SB satellites to be in the range 100-164

What is SB?  SBAS?

PRN is messy, and often confused with NMEA ids.  PRN is about the
over-the-air format in terms of deriving codes and NMEA is a codepoint
for talking about them.  However it does look like the actual GPS PRN
codes are in the the range you say, and NMEA ids like 48 are used
instead, leaving 65-96 for GLONASS.

https://www.gps.gov/technical/prn-codes/L1-CA-PRN-code-assignments-2023-Apr.pdf