Getting Band from MSM messages?

[gytisgreitai]

Hey,

so I can resolve signal ID by doing cell2prn on a RTCMMessage . But how do I get the Band (e.g. in case of 1097 for Galileo that would be E1/E5 etc.) ? Am I missing something obvious, or rtcmtables.py does not have that information, and my best bet would be to create a map from rinex304 which would map the signal tables *_SIG_MAP to bands ?

Thanks!

[semuadmin]

Hi @gytisgreitai

You're on the right track - provided you have the keyword argument labelmsm set to true (the default), pyrtcm will parse relevant MSM message attributes with a label signifying both the PRN and the signal RINEX code - see https://github.com/semuconsulting/pyrtcm/blob/main/src/pyrtcm/rtcmtables.py. Each signal RINEX code corresponds to a frequency band and signal channel.

So, for example, a value of DF405_10(014,5I) signifies PRN 14 and a signal RINEX code of 5I, which corresponds to the frequency band/signalE5a/I. A value of DF405_10(023,1A) signifies PRN 23 and a signal RINEX code of 1A which corresponds to frequency band/signal E1/A. The frequency-signal ID mappings for each constellation are given in the proprietary RTCM3 specification (which I can't reproduce in full here for copyright reasons), but this information can be found in public domain RINEX documentation, e.g. from RINEX 3.04 section 5.1 observation codes:

Hope this helps.

[gytisgreitai]

Hey, thanks for detailed answer!

The frequency-signal ID mappings for each constellation are given in the proprietary RTCM3 specification (which I can't reproduce in full here for copyright reasons)

So what you are saying is that one can't put something like this in their github repo?

GPS_SIGAL_TO_BAND = {
  'rinex_code': 'band',
 <...>
}

GLONASS_SIGAL_TO_BAND = {
  'rinex_code': 'band',
 <...>
}

etc.

Cause I've mapped the codes from the docs, and wrote a simple python script to print the GNSS system + satellite + bands I'm seeing, e.g.:

GPS 2(L1,L2) 3(L1,L2,L5) 4(L1,L2,L5) 6(L1,L2,L5) 9(L1,L2,L5) 17(L1,L2) 19(L1,L2) 21(L1,L2) 31(L1,L2) 32(L1,L2,L5)
GALILEO 7(E1,E5b,E5,E5a) 10(E1,E5b,E5,E5a) 12(E1,E5b,E5,E5a) 19(E1,E5b,E5,E5a) 26(E1,E5b,E5,E5a) 33(E1,E5b,E5,E5a)
GLONASS 1(G1,G2) 2(G1,G2) 3(G1,G2) 11(G1,G2) 12(G1,G2) 17(G1,G2) 18(G1,G2)

[semuadmin]

Provided the information is in the public domain, there's nothing stopping it being incorporated into a public GitHub repo like pyrtcm - I just can't upload the RTCM3 specification itself here.

My labelmsm function uses the the signal RINEX ID for brevity, as it contains all the information most end users would need, but if you fancy submitting a PR to add this additional lookup, be my guest!

[semuadmin]

@gytisgreitai

FYI I've just uploaded an enhancement in RC 1.0.13 which hopefully addresses your needs.

The cell2prn() method now includes an additional optional parameter sigcode, with values of:

• 0 = use frequency band
• 1 = use signal RINEX code (the current default behaviour)

The labelmsm keyword argument in RTCMReader and RTCMMessage has been updated accordingly:

• 0 = no MSM label
• 1 = label with PRN & signal RINEX code (the current default behaviour)
• 2 = label with PRN and frequency band

[gytisgreitai]

oh wow, that was fast, and works nicely. Thank you very much for a great library!