[teqc] GLONAS SV ID 255 filter?

Lou Estey lou at unavco.org
Fri Jan 12 08:39:51 MST 2018


There will be no 3-digit numbers for SBAS in RINEX.  For RINEX 2, starting
at 2.10 (e.g. ftp://igs.org/pub/data/format/rinex211.txt):

--------
9.1 RINEX Observation Files for GEO Satellites

A new satellite system identifier has been defined for the geostationary
GPS signal payloads: "S", to be used in the RINEX VERSION / TYPE header line
and in the satellite identifier 'snn', nn being the GEO PRN number minus 100.

                    e.g.: PRN = 120 --> 'snn' = "S20"
--------

So two-digit IDs in RINEX for SBAS covers PRNs 100-199, although the smallest
defined PRN for SBAS is 120 and the largest, automatically allowed in teqc, is
currently 158.

A 255 for GLONASS from UBX RMX-RAWX messages is completely unrelated.  It just
means the receiver locked onto one of the GLONASS frequency channel numbers for
which it hasn't gotten a slot number ID yet for that SV from the SV's broadcast
navigation information ... and the firmware is stuffing in 0xff (= 255) for the
unknown ID.  (I suppose the firmware would could also used 0x00 = 0 as well.)

--lou

On 12-Jan-18 08:17 AM, lplopresti at enter.net wrote:
> Lou,
> 
> As we move forward it will be more common to use ranging distances from SBAS satellites to improve solutions, I believe the L5 correction 
> signal from SBAS is intended to also be used for ranging. In that case would it not be prudent to allow the possibility of a 3 digit number 
> to accommodate SBAS. In other words since a fix is necessary turn it into room for improvement. Thus bogus R255 (etc.) can be removed in 
> normal fashion.
> 
> Lawrence Paul Lopresti, PE, PLS


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