GPSMAP 67 RINEX data

[JungleJim]

Out of curiosity and interest I was taking a look at the RINEX data captured by the GPSMAP 67. But I'm seeing some things I do not understand, so maybe someone here has some RINEX knowledge and would be able to explain?

If it's too technical for the GPSMAP 67 forum feel free to move it to another forum

I attached the complete RINEX file to this post (zipped). I also sent Garmin Product Support an email with the same questions.

67 RINEX file

grmn099n35.zip

Anyway I noticed the following:

• BDS header OBS TYPES missing B2a band observation descriptors, which means no B2a observation records although the device does use B2a band
• there are a lot of duplicate observation records, ie same satellite number and observation data. Could be a coincidence, but we have Bug 2 where the satellite page displays duplicate bars for the same satellite...
• the number of satellites observed does not match observations. Each EPOCH record includes the number of satellites observed, but this number does not match the actual number of observation records, even with all duplicates removed...
• missing L5 data for GPS, Galileo (possibly QZSS but cannot test). I do not understand enough of RINEX to check from which band the observation records are, but it is strange that each observation record only has max four observation data present even though the header specifies eight...
• BDS satellite number does not comply to RINEX format (1 letter followed by two numbers), instead I'm seeing a letter followed by 10 numbers: for example satellite numbers E4294967161 or C4294967138...
• no GLONASS SLOT / FRQ # header record. I guess this means that you cannot reliably determine what Glonass Satellite was observed and which frequency?
• time of first observation missing time system identifier (required in mixed observation file). I guess not a big deal because all times seem to be UTC but still not compliant to the RINEX spec

Are these indeed issues? And how reliable is the RINEX data? I guess not many end users will use this feature, but still...

And do the other RINEX capable devices (Montana 700 series, GPSMAP 66 series) have the same issues?

[GPSrChive]

Excellent post!

I am very interested to hear what Garmin have to say as I have not been able to get any website to read or accept any RINEX data captured on my Garmin devices.

If Garmins format is not accepted by others, it is useless.

[mimichris]

Rinex du 67 :

Capture-1.jpg

Rinex du 66sr :

Capture-2.jpg

*** Image formatting corrected to comply with forum guidelines ***

Conclusion, there are no satellite systems on the 67.....

[JungleJim]

mimichris, can you share the original RINEX file for the graph of the 66sr? Would be interesting to compare the source data!

[mimichris]

mimichris, can you share the original RINEX file for the graph of the 66sr? Would be interesting to compare the source data!

link to the Rinex file of the 66sr, which is on the chart.

66sr RINEX file

grmn004h26.zip

*** Hyperlink formatting corrected to comply with forum guidelines ***

*** Hyperlink replaced with *.zip file to ensure continuity of file availability ***

[mimichris]

From the graph in the Rinex file of the 67, it seems that the GPS system works intermittently, because you only see dots instead of having solid lines like the 66sr, which also explains the low consumption. Does this make the accuracy less good?
Then the satellites are not all present as on the 66sr, curious as operation.

[JungleJim]

The 66sr looks RINEX data indeed much better than the 67 data. The data in the observation records match the number of observation types specified, the number of observed satellites matches the number of observation records, no duplicate observation records and the Galileo satellite numbers have the correct format.

In other words, the 67 RINEX data is pretty much useless in this state... Hopefully Garmin responds to my report, but their responsiveness to emails has been very poor.

[JungleJim]

And firmware 4.80 brings no difference in the captured RINEX data.

[mimichris]

And firmware 4.80 brings no difference in the captured RINEX data.

Have you updated your 67 with firmware 4.80?

[JungleJim]

Have you updated your 67 with firmware 4.80?

Yes, I have updated my unit with 4.80.