Postcard RTK: Choose msm4 or msm7 message format

[amlago]

Postcard RTK: Choose msm4 or msm7 message format

I need to choose the msm4 or msm7 message format.
The Postcard settings only allow you to choose between on and off.
I would like to be able to choose between msm4 and msm7, like in the Facet settings.
Regards
Angel

[amlago]

Hi, any answers on msm7 in Postcard RTK?
I need it urgently because I need rinex with full GLONASS data, and msm4 is missing phase data.
Regards

[PaulZC]

Hi Angel (@amlago ),

The LG290P MSM selection has changed frequently over the past few weeks as we add better support for PPP logging.

For MSM7, it looks like Release 2.2 may currently be your best option?

To make it 'switchable', we will need to add a new setting with full menu, command and configuration support, and implement it on all other supported GNSS platforms. It is certainly possible, and we will add it, but it is not a 'simple' change.

I hope this helps,
Paul

In the main branch (release v2.2):

enableRTCMBase :

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 801 in 68884d8

"PQTMCFGRTCM,W,7,0,-90,07,06,2,1"); // Enable MSM7, output regular intervals, interval (seconds)

enableRTCMRover :

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 941 in 68884d8

"PQTMCFGRTCM,W,7,0,-90,07,06,2,1"); // Enable MSM7, output regular intervals, interval (seconds)

In today's release_candidate (unreleased):

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 801 in 68884d8

"PQTMCFGRTCM,W,7,0,-90,07,06,2,1"); // Enable MSM7, output regular intervals, interval (seconds)

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 941 in 68884d8

"PQTMCFGRTCM,W,7,0,-90,07,06,2,1"); // Enable MSM7, output regular intervals, interval (seconds)

In release_candidate on September 30th:

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 853 in 5e8192f

"PQTMCFGRTCM,W,4,0,-90,07,06,2,1"); // Enable MSM4, output regular intervals, interval (seconds)

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 1013 in 5e8192f

snprintf(msmCommand, sizeof(msmCommand), "PQTMCFGRTCM,W,7,0,15,07,06,2,%d", minimumRtcmRate);

In release_candidate on September 22nd:

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 853 in b3b0492

"PQTMCFGRTCM,W,4,0,-90,07,06,2,1"); // Enable MSM4, output regular intervals, interval (seconds)

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 1013 in b3b0492

snprintf(msmCommand, sizeof(msmCommand), "PQTMCFGRTCM,W,7,0,15,07,06,2,%d", minimumRtcmRate);

In release_candidate on September 19th:

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 853 in ec5b17f

"PQTMCFGRTCM,W,4,0,-90,07,06,2,1"); // Enable MSM4, output regular intervals, interval (seconds)

SparkFun_RTK_Everywhere_Firmware/Firmware/RTK_Everywhere/GNSS_LG290P.ino

Line 1013 in ec5b17f

snprintf(msmCommand, sizeof(msmCommand), "PQTMCFGRTCM,W,7,0,15,07,06,2,%d", minimumRtcmRate);

[amlago]

Hi Paul.
Thanks for your concern.
I know each change is a lot of work.
Ideally, it should be switchable between msm4 and msm7.

Regards
Angel

[cturvey]

I didn't do a comprehensive search of the usage, initially threw it at the whole of GitHub to find the string/command, but this looked like the one file in the SparkFun domain.

I suspect having it adjustable is helpful, the MSM4 are definitely more compact and a better choice in lower bandwidth radio links where size and speed/latency are considerations, and data volume for logging.

MSM4 vs MSM7 there's also a precision aspect, the doppler can be inferred, and is often used in a code vs carrier sense to identify cycle slippage. When I was checking RINEX files I'd try and map the code and carrier advancement into Hz. The expectation being about +/- 3 KHz as I recall, but this pulls one way or another depending if the receiver's local clock is fast or slow. On uBlox they measure the clock rather than try an discipline it explicitly like say LEICA, and expand the doppler search space to perhaps +/- 5 KHz to find the skewed signal.

Ideally for RINEX that we use raw measurements more directly in a native form like uBlox's UBX-RXM-RAWX, where the post-processing solves for receiver time (offset, bias, drift, etc) it ends up with more information to work with and doesn't have to un-cook things. Not sure if Quectel has a raw format or if that just generates way more data than desired.

Best Regards, -Clive