LC29H NMEA precision

IoT Modules GNSS Module
1

Hi - I am working with an LC29H evaluation board. I have obtained RTK position fixes, but the NMEA output precision is not sufficient to report the full accuracy of the position fixes - the height is limited to one decimal place, i.e. 10cm. I note that in V1 of the protocol specification there was a command to change the precision (098 PAIR_COMMON_SET_NMEA_POS_DECIMAL_PRECISION), and whilst the board acknowledges this command and appears to register the updated precision, the NMEA output does not change. I also note that in V1.1 of the protocol specification this command is no longer mentioned.

Currently the NMEA precision is 6 decimals of latitude and longitude minutes (approx 2mm in latitude) and 1 decimal of height - a combination that doesn’t match any of those defined for the $PAIR098 command.

Is there a newer firmware, or perhaps a configuration command, that will change the NMEA height precision to 3 decimal places?

2

I can confirm this, with Waveshare’s LC29H(DA) RPi hat NMEA message gives:

image
image752×21 1.81 KB

Versioinfo: $PQTMVERNO,LC29HDANR11A01S_RSA,2023/03/02,12:43:39*21

Altitude resolution is 10cm, should be 1cm. This is fairly speaking annoying. Is there fix e.g. firmware update for this.

3

Hi CHill,

Please check your firmware by sending $PQTMVERNO*58.

You can change NMEA decimals by sending

  1. $PQTMCFGNMEADP,W,3,6,3,2,3,2*37 -->configure ALT to 3 decimals
  2. $PQTMSAVEPAR*5A → save parameter
    image
    image688×678 56 KB

    image
    image519×746 59.8 KB

Best regards.

4

Hi Anviltop,

From your log, the module didn’t get RTK fixed. But it was differential mode and received correction data from base stations. Did the module get RTK fixed finally?
The module can’t reach 1cm accuracy under differential mode.
image

If you need to change decimals, you can refer to the previous comment.

Best regards.

5

Thank you Raphael - that seems to be the command I was looking for. Can you tell me where I can obtain the document that this image was taken from? That instruction is not documented in version 1.1 of the protocol specification for these modules:

I will check the current firmware version the next time I am in the lab.

Thanks

6

Hi Chill,

Quectel don’t provide any link for document downloading. I will send you the Protocol spec via message.

Best regards.

7

Thanks Raphael, received with thanks.

May I ask why this updated document is not available in the download zone? It would surely help other users.

Thanks
Chris

8

Hi Raphael

I can confirm that I’ve been able to change the altitude precision to 3 decimal places, thank you.

Version info: $PQTMVERNO,LC29HBANR11A02S_CSA4,2023/06/06,17:28:08*0A

I also have a base station that reports: $PQTMVERNO,LC29HBSNR11A01S,2023/02/13,10:14:06*27

Are there newer versions of the firmware that I should be using?

Thanks
Chris

1 Like
9

Hi Raphael!

I can also confirm, like chill:
image

Thanks Raphael fo your assistant!

10

Hi Chill,

You already have the latest LC29HBA and LC29HBS firmware.

Best regards

1 Like
11

Dear Raphael-Q.

Could you please send me this document as well? I am having trouble as well finding some documentation on configuration messages to get precision output.

With kind regards,

Mathijs

12

Hi Mathijs,

I will send you protocol specification via message.

Can you query the firmware that you curruently use? Please send $PQTMVERNO*58 to the module.

Please feel free to launch a new topic in GNSS block with your problems. I will be much easier for me to trace your issue.

Best regards

13

$PQTMVERNO,LC29HEANR11A02S_RSA,2023/02/07,15:24:42*2D

I just used that in another topic :wink: