L26-DR how to know when the module should use Dead Reckoning data vs data from satellites?

IoT Modules GNSS Module
1

Hi, the application note says the module sends the DR data in the $PSTMDRSTATE message, and the data received from satellites with messages like RMC, VTG, GGA, etc, so, if satellites are not available how to know which kind of messages should I use for positioning? I have read about 3 options:
1.- in the RMC messages the parameter Mode sends ‘E’ when we are using DR
2.- GSV messages has the parameter TotSats that are the total number of satellites in view
3. - GSV messages has the parameter SatxPRN that are the number of satellites using for positioning

so what would be the best option?

  • I read that a GNSS must have at least 4 satellites detected to work but I don’t know which of these parameters is useful with this data
2

Hi
No matter what the scenario, the data we need can be obtained through NMEA sentences. But the premise is that the module must be calibrated first, so that the output NMEA sentence is the fusion of GPS and DR.

For example, it is most obvious that in the case of a tunnel or a garage, the module will still output location information, which is the DR state without GNSS. And the GPSQual parameter of the GGA sentence shows 6.

Please refer to below :

  1. For module installation, please refer to chapter 6.4 of the hardware manual “Quectel_L26-DR_Hardware_Design_V1.1”.
  2. For the calibration procedure, please refer to chapter 6 of “Quectel_L26-DR_EVB_User_Guide_V1.2”.

Best Regards

3

Hi, ok I understand that the NMEA message is the fusion of both GPS and DR and when we are using DR we will get 6 in GPSQual parameter, if so, then why do we also receive the message $PSTMDRSTATE?, according to the Quectel L26-DR application note we receive a message from the DR status, in pag 24:

Besides, the message about vehicle speed will be output too:
$PSTMDRSTATE,<cpu_timestamp>,lat,lon,heading,speed…etc

So, if we are receiving info of the DR in the NMEA message GGA why do we need the message $PSTMDRSTATE?

4

Hi，

This message “$PSTMDRSTATE” reports a summary of current navigation and calibration estimates.The current navigation information is consistent with NMEA, the difference is that the DR calibration estimate is output.

Best Regards

5

Hi,

Blockquote
the difference is that the DR calibration estimate is output.

But the NMEA messages are outputs too

6

Hi，
Yes, but this does not conflict. Please get the information you need, other messages can be ignored or even closed.

Best Regards

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