GPS firmware customization (more decimal places for altitude)?



Would it be possible to obtain a firmware customization for the PA6H/MT3339 module, so as to increase the number of decimal places for altitude reported in NMEA, please?

I understand the instantaneous stand-alone precision is not good, but our equipment is stationary, so averaging could improve results – provided the altitude values are not truncated.




To have specific features implemented you need to push this back into your commercial channel for us to be able to look at the business opp and also to discuss whether it is technically feasible.

With regards what you are asking, I suspect that the mediatek chpset will only supply the information to a certain level of accuracy, beyond that there will be nothing so I do not think it will technically make sense anyway.

Out of interest what is the use case?




@mlw, thanks for the information.

Our application is related to melting glaciers and icesheets.
One GPS is on bedrock (stationary) and another one is on the ice (moving).

The relative position obtained subtracting the two GPS
should be more accurate than the absolute position
of a stand-alone GPS.

Then further averaging several instantaneous positions
over several hours should further improve precision.

If only we had more decimal places to start with…




That is a cool application, RTCM is what this was sort of designed for but that has additional cost and of you want to do this over a wide area it is not really suitable and the averaging is what you really need to do.





we were hoping to try position-domain DGPS, so that we can keep using lower-cost NMEA modules, as described in the following paper:

“DGPS Enhancement to GPS NMEA Output Data: DGPS by Correction Projection to Position-Domain” <>

RTCM would be better, since it gives access to individual satellite raw data, enabling observation-domain DGPS. But as you note it’s more expensive and our sensors are meant to be disposable (it’s hard to recover them in the ice).

We’re asking different vendors if we can have one more decimal place in coordinates – just a matter of not truncating or rounding up the output, I guess. I understand it is just garbage for a stand-alone GPS, but we’re hoping to squeeze some precision via DGPS as noted above.