PA6H 2D fixes recorded as 3D fixes

IoT Modules XS Series (GNSS)
1

I have been investigating GPS fixes under conditions of poor satellite reception and have noticed that the PA6H module reports fixes containing significant errors as 3D fixes, when they appear to be 2D fixes (position error associated with height error).

(unable to attach files, new forum user)

In the Datasheet for the PA6H it states:
“Table-6: Mode 2 Value Description
1 Fix not available
2 2D (＜4 SVs used)
3 3D (≧4 SVs used)”

If this was implemented in firmware then 2D fixes using 4 or more SVs would be incorrectly identified as 3D fixes, which is what I am experiencing.

Is there a way to limit fixes to just 3D fixes?

I can upload files now…

NMEA LOG (934.9 KB) created by an Oudie 4 (naviter.com).

The Oudie also records a barometric height and produces an IGC file, so you can see the height errors easily. Its on the internet at http://sacra.biz/2dfixes/track02092018oudie.igc and can be opened with SeeYou (naviter.com). The height for 2D fixes (identified by $GPGSA,A,2 in the NMEA log) in this file are changed to 0. B record format is time/lat/long/A or V/baro height/GPS height/other stuff.

2

I have recently tested another manufacturers module and found the same type of error. Since it also uses the MT333x chipset I will contact MediaTek as the error is likely to be with this component.

3

Hi @weshill

Although you have confirmed that the same error have been found on another module using MT333x chipset, please push back this question to your commercial channel to get a ticket raised for our technical teams to investigation.

Regards,
Phillip