I found this while working on the new BaseAssist mode - where the firmware goes from Rover (with RTK Fix) to Fixed Base. I noticed that the altitude reported by Postcard (LG290P) was off by the MSL-Geoidal separation.

Using the RTK mosaic-X5 as my Base:
RTK mosaic-X5 is in Static mode
On its web page, it reports my Height (HGT) as 155.86m
For the RTCM 1006 position it reports to RTK2go, I see the same 155.86m reported at my SNIP::MOUNTPT

155.86m is my Ellipsoidal Height (WGS84)
My Height above MSL is 108.25m
A difference of 47.61m

If I have both a Postcard (LG290P) and a EVK (ZED-F9P) configured as Rovers with NTRIP Client connected to RTK2go
Both get RTK Fix

I have periodic printCurrentConditions enabled

printCurrentConditions calls gnss->getAltitude()

The EVK reports an altitude of 152m. That is correct for Ellipsoidal Height. The antenna is about 3m lower than the mosaic-X5 antenna.

The Postcard reports an altitude of 106m. That is correct for Height above MSL. The antenna is ~level with the mosaic-X5 antenna.

Note the difference of ~46m...

When I go from Rover mode into Fixed Base using the new BaseAssist route:

• The altitude from gnss->getAltitude() is copied across into settings.fixedAltitude
• gnss->getLatitude() is copied into settings.fixedLat
• gnss->getLongitude() is copied into settings.fixedLong
• settings.fixedBase is set true
• settings.fixedBaseCoordinateType is set to COORD_TYPE_GEODETIC

Afterwards:

Postcard reports an altitude of 58.89m
EVK reports an altitude of 154.6m

If I connect one Base then the other to RTK2go:

The reported Postcard altitude on RTK2go is 108.3m
The reporetd EVK altitude on RTK2go is 154.6m

It's a big old mess...