[Qgis-user] QGIS GNSS NMEA Transformation Problem WGS84 to MGI Austria

[Greg Troxel]

Peter Hartl via QGIS-User <qgis-user at lists.osgeo.org> writes:

> QGIS interprets NMEA data as WGS84 geographic data which is correct!

No, it is not correct.  It is only correct it the receiver is operating
in WGS84.  That is true *only* for non-differential solutions.  That
means not with SBAS, not with RTK.

And, it's also not correct because WGS84 is an ensemble.

> I could not find to say to QGIS that it should use ETRS89 datum!

I think that's a missing feature.  The feature is missing in QField too:

  https://github.com/opengisch/QField/issues/2855


There's another problem, which is that proj, when asked to transform
from WGS84 to NAD83(2011) 2010.0, uses a null transform.  That
technically makes sense because WGS84(TRANSIT) is roughly equal to
NAD83(1986).  But it doesn't actually make sense.

> We are using *QField*, here Transformation in X, Y from GNNS into our
> MGI with gridshift is working correkt (Vertical girdshift works too
> very goo in cm accuracy)!

But what is the actual datum your NMEA is in?  What kind of GNSS are you
using?

> The *same QGIS projekt behind with QGIS* shows data in map correct
> (set to 25832) but in saving to 31254 it gets shift, without
> possibiltity for changing that for me.
>
> For me it looks like a issue in QGIS!

Maybe but you have not answered my questions about what is really going
on, and you may be operating in a mode where multiple bugs sometimes
cancel and sometimes do not.