Thanks Greg,
QGIS interprets NMEA data as WGS84 geographic data which is correct!
I could not find to say to QGIS that it should use ETRS89 datum!
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)!
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!
Herzliche Grüße
Hartl Consulting e. U.
DI Peter Hartl MAS(GIS)
Gröben 11
A-6134 Vomp
Tel.: +43 660 17 42 228
[email protected]
www.hartl-consulting.at
Am 07.02.2025 um 14:51 schrieb Peter Hartl via QGIS-User:
Hallo Greg,
thanks for Information, will check NMEA RTK data in detail first.
Greetings
Peter Hartl
Von meinem iPhone gesendet
Am 07.02.2025 um 13:22 schrieb Greg Troxel via
QGIS-User<[email protected]>:
Peter Hartl via QGIS-User<[email protected]> writes:
GNSS NMEA interpreted as WGS84 in QGIS can do transformation with
gridshift from ETRS89 to MGI, that is alredy working very good.
What do you mean by "GNSS NMEA interpreted as WGS84"? What reference
frame is your GNSS data actually in? It could be
WGS84(G2159) if you are using a non-differential solution
ITRF? if you are using SBAS
ETRF? if you are using some RTK network
something else, if your receiver is combining 4 constellations, each
of which have their own frames, and doing something that they don't
document (hint: I have never seen any receiver document this.)
You should be aware that WGS84 is an ensemble, which means that when you
say data is in WGS84 that it is in one of several datums, and you don't
know which one.
The inherent accuracy limitation of the ensemble is about 2m. So
therefore a shift of 30 cm is not wrong.
Probably, it would be good to figure out how to not use WGS84,
especially if you are tryig to work at sub-meter accuracy. I have
done this by gathering data in NAD83(2011) epoch 2010.0, which is more
plate fixed, more or less analagous to ETRS89, using RTK with a
reference network operating in NAD83.
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