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

[Peter Hartl]

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