Altitude offset GK DHDN + DHHN2016

[GeodatIQ]

Hello,

we have a project in the system DHDN / 3-degree Gauss-Kruger zone 3 (EPSG:31467), combined with the DHHN2016 as a vertical CS.  Our GCPs are measured in this system. After the Allignement and Clicking the GCPs I have a huge offset between the GCPs and the Coordinates of the cameras. For example if I deselect all the cameras and just calculate the Allignement with the GCPs 2,4m in the altitude, 3cm easting and 30cm northing.
I guess there is a problem in the convertion of the pictures to DHDN / 3-degree Gauss-Kruger zone 3 (EPSG:31467) + DHHN2016, but I cant find the problem.

If I activate both GCPs and pictures I have an offset at my GCPs of 30-50cm, which is not possible.
I experienced this problem at previous projects but never could find a solution to include GCPs and Coordinates of the drone.

Does anybody have an idea what the prolem could be. Thanks for your help.

[Paulo]

Hi GeodatIQ,

have you tried using a transformation grid for DHDN  to ETRS89 ( instead of 7 parameter transformation) : de_adv_BETA2007.tif,
and other for height from ETRS89 to DHHN2016 : GCG2016v2023.tif?

Should give you best results. Both files can be downloaded from Metashape geoids page.

Shown are differences in East and North for some 9 points between DHDN GK3 ( using 7 parameter transformation and DHDN GK3 using grid file BETA2007...

[GeodatIQ]

Hello Paulo,

I am not sure I understand correctly what you mean and how I would do that in Metashape, since I just made the normal 7 parameter transformation.

[Paulo]

Hello GeodatIQ,

What you can do is download the 2 mentioned files and put them in the Metashape geoids folder. Then when you create a chunk with following Compound CS:

Code: [Select]

Compound Coordinate System: DHDN / 3-degree Gauss-Kruger zone 3 + DHHN 2016 height
Projected Coordinate System: DHDN / 3-degree Gauss-Kruger zone 3 (EPSG::31467)
Linear Units: metre (EPSG::9001)
Projection Method: Transverse Mercator
    Latitude of natural origin: 0
    Longitude of natural origin: 9
    Scale factor at natural origin: 1
    False easting: 3500000
    False northing: 0
Geographic Coordinate System: DHDN (EPSG::4314)
Angular Units: degree (EPSG::9102)
Geodetic Datum: Deutsches Hauptdreiecksnetz (EPSG::6314)
Ellipsoid: Bessel 1841 (EPSG::7004)
Prime Meridian: Greenwich (EPSG::8901)
Vertical Coordinate System: DHHN2016 height (EPSG::7837)
Vertical Units: metre (EPSG::9001)
Vertical Datum: Deutsches Haupthoehennetz 2016 (EPSG::1170)
Then in Tools>Geoids, you should see the 2 tif files used in your chunk, one from DHDN to ETRS89 conversion (shift file de_adv_BETRA2007) and one for DHHN2016 height (file GCG2016v2023) as seen in following screen capture

Hope this can help,

[GeodatIQ]

Hello Paulo,

Thanks a lot for your help! I tested it in a small test project and seems to work.