How to create a Metashape file to use as a geoid?

[scannapieco]

I would like to know how I can create a file to use as a local geoid in Metshape starting from a TIFF file containing the point mesh with the corresponding differential values ​​N between ellipsoidal elevation and geoidal elevation.
This is a local geoid used in a particular Italian region.
I have the TIFF file created in UTM-ETRF89 coordinates, EPSG code 25832.
Is this still OK, or should it be created in WGS84?
Thank you very much.

[Paulo]

Hello,

I think the tiff file should br created in geographic ETRF89 coordinates.

If you share the file, I could convert it..

[scannapieco]

I have this file ....

[Paulo]

Hi scannapieco,

attached is the tif corresponding to Bolzano geoid. Please copy into the Metashape geoids folder (C:\Program Files\Agisoft\Metashape Pro\geoids).

And then you have an ETRS89 to Bolzano height geoid as seen in 2nd attachment.

[scannapieco]

Thank's Paulo.
Can you create a TIFF file of the grid for use in Metashape with this data set I'm sending you?
These are cartographic plane coordinates according to the ETRS89 / UTM zone 32N system, EPSG code 25832.
The altitude value represents the difference N (undulation) between this local geoid and the ellipsoid.
What do you use to create the TIFF file? With what options?
Could you explain the process to me?
I tried using Metashape, but when I import it as a geoid, it doesn't find the Vertical CS, as you can see in the screenshot I'm sending you.
I'll also send you the TIFF I created.
Thanks!!!

[Paulo]

Ciao,

first your trento bolzano geoide must be referenced to geographic coordinates not projected UTM. So I opened the the file in Global mapper and set the CS to ETRS89 geographic  and exported to new file TRENTO BOLZANO - geoide - ETRF89 .tif.

Then in Metashape using Tools/Geoids I use import button to select the above created file and use Custom in Vertical CS and input a name for Vertical System and vertical datum as in following screen capture. After selecting OK and OK I have the new grid file imported into geoids folder. see second capture..

I attach the Trento Bolzano geoid file to install into your Metashape installation directory geoids folder...

[scannapieco]

Ok,
Therefore, to import it into Metashape, it must be in geographic coordinates (longitude, latitude) and not in UTM coordinates.
So you performed a coordinate conversion with Global Mapper.
But why, if the initial mesh was 2 km x 2 km, is it now 1.69 km?
....
I think I did it...the one attached is a 2km x 2km link.
Can you confirm?