By default Agisoft Metashape Professional assumes that the altitude values loaded to the Reference pane are estimated from the corresponding ellipsoid, however, in case the height should be estimated from the geoid it is necessary to select the corresponding compound system from the EPSG list or create the coordinate system that includes the vertical datum.
The instruction covers two cases:
- the compatible geoid file is available for downloading from Agisoft web-site;
- the geoid file should be created from the external file with the undulation grid data,
The steps below shows how the compound coordinate system can be created and the geoid model can be loaded:
1. Download the corresponding GeoTIFF from the geoids page of Agisoft web-site if available and put to /Metashape Pro/geoids/ folder and re-start Metashape Pro.
* In this example we are using "DVR90 geoid model (EPSG::5206)" > dvr90.tif file.
2. Open coordinate system selection dialog (for example, in the Reference pane settings) and locate the horizontal system that requires vertical datum to be applied and press Edit button.
* In the example we are using "ETRS89 / DKTM3 (EPSG::4095)" coordinate system.
3. Modify the new name of the coordinate system that will be created and in the "Vertical CS" field select the required vertical datum (geoid):
4. Modified coordinate system will appear in the section of User-defined coordinate systems and will be available for selection at any time (for example, during coordinate system conversion):
What to do, if the desired geoid is not present in the list on Agisoft's web-site, but you have an undulation grid file, that defines the offsets between the ellipsoid and geoid:
1. Open coordinate system selection dialog (for example, in the Reference pane settings) and locate the horizontal system that requires vertical datum to be applied and press Edit button.
* In this example we are using ETRS89 / UTM zone 28N (EPSG::25828) system.
2. Modify the new name of the coordinate system that will be created:
3. In the Vertical CS field click on Custom option in the beginning of the list, then in the newly opened dialog input the name of the vertical CS that is planned to be used:
4. Select "Add..." option in the Datum field, in the file browser window select the file with the undulation grid in one of the supported formats (ASCII Grid (*.grd), AUSGeoid Data Format (*.dat, *.txt), US National Geoidetic Survey (*.bin), Natural Resources Canada (*.byn), Trimble GGF (*.ggf), Carlson Geoid separation file (*.gsf), ISG (*.isg), Frensh Geoid Model (*.mnt), Sideris grid format (*.sid), Table Lat/Lon/Alt or Lon/Lat/Alt (*.txt), TIFF (*.tif, *.tiff)), click OK to confirm the selection.
5. Confirm the information for the geoid in the Import Geoid dialog and select the access parameters (for all users or for current user only - you can use the second option and then just copy the created geoid to the common folder to be accessed by all the users later):
6. Confirm the parameters in Edit Vertical Coordinate System dialog:
7. Confirm the modified coordinate system parameters:
8. Newly created modified coordinate system will appear in the section of User-defined coordinate systems and will be available for selection at any time: