Error importing DEM survey, EPSG code not found in EPSG supported files

[davidpp9]

When trying to import DEMs I get following error:

EPSG PCS/GCS code 6647 not found in EPSG support files. Is this a valid EPSG coordinate system?
--- Stacktrace ---
at OSGeo.GDAL.Band.GetUnitType()
at GCDConsoleLib.Raster._initfromfile() in D:\Code\gcd\gcd\GCDConsoleLib\Raster.cs:line 186
at GCDConsoleLib.GISDataset.get_Proj() in D:\Code\gcd\gcd\GCDConsoleLib\GISDataset.cs:line 19
at GCDCore.UserInterface.SurveyLibrary.GISDatasetValidation.DSHasSpatialRef(GISDataset gisDS, String sTypeSingle, String sTypePlural)
at GCDCore.UserInterface.SurveyLibrary.frmImportRaster.PrepareToImportRaster(Surface refSurface, Purposes purpose, String Noun, IntPtr parentWindow)
at GCDCore.UserInterface.Project.TreeNodeTypes.DEMSurveysGroup.OnAdd(Object sender, EventArgs e)
--- Exception Data ---
ArcMap = 10.8.1.14362
GCD = 7.5.0.0
Windows: Microsoft Windows NT 6.2.9200.0
Date: 2023-03-06 3:33:11 PM

The error tells me that the vertical coordinate system EPSG 6647 is not supported. Does it have to re-projected in a different vertical coordinate system? What vertical coordinate systems are supported?

Thanks!
David

[philipbaileynar]

https://spatialreference.org/ref/sr-org/6647/