3d-buildings-tiler clamptoground


I have a CityGML with elevattion/altitude egm96.
I would like to convert it to wgs84 - in ion I choose clampToGround and Cesium World Terrain.

As a result the buildings are over the terrain - using the adjust height sandcastle, I see that it is the original height.

What is the purpose of the clamptoground option - I expected, that my model is drapped on the Cesium World terrain or hs the heights of the world terrain and not the addition of both?

Has anyone a solution ?


Hello, @Ruediger_Brand. Thanks for your question and for your patience in waiting on a reply.

The Clamp to terrain option is there for the purpose you’re expecting: it attempts to place buildings on the terrain as accurately as possible.

Unfortunately, because the EGM96 projection is a global projection like WGS84, it can result in some level of inaccuracy when converting to WGS84.

Our recommendation is that the CityGML source data be in a regional coordinate system, so that errors are kept to a minimum when it is converted to WGS84.

If you are able to share your data with us, we can take a look internally.

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Hi Matt,

I think there isn’t any problem with the projection - the projection is in both cases the same WGS84, only the elevation/altitude is in a different system.

My observation is, that the clamptoground parameter adds the height/elevation of the terrain to the heights in the cityGML and that is in my opinion no " clamptoground"