How to use CesiumTerrainProvider to display Bathymetry of depths greater than 1000m

CesiumJS
1

Hi all,

I read in this post above that the height in the *.terrain tiles is unsigned short which means it is 16bit and has an upper limit of 65535. And because the height unit is 1/5 meter, the actual limit for its range is 13107 meters.

I am currently trying to use CesiumTerrainProvider to serve a terrain data that is a merge of topography (land elevation) and bathymetry, which means some regions of the world will have range greater than 13107. I am currently trying to resolve the -1000m limit within the ctb-tile tool (GitHub - geo-data/cesium-terrain-builder: A C++ library and associated command line tools designed to create terrain tiles for use in the Cesium JavaScript library) but even if I can resolve that, I still have the range limit.

Is there anyway the 1/5 meter unit can be tweaked on the client (CesiumJS) side?

2

It’s hacky, but you may be able to adjust terrainProvider._heightmapStructure.heightScale to a value of your choice.

Are you committed to using the heightmap format, or could you consider alternatives?

3

What I eventually did was making terrain data I am using to have the sea level at 9000m which covers all the area I am interested to be within the 13107m range. I then offset the ellipsoid the terrain is “covering” by -9000m (x,y,z of the Cartesian3) as well so it works seemingly with actual locations of czml data.

Do you forsee any problem with the approach above?

4

No major concerns there. Glad you found a workaround.