Height value in TerrainProvider (above sea level or above the ellipsoid)

CesiumJS
1

Hello, I’m developer of JapanGSITerrainProvider.
https://github.com/tilemapjp/Cesium-JapanGSI

Japan GSI (Geospatial Information Authority of Japan) provide height as “above sea level” in their ground height tile service,
so in my library, I pass it’s value directly to TerrainProvider, so my library is worked on “above sea level”.

But I found this description in Cesium’s reference:
https://cesiumjs.org/Cesium/Build/Documentation/Cartographic.html
“The height, in meters, above the ellipsoid.”

According to this, all height values must be given by above the ellipsoid…

I should get geoid data from somewhere and convert “above sea level” to “above the ellipsoid”?
Or, any switch to do it automatically in parent TerrainProvider class side?

Regards,
Kohei

2

Hello Kohei,

Yes, I believe we expect heights in the terrain provider to be relative to the WGS84 ellipsoid. I’m pretty sure these values are different than the height relative to sea level, so you will need to convert the values. We don’t have anything built in to do this calculation.

Best,

Hannah