Sam,
can you possibly provide some details of how Cesium ion converts elevation data that was referenced to MSL into Ellipsoidal elevation? I am trying to work back from the value returned by sampleTerrainMostDetailed on my custom Terrain to get an elevation relative to MSL (i.e. I’m trying to get the original value of my data before it was converted by ion), using the EGM2008 Geoid Model to get difference between Ellipsoid & Geoid, but still getting differences of around 2m.
Regards