I recently stumbled on the “cesium-native” project. We have applications that use CesiumJS and fly live/historic flight data. Our flight data has elevations in MSL, so we currently use “EarthGravityModel1996.js” and the “WW15MGH.DAC” file to convert the altitude of every track point to a WGS84 height.
I’m wondering if there are methods in “cesium-native” that would allow us to convert MSL to WGS84 in a more efficient manner?
Hi @Rob - I’m not sure how this one slipped through the cracks, but I found this while we are reorganizing the forums to add a Cesium Native section and thought it would be worth giving an answer for the benefit of anyone else with this question coming across this topic. We’ve actually added support for EGM96 in Cesium Native with the CesiumGeospatial::EarthGravitationalModel1996Grid class. If you read the WW15MGH.DAC into a buffer of bytes, you can pass it to the EarthGravitationalModel1996Grid::fromBuffer method to create an instance. You can then call sampleHeight with the cartographic position in question which will return the difference in meters between the position’s EGM96 altitude and the WGS84 ellipsoid!
It seems like the WW15MGH.DAC file has become hard to find - for some reason, it’s no longer listed on the NGA’s website - so we’ve included a copy in the Cesium Native repo, in the data directory.