Cesium's height value is altitude? or, above sea level?

Question

What is the Cesium(https://cesiumjs.org/)'s height value meaning? Altitude value from Ellipsoid? Or, above sea level?

Note: difference of altitude and above sea level is, [altitude] = [above sea level] + [Geoid value]

What I want to do is set Cesium's camera to same position of real GPS value get from Smartphone's GPS, but GPS's height value is altitude, so if Cesium use above sea level as it's height reference, Camera's position is set to too much high position...

Anyone know this?

Answer 1

I found the answer by myself:

https://cesiumjs.org/Cesium/Build/Documentation/Cartographic.html

"The height, in meters, above the ellipsoid."