Math helper extensions for cartographic calculation in Cesium.js
npm install --save cesium cesium-cartographic
import * as cc from 'cesium-cartographic'
import * as Cesium from 'cesium'
cc.greatCircleGroundDistance(Cesium.Cartographic.fromDegrees(0, 0, 0), Cesium.Cartographic.fromDegrees(1, 1, 0))
See the documentation for the rest.
A huge thank you to Chris Veness for its JavaScript implementations in geodesy.