创建4490椭球体和切片方案

var cgs2000Ellipsolid = new Cesium.Ellipsoid(6378137.0, 6378137.0, 6356752.31414035585)；

var cgs2000GeographicProj = new Cesium.GeographicProjection(cgs2000Ellipsolid)；

var viewer = new Cesium.Viewer('cesiumContainer', {

      mapProjection: cgs2000GeographicProj,

    })