my code
getLonLatByPick(position){
let earthPosition = this._viewer.camera.pickEllipsoid(position);
if(!earthPosition)return {}
let _height = this._viewer.scene.clampToHeight(earthPosition)
let cartographic = Cesium.Cartographic.fromCartesian(_height||earthPosition);
let lat = Cesium.Math.toDegrees(cartographic.latitude);
let lon = Cesium.Math.toDegrees(cartographic.longitude);
let height = cartographic.height
return {lon,lat,height}
}