cesium工具：鼠标获取经纬度

	//获取经纬度
	getPosition = (viewer) => {
        //得到当前三维场景
        var scene = viewer.scene;
        //得到当前三维场景的椭球体
        var ellipsoid = scene.globe.ellipsoid;
        var entity = viewer.entities.add({
            label : {
                show : false
            }
        });
        var longitudeString = null;
        var latitudeString = null;
        var height = null;
        var cartesian = null;
        // 定义当前场景的画布元素的事件处理
        var handler = new Cesium.ScreenSpaceEventHandler(scene.canvas);
        //设置鼠标移动事件的处理函数，这里负责监听x,y坐标值变化
        handler.setInputAction(function(movement) {
            //通过指定的椭球或者地图对应的坐标系，将鼠标的二维坐标转换为对应椭球体三维坐标
            cartesian = viewer.camera.pickEllipsoid(movement.endPosition, ellipsoid);
            if (cartesian) {
                //将笛卡尔坐标转换为地理坐标
                var cartographic = ellipsoid.cartesianToCartographic(cartesian);
                //将弧度转为度的十进制度表示
                longitudeString = Cesium.Math.toDegrees(cartographic.longitude);
                latitudeString = Cesium.Math.toDegrees(cartographic.latitude);
                //获取相机高度
                height = Math.ceil(viewer.camera.positionCartographic.height);
                entity.position = cartesian;
                entity.label.show = true;
                entity.label.text = '(' + longitudeString + ', ' + latitudeString + "," + height + ')' ;
            }else {
                entity.label.show = false;
            }
        }, Cesium.ScreenSpaceEventType.MOUSE_MOVE);
        //设置鼠标滚动事件的处理函数，这里负责监听高度值变化
        handler.setInputAction(function(wheelment) {
            height = Math.ceil(viewer.camera.positionCartographic.height);
            entity.position = cartesian;
            entity.label.show = true;
			entity.label.text = '(' + longitudeString + ', ' + latitudeString + "," + height + ')' ;
			entity.label.fillColor = Cesium.Color.BLACK;
        }, Cesium.ScreenSpaceEventType.WHEEL);
    }