根据鼠标移动的位置计算鼠标所在位置的经纬度
监听视角变化情况显示视高、方位角、俯仰角
监测底图切片等级来显示当前地图缩放等级

 showMapData() {
      let _this = this
      let handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas)
      handler.setInputAction(function (movement) {
        let pick = new Cesium.Cartesian2(
          movement.endPosition.x,
          movement.endPosition.y
        )
        if (pick) {
          let cartesian = viewer.scene.globe.pick(
            viewer.camera.getPickRay(pick),
            viewer.scene
          )
          if (cartesian) {
            let cartographic =
              viewer.scene.globe.ellipsoid.cartesianToCartographic(cartesian)
            if (cartographic) {
              let lontitude = Cesium.Math.toDegrees(
                cartographic.longitude
              ).toFixed(6)
              let latitude = Cesium.Math.toDegrees(
                cartographic.latitude
              ).toFixed(6)
              _this.lontitudeData = lontitude
              _this.latitudeData = latitude
              //  如果加了地形可以用这个去计算海拔
              //  let baseHeight = viewer.scene.sampleHeight(
              //   new Cesium.Cartographic(
              //     Cesium.Math.toRadians(cartographic.longitude), //转换成弧度
              //     Cesium.Math.toRadians(cartographic.latitude) //弧度
              //   )
              // );
              let h = viewer.scene.globe.getHeight(cartographic) //获取当前海拔高度
              h = h !== null && h !== undefined ? h.toFixed(0) : ""
              _this.baseHeight = h
            }
          }
        }
      }, Cesium.ScreenSpaceEventType.MOUSE_MOVE)
      viewer.camera.changed.addEventListener(() => {
        let heading = Cesium.Math.toDegrees(viewer.camera.heading).toFixed(2)
        let pitch = Cesium.Math.toDegrees(viewer.camera.pitch).toFixed(2)
        let viewHeight = viewer.camera.positionCartographic.height.toFixed(2)
        _this.headingData = heading
        _this.pitchData = pitch
        _this.viewHeight = viewHeight
        let tileRender = viewer.scene.globe._surface._tilesToRender
        if (tileRender && tileRender.length > 0) {
          this.mapLevelData = tileRender[0]._level
        }
      })
    },