cesium 方位角测量绘线

Cesium中，可以使用以下步骤进行方位角测量绘线：
1.设置操作模式为“drawPloy”。
2.创建一个空数组tempPoints来存储绘制的点。
3.使用Cesium.ScreenSpaceEventHandler监听场景的左击事件，获取点击位置的经纬度坐标，并将其添加到tempPoints数组中。
4.根据tempPoints数组中的点绘制线段和点。
5.计算线段的方位角并显示在屏幕上。

以下是示例代码：

var viewer = new Cesium.Viewer('cesiumContainer');
var handler;
var tempPoints = [];

// 设置操作模式为“drawPloy”
function SetMode(mode) {
  if (mode == "drawPloy") {
    tempPoints = [];
    handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
    handler.setInputAction(function(click) {
      var cartesian = viewer.camera.pickEllipsoid(click.position, viewer.scene.globe.ellipsoid);
      if (cartesian) {
        var cartographic = Cesium.Cartographic.fromCartesian(cartesian);
        var longitudeString = Cesium.Math.toDegrees(cartographic.longitude);
        var latitudeString = Cesium.Math.toDegrees(cartographic.latitude);
        tempPoints.push({
          lon: longitudeString,
          lat: latitudeString
        });
        var tempLength = tempPoints.length;
        drawPoint(tempPoints[tempPoints.length - 1]);
        if (tempLength > 1) {
          drawLine(tempPoints[tempPoints.length - 2], tempPoints[tempPoints.length - 1], true);
          var azimuth = calculateAzimuth(tempPoints[tempPoints.length - 2], tempPoints[tempPoints.length - 1]);
          showAzimuth(azimuth, tempPoints[tempPoints.length - 1]);
        }
      }
    }, Cesium.ScreenSpaceEventType.LEFT_CLICK);
  }
}

// 绘制点
function drawPoint(point) {
  var pointEntity = viewer.entities.add({
    position: Cesium.Cartesian3.fromDegrees(point.lon, point.lat),
    point: {
      pixelSize: 10,
      color: Cesium.Color.YELLOW
    }
  });
}

// 绘制线段
function drawLine(startPoint, endPoint, isTemp) {
  var lineEntity = viewer.entities.add({
    polyline: {
      positions: [Cesium.Cartesian3.fromDegrees(startPoint.lon, startPoint.lat), Cesium.Cartesian3.fromDegrees(endPoint.lon, endPoint.lat)],
      width: 5,
      material: isTemp ? Cesium.Color.RED : Cesium.Color.GREEN
    }
  });
}

// 计算方位角
function calculateAzimuth(startPoint, endPoint) {
  var startLat = Cesium.Math.toRadians(startPoint.lat);
  var startLon = Cesium.Math.toRadians(startPoint.lon);
  var endLat = Cesium.Math.toRadians(endPoint.lat);
  var endLon = Cesium.Math.toRadians(endPoint.lon);
  var y = Math.sin(endLon - startLon) * Math.cos(endLat);
  var x = Math.cos(startLat) * Math.sin(endLat) - Math.sin(startLat) * Math.cos(endLat) * Math.cos(endLon - startLon);
  var azimuth = Math.atan2(y, x);
  azimuth = Cesium.Math.toDegrees(azimuth);
  azimuth = (azimuth + 360) % 360;
  return azimuth;
}

// 显示方位角
function showAzimuth(azimuth, endPoint) {
  var azimuthEntity = viewer.entities.add({
    position: Cesium.Cartesian3.fromDegrees(endPoint.lon, endPoint.lat),
    label: {
      text: 'Azimuth: ' + azimuth.toFixed(2),
      font: '16px sans-serif',
      fillColor: Cesium.Color.YELLOW,
      outlineColor: Cesium.Color.BLACK,
      outlineWidth: 2,
      style: Cesium.LabelStyle.FILL_AND_OUTLINE,
      pixelOffset: new Cesium.Cartesian2(0, -20),
      eyeOffset: new Cesium.Cartesian3(0, 0, -100)
    }
  });
}