如何获取飞机穿过雷达两端的坐标

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首先说一下大致的实现步骤：

1. 创建雷达扫描的实体并定义飞机飞行的路线；
2. 利用通视分析的接口找到飞机进入和穿出雷达侦测范围的位置坐标；
3. 利用坐标构建线实体,雷达范围内为红色,范围外为绿色。

1. 创建雷达扫描的实体并定义飞机飞行的路线

首先创建雷达扫描实体，用添加实体的方式去添加雷达实体。
主要代码如下:

let sensorEntity = viewer.entities.add({
    position: Cesium.Cartesian3.fromDegrees(116.45093826887725, 39.90558654617389, 14.3030),
    rectangularSensor: new Cesium.RectangularSensorGraphics({
        radius: new Cesium.CallbackProperty(function () {
            return +self.radius;
        }, false),
        slice: 120,//切分程度
        xHalfAngle: new Cesium.CallbackProperty(function () {
            return Cesium.Math.toRadians(self.xHalfAngle);
        }, false),//左右夹角
        yHalfAngle: new Cesium.CallbackProperty(function () {
            return Cesium.Math.toRadians(self.yHalfAngle);
        }, false),//上下夹角
        lineColor: new Cesium.CallbackProperty(function () {
            return Cesium.Color.fromCssColorString(self.lineColor);
        }, false),//线颜色
        material: new Cesium.Color(0.0, 1.0, 1.0, 1),//统一材质
        showScanPlane: new Cesium.CallbackProperty(function () {
            return self.scanPlane;
        }, false),//显示扫描面
        scanPlaneColor: new Cesium.CallbackProperty(function () {
            return Cesium.Color.fromCssColorString(self.scanPlaneColor);
        }, false),//扫描面颜色
        scanPlaneMode: new Cesium.CallbackProperty(function () {
            return self.scanPlaneMode ? 'vertical' : 'horizontal';
        }, false),//垂直扫描模式
        scanPlaneRate: new Cesium.CallbackProperty(function () {
            return self.scanPlaneRate;
        }, false),//扫描速率
        showIntersection: true,//是否显示扫描与地球的线
        showThroughEllipsoid: false//是否穿过地球显示
    })
});

然后创建飞机飞行路线,让飞机沿线飞行。用的是时钟函数的方式去让飞机沿线飞行的。
主要代码：

// 飞机沿线飞行
var startTime = Cesium.JulianDate.fromDate(new Date(2019, 2, 25, 16));
var startPosition = Cesium.Cartesian3.fromDegrees(116.47326309033961, 39.90512322998635, 600);
var endTime = Cesium.JulianDate.addSeconds(startTime, 1000, new Cesium.JulianDate());
var endPosition = Cesium.Cartesian3.fromDegrees(116.4189181104128, 39.903026132659456, 600);
viewer.clock.startTime = startTime.clone();
viewer.clock.stopTime = endTime.clone();
viewer.clock.currentTime = startTime.clone();
viewer.clock.clockRange = Cesium.ClockRange.LOOP_STOP; //Loop at the end
viewer.clock.multiplier = 10;
viewer.timeline.zoomTo(startTime, endTime);
var carPositionProperty = new Cesium.SampledPositionProperty();
carPositionProperty.addSample(startTime, startPosition);
carPositionProperty.addSample(endTime, endPosition);
var carPosition = carPositionProperty.getValue(viewer.clock.currentTime);
var heading = Cesium.Math.toRadians(-3);
var pitch = 0;
var roll = 0;
var hpr = new Cesium.HeadingPitchRoll(heading, pitch, roll);
var orientation = Cesium.Transforms.headingPitchRollQuaternion(carPosition, hpr);
var carModel = viewer.entities.add({
    name: "gltf",
    position: new Cesium.CallbackProperty(function () {
        return carPosition;
    }, false),
    orientation: orientation,
    model: {
        uri: "./SampleData/gltf/客机模型/客机模型.gltf",
        scale: 60
    },
    viewFrom: new Cesium.Cartesian3(35, 70, 30)
});
viewer.clock.onTick.addEventListener(function () {
    var currentTime = Cesium.JulianDate.clone(viewer.clock.currentTime);
    carPosition = carPositionProperty.getValue(currentTime);
});

2. 利用通视分析的接口找到飞机进入和穿出雷达侦测范围的位置坐标

使用通视分析从起飞点到结束点进行分析得到靠近起飞点的第一个障碍点坐标；然后反过来进行通视分析得到远离起飞点的第二个障碍点坐标：
主要代码：

// 飞机起飞结束位置坐标: 
takeOffposition = [116.47326309033961, 39.90512322998635, 560]
finishposition = [116.4189181104128, 39.903026132659456, 560]
setTimeout(function () {
    // 通视分析判断点位.
    sightline.build();
    sightline.lineWidth = 3
    //设置观察点
    sightline.viewPosition = takeOffposition;
    // 设置目标点
    var flag = sightline.addTargetPoint({
        position: finishposition,
        name: "point0"
    });
}, 200)
// 获取障碍点的方法延时运行，因为通视分析需要时间
setTimeout(function () {
    sightline.getBarrierPoint("point0", function (e) {
        positions.fisrtObstacle = e.position
    })
    // 清除第一次的通视分析结果.
    sightline.removeAllTargetPoint();
    sightline.viewPosition = finishposition;
    var flag1 = sightline.addTargetPoint({
        position: takeOffposition,
        name: "point1"
    });
}, 300)
setTimeout(function () {
    sightline.getBarrierPoint("point1", function (e) {
        positions.secondObstacle = e.position
    })
    sightline.removeAllTargetPoint();
}, 380)

3. 利用坐标构建线实体,雷达范围内为红色,范围外为绿色。

这个比较简单直接附代码：

// 结束位置到第二个穿出雷达范围实体
viewer.entities.add({
    id: "test1",
    polyline: {
        positions: Cesium.Cartesian3.fromDegreesArrayHeights([positions.secondObstacle.longitude * (180 / Math.PI), positions.secondObstacle.latitude * (180 / Math.PI), positions.secondObstacle.height, finishposition[0], finishposition[1], finishposition[2]]),
        width: 4.0,
        material: Cesium.Color.GREEN.withAlpha(0.9),
        depthFailMaterial: Cesium.Color.GREEN.withAlpha(0.9)
    }
});
// 开始位置到进入雷达范围实体
viewer.entities.add({
    id: "test2",
    polyline: {
        positions: Cesium.Cartesian3.fromDegreesArrayHeights([positions.fisrtObstacle.longitude * (180 / Math.PI), positions.fisrtObstacle.latitude * (180 / Math.PI), positions.fisrtObstacle.height, takeOffposition[0], takeOffposition[1], takeOffposition[2]]),
        width: 4.0,
        material: Cesium.Color.GREEN.withAlpha(0.9),
        depthFailMaterial: Cesium.Color.GREEN.withAlpha(0.9)
    }
});
// 构建两个点中间被发现的线实体
viewer.entities.add({
    id: "test3",
    polyline: {
        positions: Cesium.Cartesian3.fromDegreesArrayHeights([positions.secondObstacle.longitude * (180 / Math.PI), positions.secondObstacle.latitude * (180 / Math.PI), positions.secondObstacle.height, positions.fisrtObstacle.longitude * (180 / Math.PI), positions.fisrtObstacle.latitude * (180 / Math.PI), positions.fisrtObstacle.height]),
        width: 4.0,
        material: Cesium.Color.RED.withAlpha(0.9),
        depthFailMaterial: Cesium.Color.RED.withAlpha(0.9)
    }
});

最终效果如下: