使用cesiumjs

Question

使用cesiumjs，我想计算两点之间的仰角，好像我们站在第一点的热气球上一样。这些点是简单的制图点（纬度，长度，高度）。

这张照片总结得很好

经过一番研究，这是一种建议的方法：

  

将地球固定帧中的目标点转换为此局部   水平平面，你可以使用Transforms.eastNorthUpToFixedFrame。   返回一个Matrix4，然后再乘以你的目标点   矢量，产生一个新的向量。规范化该向量，然后对   仰角只是归一化矢量的asin（z）。

这是我放在一起的代码，但它返回NaN进行乘法运算。任何建议都将不胜感激。

var Cesium = require('cesium');

var startPoint = new Cesium.Cartesian3.fromDegrees(-107, 30, 3000);
var endPoint = new Cesium.Cartesian3.fromDegrees(-112, 25, 1000000);

//To transform your target point in the Earth-fixed frame to this local horizontal plane, you can use Transforms.eastNorthUpToFixedFrame.
var effTarget = Cesium.Transforms.eastNorthUpToFixedFrame(endPoint)
console.log("Earth-fixed frame (target): " + effTarget);

//That returns a Matrix4, which you then multiply your target point vector by, yielding a new vector.
var multiplicationResult = new Cesium.Cartesian3();
Cesium.Cartesian3.multiplyComponents(effTarget, endPoint, multiplicationResult)
console.log("Multiplication result: " + multiplicationResult)

//Normalize that vector
var normalizationResult = new Cesium.Cartesian3();
Cesium.Cartesian3.normalize(multiplicationResult, normalizationResult);
console.log("Normalize result: " + normalizationResult)

//and then the elevation angle is simply asin(z) of the normalized vector.
var elevationAngle = Math.asin(normalizationResult.z)
console.log("Elevation angle: " + elevationAngle)

Answer 1

基于Rachel Hwang's answer：

var startPoint = new Cesium.Cartesian3.fromDegrees(-107, 30, 3000);
var endPoint = new Cesium.Cartesian3.fromDegrees(-112, 25, 1000000);

// Obtain vector by taking difference of the end points.
var difference = Cesium.Cartesian3.subtract(endPoint, startPoint, new Cesium.Cartesian3());
difference = Cesium.Cartesian3.normalize(difference, new Cesium.Cartesian3());
console.log("Difference: " + difference);

// Obtain surface normal by normalizing the starting point position.
var surfaceNormal = Cesium.Cartesian3.normalize(startPoint, new Cesium.Cartesian3());
console.log("Surface normal: " + surfaceNormal);

// Take the dot product of your given vector and the surface normal.
var dotProduct = Cesium.Cartesian3.dot(difference, surfaceNormal);
console.log("Dot product: " + dotProduct);

// Arcos the result.
var angle = 90 - Cesium.Math.toDegrees(Math.acos(dotProduct));
console.log("Angle: " + angle);

控制台：

Difference: (-0.696260739885982, -0.7156821634654381, -0.05495473583645852)
Surface normal: (-0.2536245226271608, -0.8295684339468393, 0.4974844871160639)
Dot product: 0.7429570007551259
Angle: 47.9839196010689

Answer 2

我相信你正在使用错误的对象进行乘法运算。尝试使用.multiplyByPoint方法获取新的Cartesian3结果：

//That returns a Matrix4, which you then multiply your target point vector by, yielding a new vector.
var multiplicationResult = new Cesium.Cartesian3();
Cesium.Matrix4.multiplyByPoint(effTarget, endPoint, multiplicationResult)
console.log("Multiplication result: " + multiplicationResult)

您应该可以继续multiplicationResult。

Answer 3

这是正确的方向，但还不是很正确：

var startPoint = new Cesium.Cartesian3.fromDegrees(-107, 30, 3000);
var endPoint = new Cesium.Cartesian3.fromDegrees(-112, 25, 1000000);

//To transform your target point in the Earth-fixed frame to this local horizontal plane, you can use Transforms.eastNorthUpToFixedFrame.
var effTarget = Cesium.Transforms.eastNorthUpToFixedFrame(endPoint);
console.log("Earth-fixed frame (target): " + effTarget);

//That returns a Matrix4, which you then multiply your target point vector by, yielding a new vector.
var multiplicationResult = Cesium.Matrix4.multiplyByPointAsVector(effTarget, startPoint, new Cesium.Cartesian3());
console.log("Multiplication result: " + multiplicationResult);

//Normalize that vector
var normalizationResult = new Cesium.Cartesian3();
Cesium.Cartesian3.normalize(multiplicationResult, normalizationResult);
console.log("Normalize result: " + normalizationResult);

//and then the elevation angle is simply asin(z) of the normalized vector.
var elevationAngle = Math.asin(normalizationResult.z);
console.log("Elevation angle: " + Cesium.Math.toDegrees(elevationAngle));