arcgis for js如何自写算法实现地图量算工具

众所周知，使用arcgis api for js实现地图的量算工具功能，无非是调用arcgisserver的Geometry服务（http://localhost:6080/arcgis/r ... erver）提供的Areas and Lengths以及Lengths，如图：


但是我这里提供另一种实现的思路，就是自己写算法来实现距离以及面积的量算，这样的好处是不依赖arcgisserver几何服务，有些项目不排除有些奇特的客户不用Geometry服务的，最终的实现效果图如下：



具体实现思路：创建一个独立的js文件，里面有量算工具类DCIMeature，DCIMeature类构造函数传入地图对象map

construct: function (map) {  

    this._dciMap = map;  

    this._onClickHandler = dojo.hitch(this, this._onClickHandler);  

    this._onMouseMoveHandler = dojo.hitch(this, this._onMouseMoveHandler);  

    this._onDrawEndHandler = dojo.hitch(this, this._onDrawEndHandler);  

    this._onExtentChangeHandler = dojo.hitch(this, this._onExtentChangeHandler);  

    this._onGraphicClearHandler = dojo.hitch(this, this._onGraphicClearHandler);  

    this._graphicsLayer = new esri.layers.GraphicsLayer({ id: "DciMeatureGLyr" });  

}

核心算法测距：

DUtil.getDistanceInEarth = function (point1, point2) { 

var d = new Number(0); 

//1度等于0.0174532925199432957692222222222弧度 

//var radPerDegree=0.0174532925199432957692222222222; 

var radPerDegree = Math.PI / 180.0; 

if (DCI.Measure.map.spatialReference.wkid == "4326") { 

var latLength1 = Math.abs(this.translateLonLatToDistance({ x: point1.x, y: point2.y }).x - this.translateLonLatToDistance({ x: point2.x, y: point2.y }).x); 

var latLength2 = Math.abs(this.translateLonLatToDistance({ x: point1.x, y: point1.y }).x - this.translateLonLatToDistance({ x: point2.x, y: point1.y }).x); 

var lonLength = Math.abs(this.translateLonLatToDistance({ x: point1.x, y: point2.y }).y - this.translateLonLatToDistance({ x: point1.x, y: point1.y }).y); 

        d = Math.sqrt(Math.pow(lonLength, 2) - Math.pow(Math.abs(latLength1 - latLength2) / 2, 2) + Math.pow(Math.abs(latLength1 - latLength2) / 2 + Math.min(latLength1, latLength2), 2)); 

    } 

else { 

var len_prj = Math.pow((point2.x - point1.x), 2) + Math.pow((point2.y - point1.y), 2); 

        d = Math.sqrt(len_prj); 

    } 

    d = Math.ceil(d); 

return d; 

}; 

DUtil.translateLonLatToDistance = function (point) { 

var d = new Number(0); 

//1度等于0.0174532925199432957692222222222弧度 

//var radPerDegree=0.0174532925199432957692222222222; 

var radPerDegree = Math.PI / 180.0; 

var equatorialCircumference = Math.PI * 2 * 6378137; 

return { 

        x: Math.cos(point.y * radPerDegree) * equatorialCircumference * Math.abs(point.x / 360), 

        y: equatorialCircumference * Math.abs(point.y / 360) 

    }; 

}; 　

这里测距的算法有基于地理坐标系以及投影坐标系不同，有不同的计算公式来计算的
测面的核心算法：

//******求三角形面积**** 

DUtil.getTriangleArea = function (point1, point2, point3) { 

    var area = 0; 

    if (!point1 || !point2 || !point3) { 

        return 0; 

    } 

    if (DCI.Measure.map.spatialReference.wkid == "4326") { 

   

        point1 = this.translateLonLatToDistance(point1); 

        point2 = this.translateLonLatToDistance(point2); 

        point3 = this.translateLonLatToDistance(point3); 

    } 

    area = ((point1.x * point2.y - point2.x * point1.y) + (point2.x * point3.y - point3.x * point2.y) + (point3.x * point1.y - point1.x * point3.y)) / 2; 

    return area; 

}; 

测面算法也是类似，基于地理坐标系以及投影坐标系不同，有不同的计算公式来计算的；
完整的量算工具js文件下载点击打开链接
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