js版根据经纬度计算多边形面积（墨卡托投影）

[摘要：var earthRadiusMeters = 6371000.0; var metersPerDegree = 2.0 * Math.PI * earthRadiusMeters / 360.0; var radiansPerDegree = Math.PI / 180.0; var degr]
var earthRadiusMeters = 6371000.0;

var metersPerDegree = 2.0 * Math.PI * earthRadiusMeters / 360.0;

var radiansPerDegree = Math.PI / 180.0;

var degreesPerRadian = 180.0 / Math.PI;

var pointArr;

$(document).ready(function() {

	pointArr = new Array();

	b();

});

function calculateArea(points) {

	if (points.length > 2) {

		var areaMeters2 = PlanarPolygonAreaMeters2(points);

		if (areaMeters2 > 1000000.0) {

			areaMeters2 = SphericalPolygonAreaMeters2(points);

			alert("面积为" + areaMeters2 + "平方米");

		}

	}

}

/*球面多边形面积计算*/

function SphericalPolygonAreaMeters2(points) {

	var totalAngle = 0;

	for (var i = 0; i < points.length; i++) {

		var j = (i + 1) % points.length;

		var k = (i + 2) % points.length;

		totalAngle += Angle(points[i], points[j], points[k]);

	}

	var planarTotalAngle = (points.length - 2) * 180.0;

	var sphericalExcess = totalAngle - planarTotalAngle;

	if (sphericalExcess > 420.0) {

		totalAngle = points.length * 360.0 - totalAngle;

		sphericalExcess = totalAngle - planarTotalAngle;

	} else if (sphericalExcess > 300.0 && sphericalExcess < 420.0) {

		sphericalExcess = Math.abs(360.0 - sphericalExcess);

	}

	return sphericalExcess * radiansPerDegree * earthRadiusMeters * earthRadiusMeters;

}

/*角度*/

function Angle(p1, p2, p3) {

	var bearing21 = Bearing(p2, p1);

	var bearing23 = Bearing(p2, p3);

	var angle = bearing21 - bearing23;

	if (angle < 0) {

		angle += 360;

	}

	return angle;

}

/*方向*/

function Bearing(from, to) {

	var lat1 = from[1] * radiansPerDegree;

	var lon1 = from[0] * radiansPerDegree;

	var lat2 = to[1] * radiansPerDegree;

	var lon2 = to[0] * radiansPerDegree;

	var angle = -Math.atan2(Math.sin(lon1 - lon2) * Math.cos(lat2), Math.cos(lat1) * Math.sin(lat2) - Math.sin(lat1) * Math.cos(lat2) * Math.cos(lon1 - lon2));

	if (angle < 0) {

		angle += Math.PI * 2.0;

	}

	angle = angle * degreesPerRadian;

	return angle;

}

/*平面多边形面积*/

function PlanarPolygonAreaMeters2(points) {

	var a = 0;

	for (var i = 0; i < points.length; ++i) {

		var j = (i + 1) % points.length;

		var xi = points[i][0] * metersPerDegree * Math.cos(points[i][1] * radiansPerDegree);

		var yi = points[i][1] * metersPerDegree;

		var xj = points[j][0] * metersPerDegree * Math.cos(points[j][1] * radiansPerDegree);

		var yj = points[j][1] * metersPerDegree;

		a += xi * yj - xj * yi;

	}

	return Math.abs(a / 2);

}

function b() {

	var s = "112.523197631836,37.868892669677734;112.5170669555664,37.8605842590332;112.52099609375,37.849857330322266;112.54137420654297,37.8512732521875;112.5351180302734,37.858699798583984";

	var s1 = new Array()

	s1 = s.split(";");

	for (var i = 0; i < s1.length; i++) {

		var ss = s1[i];

		var temp = ss.split(",");

		var point = new Array();

		point.push(Number(temp[0]), Number(temp[1]));

		pointArr.push(point);

	}

	calculateArea(pointArr);

}
巴特西

js版根据经纬度计算多边形面积（墨卡托投影）

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