經緯度資料計算-JavaScript

• • 1.依據已知點、距離、角度擷取計算結果
  • 2.根據經緯度資料進行面積量算（采用橢球平均參數）

1.依據已知點、距離、角度擷取計算結果

常見情況下，在一直一點經緯度，已經相應的距離、角度資訊，計算獲得新坐标點的經緯度資訊。

var mapNumberUtil = {
		rad: function rad(d) {
			return d * Math.PI / 180.0;
		},
		deg: function deg(d) {
			return d * 180/ Math.PI
		}
	};
	/**
	* 根據一個經緯度及距離角度，算出另外一個經緯度
	* @param {*} lon 經度 113.3960698
	* @param {*} lat 緯度 22.941386
	* @param {*} brng 方位角 45 ---- 正北方：000°或360° 正東方：090° 正南方：180° 正西方：270°
	* @param {*} dist 90000距離(米)
	*/
	function getLonAndLat (lon, lat, brng, dist) {
		//大地坐标系資料WGS-84 極坐标長半徑a=6378137 極坐标短半徑b=6356752.3142 扁率f=1/298.2572236
		var a = 6378137;
		var b = 6356752.3142;
		var f = 1 / 298.257223563;
		var lon1 = lon * 1;
		var lat1 = lat * 1;
		var s = dist;
		var alpha1 = mapNumberUtil.rad(brng);
		var sinAlpha1 = Math.sin(alpha1);
		var cosAlpha1 = Math.cos(alpha1);
		var tanU1 = (1 - f) * Math.tan(mapNumberUtil.rad(lat1));
		var cosU1 = 1 / Math.sqrt((1 + tanU1 * tanU1)),
		sinU1 = tanU1 * cosU1;
		var sigma1 = Math.atan2(tanU1, cosAlpha1);
		var sinAlpha = cosU1 * sinAlpha1;
		var cosSqAlpha = 1 - sinAlpha * sinAlpha;
		var uSq = cosSqAlpha * (a * a - b * b) / (b * b);
		var A = 1 + uSq / 16384 * (4096 + uSq * ( - 768 + uSq * (320 - 175 * uSq)));
		var B = uSq / 1024 * (256 + uSq * ( - 128 + uSq * (74 - 47 * uSq)));
		var sigma = s / (b * A),
		sigmaP = 2 * Math.PI;
		while (Math.abs(sigma - sigmaP) > 1e-12) {
			var cos2SigmaM = Math.cos(2 * sigma1 + sigma);
			var sinSigma = Math.sin(sigma);
			var cosSigma = Math.cos(sigma);
			var deltaSigma = B * sinSigma * (cos2SigmaM + B / 4 * (cosSigma * ( - 1 + 2 * cos2SigmaM * cos2SigmaM) - B / 6 * cos2SigmaM * ( - 3 + 4 * sinSigma * sinSigma) * ( - 3 + 4 * cos2SigmaM * cos2SigmaM)));
			sigmaP = sigma;
			sigma = s / (b * A) + deltaSigma;
		}
		var tmp = sinU1 * sinSigma - cosU1 * cosSigma * cosAlpha1;
		var lat2 = Math.atan2(sinU1 * cosSigma + cosU1 * sinSigma * cosAlpha1, (1 - f) * Math.sqrt(sinAlpha * sinAlpha + tmp * tmp));
		var lambda = Math.atan2(sinSigma * sinAlpha1, cosU1 * cosSigma - sinU1 * sinSigma * cosAlpha1);
		var C = f / 16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha));
		var L = lambda - (1 - C) * f * sinAlpha * (sigma + C * sinSigma * (cos2SigmaM + C * cosSigma * ( - 1 + 2 * cos2SigmaM * cos2SigmaM)));
		var revAz = Math.atan2(sinAlpha, -tmp); // final bearing
		var lonLatObj = {
			lon: lon1 + mapNumberUtil.deg(L),
			lat: mapNumberUtil.deg(lat2)
		}
		
		return lonLatObj;
	}
           

2.根據經緯度資料進行面積量算（采用橢球平均參數）

//計算多邊形面積-以下參數為常見wgs84橢球相關平均參數
     var earthRadiusMeters = 6371000.0; // 平均地球半徑
     var metersPerDegree = 2.0 * Math.PI * earthRadiusMeters / 360.0; // 米-度轉換
     var radiansPerDegree = Math.PI / 180.0;  // 弧度-度轉換
     var degreesPerRadian = 180.0 / Math.PI; // 度-弧度轉換
     var pointArr;
     function SphericalPolygonAreaMeters(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.lat * radiansPerDegree;
         var lon1 = from.lon * radiansPerDegree;
         var lat2 = to.lat * radiansPerDegree;
         var lon2 = to.lon * 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;
     }