我试图找到目的地点,给定起点lat / long,轴承&距离.下面这个网站的计算器给了我所需的结果.
http://www.movable-type.co.uk/scripts/latlong.html
当我尝试通过代码实现相同的时候,我没有得到正确的结果.
以下是我的代码 –
private GLatLng poinTradialdistance(double lat1,double lon1,double radianbearing,double radialdistance) { double rEarth = 6371.01; lat1 = DegreetoRadian(lat1); lon1 = DegreetoRadian(lon1); radianbearing = DegreetoRadian(radianbearing); radialdistance = radialdistance / rEarth; double lat = Math.Asin(Math.Sin(lat1) * Math.Cos(radialdistance) + Math.Cos(lat1) * Math.Sin(radialdistance) * Math.Cos(radianbearing)); double lon; if (Math.Cos(lat) == 0) { // Endpoint a pole lon = lon1; } else { lon = ((lon1 - Math.Asin(Math.Sin(radianbearing) * Math.Sin(radialdistance) / Math.Cos(lat)) + Math.PI) % (2 * Math.PI)) - Math.PI; } lat = RadianToDegree(lat); lon = RadianToDegree(lon); GLatLng newLatLng = new GLatLng(lat,lon); return newLatLng; } public double bearing(double lat1,double long1,double lat2,double long2) { //Convert input values to radians lat1 = DegreetoRadian(lat1); long1 = DegreetoRadian(long1); lat2 = DegreetoRadian(lat2); long2 = DegreetoRadian(long2); double deltaLong = long2 - long1; double y = Math.Sin(deltaLong) * Math.Cos(lat2); double x = Math.Cos(lat1) * Math.Sin(lat2) - Math.Sin(lat1) * Math.Cos(lat2) * Math.Cos(deltaLong); double bearing = Math.atan2(y,x); return bearing; } public double DegreetoRadian(double angle) { return Math.PI * angle / 180.0; } public double RadianToDegree(double angle) { return 180.0 * angle / Math.PI; }
从主程序,我调用子程序如下 –
double bearing = bearing(-41.294444,174.814444,-40.90521,175.6604); GLatLng endLatLng = poinTradialdistance(-41.294444,bearing,80);
我得到以下结果 –
bearing=1.02749621782165 endLatLng=-40.5751022737927,174.797458881699
我期望的答案是-40.939722,175.646389(从上面的网站链接).
解决方法
这是一些实现你想要做的代码.
public static GeoLocation FindPointAtdistanceFrom(GeoLocation startPoint,double initialbearingradians,double distanceKilometres) { const double radiusEarthKilometres = 6371.01; var distRatio = distanceKilometres / radiusEarthKilometres; var distRatioSine = Math.Sin(distRatio); var distRatioCosine = Math.Cos(distRatio); var startLaTrad = degreesToradians(startPoint.Latitude); var startLonRad = degreesToradians(startPoint.Longitude); var startLatCos = Math.Cos(startLaTrad); var startLatSin = Math.Sin(startLaTrad); var endLaTrads = Math.Asin((startLatSin * distRatioCosine) + (startLatCos * distRatioSine * Math.Cos(initialbearingradians))); var endLonRads = startLonRad + Math.atan2( Math.Sin(initialbearingradians) * distRatioSine * startLatCos,distRatioCosine - startLatSin * Math.Sin(endLaTrads)); return new GeoLocation { Latitude = radiansTodegrees(endLaTrads),Longitude = radiansTodegrees(endLonRads) }; } public struct GeoLocation { public double Latitude { get; set; } public double Longitude { get; set; } } public static double degreesToradians(double degrees) { const double degToRadFactor = Math.PI / 180; return degrees * degToRadFactor; } public static double radiansTodegrees(double radians) { const double radToDegFactor = 180 / Math.PI; return radians * radToDegFactor; }
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