Question

我一直在使用Moveable-Type网站来帮助我进行一些Geocoordinate计算并且它非常有用，但是，我在计算两个坐标之间的中点时遇到了一个错误。我的结果接近预期，但不够接近：

posA = {47.64570362, -122.14073746}
posB = {47.64316917, -122.14032175}

预期结果（取自可移动型计算器）= 47°38'40“N，122°08'26”W = {47.644444, -122.140556}我的结果：{49.6054801645915, -122.14052959995759}

这是我的代码：

private Geocoordinate MidPoint(Geocoordinate posA, Geocoordinate posB)
{
   Geocoordinate midPoint = new Geocoordinate();

   double dLon = DegreesToRadians(posB.Longitude - posA.Longitude);
   double Bx = Math.Cos(DegreesToRadians(posB.Latitude)) * Math.Cos(dLon);
   double By = Math.Cos(DegreesToRadians(posB.Latitude)) * Math.Sin(dLon);

   midPoint.Latitude = RadiansToDegrees(Math.Atan2(Math.Sin(DegreesToRadians(posA.Latitude)) + Math.Sin(DegreesToRadians(posB.Latitude)), 
                Math.Sqrt((Math.Cos(DegreesToRadians(posA.Latitude)) + Bx) * (Math.Cos(DegreesToRadians(posA.Latitude))) + Bx) + By * By));

   midPoint.Longitude = posA.Longitude + RadiansToDegrees(Math.Atan2(By, Math.Cos(DegreesToRadians(posA.Latitude)) + Bx));

   return midPoint;
}

我有几种私有方法可以在Degrees和Radians之间进行转换。 E.g。

private double DegreeToRadian(double angle)
{
   return Math.PI * angle / 180.0;
}

我无法弄清楚为什么我的结果在Lat值上偏差了几度。有什么想法吗？

由于

Answer 1

你把一些括号弄错了。我在代码中标出了这个位置。

private Geocoordinate MidPoint(Geocoordinate posA, Geocoordinate posB)
{
   Geocoordinate midPoint = new Geocoordinate();

   double dLon = DegreesToRadians(posB.Longitude - posA.Longitude);
   double Bx = Math.Cos(DegreesToRadians(posB.Latitude)) * Math.Cos(dLon);
   double By = Math.Cos(DegreesToRadians(posB.Latitude)) * Math.Sin(dLon);

   midPoint.Latitude = RadiansToDegrees(Math.Atan2(
                Math.Sin(DegreesToRadians(posA.Latitude)) + Math.Sin(DegreesToRadians(posB.Latitude)),
                Math.Sqrt(
                    (Math.Cos(DegreesToRadians(posA.Latitude)) + Bx) *
                    (Math.Cos(DegreesToRadians(posA.Latitude)) + Bx) + By * By))); 
                 // (Math.Cos(DegreesToRadians(posA.Latitude))) + Bx) + By * By)); // Your Code

   midPoint.Longitude = posA.Longitude + RadiansToDegrees(Math.Atan2(By, Math.Cos(DegreesToRadians(posA.Latitude)) + Bx));

   return midPoint;
}

Answer 2

某些方法（例如WGS84惯例）包括地球的扁率。（at least that's what it says here）

两个坐标之间的地理中点

2 个答案: