Map3D/MapGuide API中如何计算两点间的距离？

下面代码演示了Map 3D API中如何计算两点间的地球大圆距离和欧几里得距离，直接看代码：

[CommandMethod("ComputeDistance")]
public void ComputeDistance()
{
   double x1 = -87.7104750022991;
   double y1 = 43.7017449116101;
   double x2 = -87.703061972587;
   double y2 = 43.7016702994388;
   Editor ed = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Editor;
   //Get coordinate system of current map
   AcMapMap currentMap = AcMapMap.GetCurrentMap();
   string srsWkt = currentMap.GetMapSRS();
   //ed.WriteMessage("srs = " + srsWkt + "\n");
   MgCoordinateSystemFactory coordSysFactory = new MgCoordinateSystemFactory();
   MgCoordinateSystem coordSys = coordSysFactory.Create(srsWkt);
   //compute gread circle distance
   double distance = coordSys.MeasureGreatCircleDistance(x1, y1, x2, y2);
   distance = coordSys.ConvertCoordinateSystemUnitsToMeters(distance);
   ed.WriteMessage("gread circle dist = " + distance.ToString() + "\n");
   //compute Euclidean distance
   distance = coordSys.MeasureEuclideanDistance(x1, y1, x2, y2);
   distance = coordSys.ConvertCoordinateSystemUnitsToMeters(distance);
   ed.WriteMessage("Euclidean distance = " + distance.ToString() + "\n");
   //Another method, compute the distance from Newyork to Boston
   MgCoordinateSystemMeasure coordSysMeasure = coordSys.GetMeasure();
   double dist = coordSysMeasure.GetDistance(-74.806394, 40.714169, -71.061342, 42.355892);
   dist = coordSys.ConvertCoordinateSystemUnitsToMeters(dist);
   ed.WriteMessage(" distance = " + dist.ToString() + "\n");
}

 核心代码在MapGuide中也适用。