How to draw circle on the MAP using GMAP.NET in C#

Question

I am using GMAP.NET in c#. I am able to display the map on the form, now i am trying to draw a CIRCLE mouse by clicking on a certian point, keeping the left mouse button an

Answer 1

I hit the same problem and on entry I had Lon, Lat and radius, here is my solution. It works like a charm :)

private void CreateCircle(Double lat, Double lon, double radius)
{
   PointLatLng point = new PointLatLng(lat, lon);
   int segments = 1000;

   List gpollist = new List();

   for (int i = 0; i < segments; i++)
      gpollist.Add(FindPointAtDistanceFrom(point, i, radius / 1000));

   GMapPolygon gpol = new GMapPolygon(gpollist, "pol");

   markers.Polygons.Add(gpol);
}

public static GMap.NET.PointLatLng FindPointAtDistanceFrom(GMap.NET.PointLatLng 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.Lat);
   var startLonRad = DegreesToRadians(startPoint.Lng);

   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 GMap.NET.PointLatLng(RadiansToDegrees(endLatRads), RadiansToDegrees(endLonRads));
}

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;
}

call

CreateCircle(51.640980, -2.673544, 1143.899431);