private static Polygon GetInfluencePolygon(double?possibleLatitude, double?possibleLongtitude, double radius)
{
if (!possibleLatitude.HasValue || !possibleLongtitude.HasValue)
{
return(null);
}
var latitude = possibleLatitude.Value;
var longtitude = possibleLongtitude.Value;
Gps centre = new Gps(latitude, longtitude);
// In metres
double worldRadius = 6371000;
// In metres
Gps[] points = new Gps[20];
CirclePoints(points, centre, worldRadius, radius);
var polygon = new Polygon();
polygon.Extrude = true;
polygon.AltitudeMode = AltitudeMode.RelativeToGround;
polygon.OuterBoundary = new OuterBoundary();
polygon.OuterBoundary.LinearRing = new LinearRing();
polygon.OuterBoundary.LinearRing.Coordinates = new CoordinateCollection();
points.ToList <Gps>().ForEach(g =>
{
polygon.OuterBoundary.LinearRing.Coordinates.Add(new SharpKml.Base.Vector(g.Latitude, g.Longtitude, 30));
});
// close the circle
polygon.OuterBoundary.LinearRing.Coordinates.Add(new SharpKml.Base.Vector(points.First().Latitude, points.First().Longtitude, 30));
return(polygon);
}
private static void CirclePoints(Gps[] points, Gps centre, double R, double r)
{
int count = points.Length;
Vector C = centre.ToUnitVector();
double t = r / R;
Vector K = Math.Cos(t) * C;
double s = Math.Sin(t);
Vector U = K.Orthogonal();
Vector V = K.Cross(U);
// Improve orthogonality
U = K.Cross(V);
for (int point = 0; point != count; ++point)
{
double a = 2 * Math.PI * point / count;
Vector P = K + s * (Math.Sin(a) * U + Math.Cos(a) * V);
points[point] = P.ToGps();
}
}
