// radius is the half length of the bounding box you want in kilometers.
public static BoundingBox GetBoundingBox(MapPoint point, double radiusInKm)
{
// Bounding box surrounding the point at given coordinates,
// assuming local approximation of Earth surface as a sphere
// of radius given by WGS84
var lat = Deg2rad(point.Latitude);
var lon = Deg2rad(point.Longitude);
var halfSide = 1000 * radiusInKm;
// Radius of Earth at given latitude
var radius = WGS84EarthRadius(lat);
// Radius of the parallel at given latitude
var pradius = radius * Math.Cos(lat);
var latMin = lat - halfSide / radius;
var latMax = lat + halfSide / radius;
var lonMin = lon - halfSide / pradius;
var lonMax = lon + halfSide / pradius;
return new BoundingBox
{
MinPoint = new MapPoint { Latitude = Rad2deg(latMin), Longitude = Rad2deg(lonMin) },
MaxPoint = new MapPoint { Latitude = Rad2deg(latMax), Longitude = Rad2deg(lonMax) }
};
}
private const double WGS84_b = 6356752.3; // Minor semiaxis [m]
public static double HaversineDistance(MapPoint pos1, MapPoint pos2, DistanceUnit unit)
{
double R = (unit == DistanceUnit.Miles) ? 3960 : 6371;
var lat = Deg2rad(pos2.Latitude - pos1.Latitude);
var lng = Deg2rad(pos2.Longitude - pos1.Longitude);
var h1 = Math.Sin(lat / 2) * Math.Sin(lat / 2) +
Math.Cos(Deg2rad(pos1.Latitude)) * Math.Cos(Deg2rad(pos2.Latitude)) *
Math.Sin(lng / 2) * Math.Sin(lng / 2);
var h2 = 2 * Math.Asin(Math.Min(1, Math.Sqrt(h1)));
return R * h2;
}
