///
/// Taken from http://stackoverflow.com/questions/238260/how-to-calculate-the-bounding-box-for-a-given-lat-lng-location?lq=1
/// See also http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates
// 'halfSideInKm' is the half length of the bounding box you want in kilometers.
/// <summary>
/// Compute the a box around the center point of 2x halfSideInKm.
/// </summary>
/// <param name="point">Center point to build a box around</param>
/// <param name="halfSideInKm">Half the size of the width/height of the box.</param>
/// <returns></returns>
public static LocationBoundry ComputeBoundry(LatLongPoint point, double halfSideInKm)
{
// Bounding box surrounding the point at given coordinates,
// assuming local approximation of Earth surface as a sphere
// of radius given by WGS84
var latitude = LocationHelper.DegreesToRadians(point.Latitude);
var longitude = LocationHelper.DegreesToRadians(point.Longitude);
var halfSide = 1000 * halfSideInKm;
// Radius of Earth at given latitude
var radius = WGS84EarthRadius(latitude);
// Radius of the parallel at given latitude
var pradius = radius * Math.Cos(latitude);
var latMin = latitude - halfSide / radius;
var latMax = latitude + halfSide / radius;
var lonMin = longitude - halfSide / pradius;
var lonMax = longitude + halfSide / pradius;
return(new LocationBoundry
{
NorthEast = new LatLongPoint
{
Latitude = LocationHelper.RadiansToDegrees(latMax),
Longitude = LocationHelper.RadiansToDegrees(lonMax)
},
SouthWest = new LatLongPoint
{
Latitude = LocationHelper.RadiansToDegrees(latMin),
Longitude = LocationHelper.RadiansToDegrees(lonMin)
}
});
}
