/* ******************************************************** */
/* The code for the GeoCodeCalc class was copied from here: */
/* http://pietschsoft.com/Blog/Post.aspx?PostID=1452        */
/* ******************************************************** */
var GeoCodeCalc = {};
GeoCodeCalc.EarthRadiusInMiles = 3956.0;
GeoCodeCalc.EarthRadiusInKilometers = 6367.0;

GeoCodeCalc.ToRadian = function(v) {
    return v * (Math.PI / 180);
};

GeoCodeCalc.DiffRadian = function(v1, v2) {
    return GeoCodeCalc.ToRadian(v2) - GeoCodeCalc.ToRadian(v1);
};

GeoCodeCalc.CalcDistance = function(lat1, lng1, lat2, lng2, radius) {
	if (radius == null)
	{
		radius = GeoCodeCalc.EarthRadiusInKilometers;
	}
	
    return radius * 2 * Math.asin(
            Math.min(1,
                Math.sqrt(
                    (
                        Math.pow(Math.sin((GeoCodeCalc.DiffRadian(lat1, lat2)) / 2.0), 2.0) +
                        Math.cos(GeoCodeCalc.ToRadian(lat1)) * Math.cos(GeoCodeCalc.ToRadian(lat2)) *
                        Math.pow(Math.sin((GeoCodeCalc.DiffRadian(lng1, lng2)) / 2.0), 2.0)
                    )
               )
           )
       );
};