public static List <Tuple <string, string> > GeohashQueries(Geolocation center, double radius)
{
GeopointService.ValidateGeopoint(center);
var queryBits = Math.Max(1, BoundingBoxBits(center, radius));
var geohashPrecision = queryBits / BITS_PER_CHAR;
var coordinates = BoundingBoxCoordinates(center, radius);
var queries = coordinates.Select((coordinate) =>
{
return(GeohashQuery(GeoHash.Encode(coordinate.Lat, coordinate.Lon, geohashPrecision), queryBits));
});
// remove duplicates
return(queries.ToHashSet().ToList());
}
public static double Distance(Geolocation point1, Geolocation point2)
{
GeopointService.ValidateGeopoint(point1);
GeopointService.ValidateGeopoint(point2);
var R = 6371e3; // metres
var φ1 = DegreesToRadians(point1.Latitude);
var φ2 = DegreesToRadians(point2.Latitude);
var Δφ = DegreesToRadians(point2.Latitude - point1.Latitude);
var Δλ = DegreesToRadians(point2.Longitude - point1.Longitude);
var a = Math.Sin(Δφ / 2) * Math.Sin(Δφ / 2) +
Math.Cos(φ1) * Math.Cos(φ2) *
Math.Sin(Δλ / 2) * Math.Sin(Δλ / 2);
var c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));
var d = R * c;
return(d);
}
