The Haversine formula in Firebird SQL => Calculate distance between two WGS84 Points

Hi,
I think might be helpful, today for a customer i do the Haversine formulas for Firebird Sql as a stored procedure.

This formula allow you to calculate the distance in meter between two WGS84 datum points(degree points of Earth).

You can call the procedure like this:

SELECT * FROM HAVERSINE_GENERIC(1, 45,474081, 9,179348, 45,456091, 9)

The result wil be aprox 14Km, the distance from my office and my house aprox.

the parameters of the procedure are:

    CORD_FORMAT integer,    --> 0 coordinate expressed in degree, 1 expressed in radiants
    LAT1  double precision, --> Latitude of Point1
    LOG1  double precision, --> Longitude of Point1
    LAT2  double precision, --> Latitude of Point2
    LOG2  double precision  --> Longitude of Point2

The procedure code is:

create procedure HAVERSINE_GENERIC (
    CORD_FORMAT integer,
    LAT1  double precision,
    LOG1  double precision,
    LAT2  double precision,
    LOG2  double precision)
returns (
    DISTANCE_METER  double precision)
as
declare variable RADIUS  double precision;
declare variable A  double precision;
declare variable A0  double precision;
declare variable A1  double precision;
declare variable A2  double precision;
declare variable DISTANCE_KM  double precision;
declare variable DLON  double precision;
declare variable DLAT  double precision;
begin
  /* LE COORDINATE IN INGRESSO DOVRANNO ESSERE ESPRESSE IN RADIANTI */
  if (CORD_FORMAT = 1) then
   BEGIN
    LAT1 = LAT1 * (pi()/180);
    LOG1 = LOG1 * (pi()/180);
    LAT2 = LAT2 * (pi()/180);
    LOG2 = LOG2 * (pi()/180);
   END
  /* RAGGIO DELLA TERRA IN KM  */
  radius=6378.137;



  dlon= (loG2-loG1);
  dlat= (lat2-lat1);

  a1 = (sin(dlat/2));
  a1 = a1 * a1;
  a2 = (sin(dlon/2));
  a2 = a2 * a2;

  a=  a1 + cos(lat1)*cos(lat2)*a2;

  distance_km= radius*(2*atan2(sqrt(a),sqrt(1-a)));

  distance_meter = distance_km*1000;


  suspend;
end