[sql] get distance lat-lng

calc_distance.sql

CREATE OR REPLACE FUNCTION calc_distance(
 pLat1 NUMBER,
 pLon1 NUMBER,
 pLat2 NUMBER,
 pLon2 NUMBER)
 RETURN NUMBER
IS

-- r is the spherical radius of earth in Kilometers 
cSpherRad CONSTANT NUMBER := 6367;
-- The spherical radius of earth in miles is 3956
a        NUMBER;
vLat     NUMBER;
vLat1Rad NUMBER;
vLat2Rad NUMBER;
vLon     NUMBER;
vLon1Rad NUMBER;
vLon2Rad NUMBER;

BEGIN
  /*
  Most computers require the arguments of trigonometric functions to be
  expressed in radians. To convert lon1, lat1 and lon2,lat2 from
  degrees,minutes, seconds to radians, first convert them to decimal
  degrees. To convert decimal degrees to radians, multiply the number
  of degrees by pi/180 = 0.017453293 radians/degrees.
  */

  vLat1Rad := pLat1 * 0.017453293;
  vLat2Rad := pLat2 * 0.017453293;
  vLon1Rad := pLon1 * 0.017453293;
  vLon2Rad := pLon2 * 0.017453293;

  vLon := vLon2Rad - vLon1Rad;
  vLat := vLat2Rad - vLat1Rad;

  a := POWER(SIN(vLat/2),2) + COS(vLat1Rad) * COS(vLat2Rad) * POWER(SIN(vLon/2),2);

  /*
  The intermediate result c is the great circle distance in radians.
  Inverse trigonometric functions return results expressed in radians.
  To express c in decimal degrees, multiply the number of radians by
   180/pi = 57.295780 degrees/radian.
  The great circle distance d will be in the same units as r.
  */

  RETURN ROUND(cSpherRad * 2 * ATAN2(SQRT(a), SQRT(1-a)),1);
EXCEPTION
  WHEN OTHERS THEN
    RETURN 999;
END;