geodetic.py 文件源码

def est_dist(  latitude1,  longitude1,  latitude2,  longitude2 ) :
        """ 

        Returns an estimate of the distance between two geographic points
        This is a quick and dirty vinc_dist 
        which will generally estimate the distance to within 1%
        Returns distance in metres

        """
        f = 1.0 / 298.257223563     # WGS84
        a = 6378137.0           # metres

        piD4   = 0.785398163397 

        latitude1    = latitude1 * piD4 / 45.0
        longitude1 = longitude1 * piD4 / 45.0
        latitude2    = latitude2 * piD4 / 45.0
        longitude2 = longitude2 * piD4 / 45.0

        c = math.cos((latitude2+latitude1)/2.0)

        return math.sqrt( pow(math.fabs(latitude2-latitude1), 2) + \
                pow(math.fabs(longitude2-longitude1)*c, 2) ) * a * ( 1.0 - f + f * c )
   # END of rough estimate of the distance.