Center Geolocations

handy_geo.py

from math import cos, sin, asin, atan2, sqrt, radians, degrees

def _hsin(theta):
    return pow(sin(theta/2), 2)

def distance(lat1, lon1, lat2, lon2):
    """
    Calulates distance between two points set as 4 coordinates.
    """
    # convert to radians
    la1 = radians(lat1)
    lo1 = radians(lon1) 
    la2 = radians(lat2) 
    lo2 = radians(lon2)

    # must cast radius as float to multiply later
    r = 6378100.0 # Earth radius in meters.

    h = _hsin(la2-la1) + cos(la1)*cos(la2)*_hsin(lo2-lo1)

    return 2 * r * asin(sqrt(h))

def center_geolocation(geolocations):
    """
    Provide a relatively accurate center lat, lon returned as a list pair, given
    a list of list pairs.
    ex: in: geolocations = ((lat1,lon1), (lat2,lon2),)
        out: (center_lat, center_lon)
    """
    x = 0
    y = 0
    z = 0

    for lat, lon in geolocations:
        lat = float(radians(lat))
        lon = float(radians(lon))
        x += cos(lat) * cos(lon)
        y += cos(lat) * sin(lon)
        z += sin(lat)

    x = float(x / len(geolocations))
    y = float(y / len(geolocations))
    z = float(z / len(geolocations))

    return (degrees(atan2(z, sqrt(x * x + y * y))), degrees(atan2(y, x)))