haversine.py

frommathimportradians, cos, sin, asin, sqrt

defhaversine(lon1, lat1, lon2, lat2):
"""
 Calculate the great circle distance between two points 
 on the earth (specified in decimal degrees)
 """
# convert decimal degrees to radians 
lon1, lat1, lon2, lat2=map(radians, [lon1, lat1, lon2, lat2])

# haversine formula 
dlon=lon2-lon1
dlat=lat2-lat1
a=sin(dlat/2)**2+cos(lat1) *cos(lat2) *sin(dlon/2)**2
c=2*asin(sqrt(a)) 
r=6371# Radius of earth in kilometers. Use 3956 for miles
returnc*r