Python Code for Calculating the Distance Between Two Points on the Earth

[webmast]

The following code snippet can be used to calculate the distance between two points.  It's a fairly decent algorithm using the Haversine Formula.  Enjoy!

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from math import *

#Insert some coordinates here
lat1 = 39.00
lon1 = -105.00
lat2 = 40.00
lon2 = -104.00
r = 3959.00 #mean radius of earth in miles

#This is the Haversine formula.  It is widely used for this purpose.
#In reality the earth is NOT a sphere so this formula can be off
#by a bit - usually less than .3% - not bad!

lat1_r,lon1_r,lat2_r,lon2_r = map(radians,(lat1,lon1,lat2,lon2))

dlon = lon2_r - lon1_r
dlat = lat2_r - lat1_r

a = sin(dlat/2)**2 + cos(lat1_r) * cos(lat2_r) * sin(dlon/2)**2
c = 2*atan2(sqrt(a),sqrt(1-a))
d = r*c

print """
Lat1: %f   Lon2: %f
Lon1: %f   Lat2: %f
Distance: %.2f miles
""" % (lat1,lat2,lon1,lon2,d)