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Python code for getting the great circle distance between two lat/lon pairs from http://www.johndcook.com/python_longitude_latitude.html
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import math | |
def distance_on_unit_sphere(lat1, long1, lat2, long2): | |
# Convert latitude and longitude to | |
# spherical coordinates in radians. | |
degrees_to_radians = math.pi/180.0 | |
# phi = 90 - latitude | |
phi1 = (90.0 - lat1)*degrees_to_radians | |
phi2 = (90.0 - lat2)*degrees_to_radians | |
# theta = longitude | |
theta1 = long1*degrees_to_radians | |
theta2 = long2*degrees_to_radians | |
# Compute spherical distance from spherical coordinates. | |
# For two locations in spherical coordinates | |
# (1, theta, phi) and (1, theta, phi) | |
# cosine( arc length ) = | |
# sin phi sin phi' cos(theta-theta') + cos phi cos phi' | |
# distance = rho * arc length | |
cos = (math.sin(phi1)*math.sin(phi2)*math.cos(theta1 - theta2) + | |
math.cos(phi1)*math.cos(phi2)) | |
arc = math.acos( cos ) | |
# Remember to multiply arc by the radius of the earth | |
# in your favorite set of units to get length. | |
return arc |
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