libpysal.cg.arcdist¶

libpysal.cg.arcdist(pt0, pt1, radius=6371.0)[source]¶

Arc distance between two points on a sphere.

Parameters:

pt0tuple: A point assumed to be in form (longitude,latitude).
pt1tuple: A point assumed to be in form (longitude,latitude).
radiusfloat: The radius of a sphere. Default is Earth’s radius in kilometers, RADIUS_EARTH_KM (6371.0). Earth’s radius in miles, RADIUS_EARTH_MILES (3958.76) is also an option. Source: http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html

Returns:

distfloat: The arc distance between pt0 and pt1 using supplied radius.

Examples

>>> pt0 = (0, 0)
>>> pt1 = (180, 0)
>>> d = arcdist(pt0, pt1, RADIUS_EARTH_MILES)
>>> d == math.pi * RADIUS_EARTH_MILES
True