pysal.lib.cg.arcdist

pysal.lib.cg.arcdist(pt0, pt1, radius=6371.0)[source]

Arc distance between two points on a sphere.

Parameters:
pt0 : point

assumed to be in form (lng,lat)

pt1 : point

assumed to be in form (lng,lat)

radius : radius of the sphere

defaults to Earth’s radius

Source: http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html

Returns:
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