import math

def haversine(lat1, lon1, lat2, lon2):
"""
Compute and return range in km and bearing in degrees from lat1,lon1 to lat2,l
on2.
See http://www.movable-type.co.uk/scripts/latlong.html for details.
"""
R = 3396 # in km for Mars, approx
dLat = math.radians(lat2-lat1)
dLon = math.radians(lon2-lon1)
lat1 = math.radians(lat1)
lat2 = math.radians(lat2)

a = math.sin(dLat/2) * math.sin(dLat/2) + math.sin(dLon/2) * math.sin(dLon/2)
* math.cos(lat1) * math.cos(lat2)
c = 2 * math.atan2(math.sqrt(a), math.sqrt(1-a))
d = R * c

y = math.sin(dLon) * math.cos(lat2)
x = math.cos(lat1)*math.sin(lat2) - math.sin(lat1)*math.cos(lat2)*math.cos(dLo
n)
brng = math.degrees(math.atan2(y, x))

if brng<0: brng += 360

return d, brng