Return offset in meters of second arg from first.

def MeterOffset((lat1, lon1), (lat2, lon2)):
    "Return offset in meters of second arg from first."
    dx = EarthDistance((lat1, lon1), (lat1, lon2))
    dy = EarthDistance((lat1, lon1), (lat2, lon1))
    if lat1 < lat2: dy *= -1
    if lon1 < lon2: dx *= -1
    return (dx, dy)