code: def geo_distance(a, b):
      
      a_y = radians(a.y)
      b_y = radians(b.y)
      delta_x = radians(a.x - b.x)
      cos_x = (sin(a_y) * sin(b_y) +
               cos(a_y) * cos(b_y) * cos(delta_x))
      return acos(cos_x) * earth_radius_km
docs: Distance between two geo points in km. (p.x = long, p.y = lat)