code: def _decdeg_distance(pt1, pt2):
      
  
      lat1, lon1 = pt1
      lat2, lon2 = pt2
  
      # Convert decimal degrees to radians
      lon1, lat1, lon2, lat2 = map(np.radians, [lon1, lat1, lon2, lat2])
  
      # haversine formula
      dlon = lon2 - lon1
      dlat = lat2 - lat1
      a = np.sin(dlat/2)**2 + np.cos(lat1) * np.cos(lat2) * np.sin(dlon/2)**2
      c = 2 * np.arcsin(np.sqrt(a))
      km = 6367 * c
  
      return km
docs: Earth surface distance (in km) between decimal latlong points using
      Haversine approximation.
  
      http://stackoverflow.com/questions/15736995/
      how-can-i-quickly-estimate-the-distance-between-two-latitude-longitude-
      points