code: def cprNL(lat):
      
  
      if lat == 0:
          return 59
  
      if lat == 87 or lat == -87:
          return 2
  
      if lat > 87 or lat < -87:
          return 1
  
      nz = 15
      a = 1 - np.cos(np.pi / (2 * nz))
      b = np.cos(np.pi / 180.0 * abs(lat)) ** 2
      nl = 2 * np.pi / (np.arccos(1 - a/b))
      NL = floor(nl)
      return NL
docs: NL() function in CPR decoding