code: def calcOffset(self, x, y):
          
          # Datalayout
          # X = longitude
          # Y = latitude
          # Sample for size 1201x1201
          #  (   0/1200)     (   1/1200)  ...    (1199/1200)    (1200/1200)
          #  (   0/1199)     (   1/1199)  ...    (1199/1199)    (1200/1199)
          #       ...            ...                 ...             ...
          #  (   0/   1)     (   1/   1)  ...    (1199/   1)    (1200/   1)
          #  (   0/   0)     (   1/   0)  ...    (1199/   0)    (1200/   0)
          #  Some offsets:
          #  (0/1200)     0
          #  (1200/1200)  1200
          #  (0/1199)     1201
          #  (1200/1199)  2401
          #  (0/0)        1201*1200
          #  (1200/0)     1201*1201-1
          return x + self.size * (self.size - y - 1)
docs: Calculate offset into data array. Only uses to test correctness
              of the formula.