A data processing method for sampling data from data each varying over time, each of the data being associated with each of grid points arranged in an area, the method includes: dividing the area into blocks; calculating a variation rate of each of the data associated with each of the grid points included in each of the blocks; dividing the blocks into sub-blocks in accordance with the variation rate of the blocks; calculating a variation rate of each set of the data associated with each of the grid points included in each of the sub-blocks; and determining a frequency of sampling data associated with each of the grid points for the sub-blocks of the blocks and for the rest of the blocks in accordance with the variation rate of the sub-blocks and the rest of the blocks.