Block coding. this extenls the run length encoding idea to two dimensions by using a series of square block to store data. figure 3.8a shows how the simple raster map of the happy vatiey forest has been subdivived a series of hierarchical square block, ten data block are required to store data about the forest These are seven will-cells. two four-cell squares and one nine-cell square, coordinates are required to locate the block in the raster matrix, in the example, the left-hand cellin a block is used as the locational for the block.