Create row folders in the hierarchical folders of the cache directory based on the grouped grid for the grouped storage of the partitioned cache block data, that is, Create Folder under the hierarchical folder level in the cache directory, row row folders are to be created in each hierarchical folder, and the calculation formula of row is as follows. The number of line folders to be created is determined by the division result of the grouping grid. The number of line folders to be created under the corresponding hierarchical directory depends on the number of lines in the divided grouping grid. Therefore, it is necessary to create 2 line folders under the hierarchical folder of the first layer. The name of each line folder is the serial number of the line folder, starting from 0000 and increasing by 1 in turn. The serial number of the line folder actually corresponds to the line number of the grouping grid of the hierarchical block data; two line folders are created under the hierarchical folder of the second layer; four line folders are created under the hierarchical folder of the third layer. At this point, the third layer of the cache directory is constructed as follows:

The number of folders created in each hierarchical row is calculated as follows:

Where X is the intermediate variable; n is the level number of the current hierarchy; floor () is the round-down function; pow () is the power Exponential; Row is the number of row folders to be created under the current hierarchical directory. The name of the row folder is the serial number of the row folder, and the serial number starts from 0000 and increases in turn, such as 0001, 0002, 0003 … ; row _ image is the number of rows after image or Terrain Data block in the current layer; The row _ setp is the grouping span of the line number after the block processing in the current layering, that is, in the subdivision grid generated after the image or Terrain Data block processing, the block cache file corresponding to each row _ setp line of the grid is determined to be stored under a line folder directory, That is, each row of the grouping grid contains the block cache file of row _ setp rows, so the sequence number of the row folder can also be understood as the grouping grid row number.