Based on the divided grouping grid for cache block data group storage, column folders for storing cache files are created in the row folders of the cache directory, that is, Create Folder under the row folder level in the cache directory, col column folders are created in each row folder, and the col calculation formula is as follows, that is, The number of columns in the divided grouping grid depends on the number of column folders created in each row folder under the corresponding hierarchical directory. Therefore, it is necessary to create two column folders under each row folder in the first layer. The name of the column folder in each row folder is the serial number of the column folder, starting from 0000 and increasing by 1 in turn. The serial number of the column folder actually corresponds to the column number of the grouping grid of the hierarchical block data; two column folders are created under each row folder in the second layer; four column folders are created under each row folder in the third layer. At this point, the fourth layer of the cache directory is constructed as follows:

Determination of the number of column folders in each row folder

The col _ image of the number of column folders under each line folder directory depends on the col _ setp of the grouping span of the number of columns after block processing in the current hierarchy, and the col _ setp of the grouping span of the number of columns is twice the row _ setp of the row grouping span. The specific calculation rules are as follows:

Where, n is the hierarchical level number of the current hierarchy; pow () is the power Exponential; col is the number of column folders to be created under the line folder. The name of the column folder is the serial number of the column folder, and the serial number starts from 0000 and increases in turn, such as 0001, 0002, 0003 … ; col _ image is the number of columns after image or Terrain Data block in the current layer; The col _ setp is the grouping span of the column number after the blocking processing in the current layering, the image or the subdivision grid generated after the Terrain Data blocking processing, on the basis of the row grouping, the blocking cache file corresponding to each col _ setp column in each row grouping is stored under a column folder directory, That is, after row grouping and column grouping, a grouping grid is constructed, and the cache files in the same grid of the grid will be placed in a column folder.