According to the resolution of the Original Image and the generated Image Pyramid, the program specifies the start layer and end layer of the Imagery Cache hierarchy (that is, the start value and end value of the hierarchy level number) from the first layer to the third layer.

According to the determined start hierarchy and end hierarchy, three hierarchical folders are established under the cache root directory. The name of the folder is the level number of the hierarchy. Therefore, the names of the three folders are 1, 2 and 3 respectively. As shown below, the second directory structure of the cache directory is established.