For example:
If a tile of LOD 21 is requested, but only tiles of up to LOD 20 are available, the corresponding quarter of the tile at LOD 20 should be cropped and returned.
If a tile of LOD 22 is requested in this example, the cropping should be done twice, recursively.
For example: If a tile of LOD 21 is requested, but only tiles of up to LOD 20 are available, the corresponding quarter of the tile at LOD 20 should be cropped and returned.
If a tile of LOD 22 is requested in this example, the cropping should be done twice, recursively.