Minecraft wiki entry for Mapping, associated text: Higher zoom-level maps can overlap one another because they can be crafted from zoom-level 0 maps that are centered only 128 blocks from each other. A zoom-level 1 map, for example, covers 256×256 blocks. So if you create a zoom-level 1 map from a zoom-level 0 map centered on (128,y,128)--which would cover a square bounded by the points (64,y,64)-(192,y,64)-(192,y,192)-(64,y,192)--the zoom-level 1 map will cover a square bounded by the points (0,y,0)-(256,y,0)-(256,y,256)-(0,y,256). The zoom-level 0 map adjacent (to the east) would be centered at (256,y,128) and described by the four points (192,y,64)-(320,y,64)-(320,y,192)-(192,y,192). A zoom-level 1 map crafted from this second zoom-level 0 map would be described by the points (128,y,0)-(384,y,0)-(384,y,256)-(128,y,256). The left half of this second zoom-level 1 map will overlap the right half of the first zoom-level 1 map. The illustration on the right may help.