A 256x256 cell DEM for a region just southwest of Ann Arbor, Michigan was extracted from the Detroit-w USGS one degree DEM. Cells are square, just over 80 meters on a side. The terrain for this area is low relief, with minimum height of 222 meters and a maximum height of 320 meters. The average elevation is 271 meters with a standard deviation of 19 meters.
The grid-ascii representation of this file is 262,799 bytes in size. Gzipped, it is 25,255 bytes.
The dimensions of the DEM enable it to be decomposed hierarchically into non-overlapping blocks. The degree of decomposition, as with the test DEMs, depends on whether error in a block is greater than the user-specified tolerance. If it is, the block is divided.
The following table lists summary statistics for two decompositions,
both with q-level 4, but with different specified block tolerances.
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Below is the error map and blocking for the RMSE 2 map:
