Comparing 32 bit and 16 bit elevation GeoPackages: Difference between revisions
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The tiled gridded coverage GeoPackage extension allows 32 bit source data to be converted to a GeoPackage with 16 bit integer tiles in PNG format, and still retain a significant number of decimals. This is accomplished by calculating a ''scale'' and ''offset'' for each tile, so that every tile utilizes the full space of the UInt16 data type (0- 65536). | The tiled gridded coverage GeoPackage extension allows 32 bit source data to be converted to a GeoPackage with 16 bit integer tiles in PNG format, and still retain a significant number of decimals. This is accomplished by calculating a ''scale'' and ''offset'' for each tile, so that every tile utilizes the full space of the UInt16 data type (0-65536). Each tile is converted from float32 to UInt16 as follows: | ||
<code>offset = min(tile) | <code> | ||
offset = min(tile) | |||
scale = (max(tile) - min(tile)) / (2^16 - 2) | |||
tile_png = (tile - offset) / scale | |||
</code> | |||
Revision as of 12:52, 14 June 2024
The tiled gridded coverage GeoPackage extension allows 32 bit source data to be converted to a GeoPackage with 16 bit integer tiles in PNG format, and still retain a significant number of decimals. This is accomplished by calculating a scale and offset for each tile, so that every tile utilizes the full space of the UInt16 data type (0-65536). Each tile is converted from float32 to UInt16 as follows:
offset = min(tile)
scale = (max(tile) - min(tile)) / (2^16 - 2)
tile_png = (tile - offset) / scale