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Technical Article   FAQ:  Why does the data bit depth increase when a raster is projected, rotated, or clipped?

Article ID: 28470
Software:  ArcGIS - ArcEditor 8.1, 8.1.2, 8.2, 8.3, 9.0, 9.1, 9.2, 9.3, 9.3.1, 10 ArcGIS - ArcInfo 8.0.1, 8.0.2, 8.1, 8.1.2, 8.2, 8.3, 9.0, 9.1, 9.2, 9.3, 9.3.1, 10 ArcGIS - ArcView 8.1, 8.1.2, 8.2, 8.3, 9.0, 9.1, 9.2
Platforms: N/A

Question

Why does the data bit depth increase when a raster is projected, rotated, or clipped?

Answer

Pixel depth is increased to provide the space to store 'nodata' values. This allows changes, such as a shift or a mask, to be applied to the raster. Pixels within the new raster's bounding extent may need to be assigned as nodata to preserve data values and also keep a proper extent.

For example, values range from 0-255 in an 8-bit raster. If a nodata value is introduced, the bit depth must increased to 16-bit to store the nodata value, which would be the 257th value.

Related Information


Created: 1/5/2005
Last Modified: 1/20/2012

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