Hawth's Analysis Tools for ArcGIS

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 Summary

EXTRACT RASTER EDGE TOOL
Input: a categorical (thematic) raster layer
Output: a line shapefile
Features:

  • creates a line shapefile representing "edges" between types in the thematic raster layer
  • each line is coded with the two types (raster values) on each side of the edge
  • all edge lines (arcs) representing the same type of edge are dissolved into a single line

Limitations:

  • ignores NoData cells in the raster
  • cannot be used with continuous raster layers


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 Example

Figures A & B. A thematic raster layer is processed to extract edges. Note that the edge lines shown in the second picture have been colour coded to demonstrate that the type of edge is coded in the attribute table (i.e. it is possible to distinguish between an edge between Type 1 and Type 2 versus Type 1 and Type 3). Also note that the edge lines are not smoothed - they follow the exact (square) edge of the raster cells.

 Help

Getting started. A thematic raster layer must be loaded into ArcMap in order to use this tool. Select the layer you wish to process from the drop-down box. Define an output line shapefile by pressing the folder button.

Multiple bands. This tool will process the first band from multi-band rasters. If your raster has more than one band and you wish to process a band that is not the first band, load only that band into the map. (When you press the Add Data button, navigate to the multi-band raster, and double-click that raster (this will show you each band as a separate layer as though the raster was a folder you had just opened). Select only the band you wish to process and add that to the map window. Then use this tool as described above.

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