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Polygon Contours

November 20 2009 | 0 comments
Categories: Cartographic Effects

The "Contour with Barriers" tool does not support polygon contours (yet). Can you suggest an easy work around for this feature?

Mapping Center Answer:

I suppose this is all in how you define "easy".

First, there is no simple automated way to do this.  If this is a one-off project, I would do this (and you'll need an ArcInfo and Spatial Analyst extension license):

1.  Produce contours

2.  Produce a reclassified DEM based on your contour interval, where each class is broken by a contour using the Reclassify tool.  For example if you have a 10 meter contour interval, you would reclassify the DEM using an equal interval classification starting at 0 with an interval of 10.

3.  Convert the reclassified DEM to polygons using the Raster to Polygon tool.  This might seem like what you want, but the edges will be stair-stepped along the raster cell edges.  Steps 4 & 5 address that.

4.  Convert the polygons to point (using option of the point always being inside the polygon) using the Feature to Point tool.

5.  Use the Feature to Polygon tool to create polygons based on your contours and the centroids.  This will use the much nicer geometry of the contours and assign the attributes of the points (elevation).   The one extra item you will need is an additional line that demarcates the area of interest extent.  That will allow complete polygons to be generated--you will have to add this manually to the contours data before using feature to polygon.




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