Calculating percentage of one polygon that falls within the extent of another?

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12-17-2013 01:55 AM
MortimerTwist
New Contributor
I'm trying to calculate "landcover" ??? the percentage/proportion of various habitat types (Landcover shape file) that fall within the boundaries of various location buffers (a separate shape file).

I realize I can do this by clipping the landcover layer to each buffer and calculating the geometry/area of the habitat fields in the newly clipped landcover area layers to arrive at a proportion of cover for each buffer, but as I have over 550 buffers this would be incredibly time consuming.

Is there a more automated way I can achieve this?

Thank you
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2 Replies
RichardFairhurst
MVP Honored Contributor
I'm trying to calculate "landcover" �?? the percentage/proportion of various habitat types (Landcover shape file) that fall within the boundaries of various location buffers (a separate shape file).

I realize I can do this by clipping the landcover layer to each buffer and calculating the geometry/area of the habitat fields in the newly clipped landcover area layers to arrive at a proportion of cover for each buffer, but as I have over 550 buffers this would be incredibly time consuming.

Is there a more automated way I can achieve this?

Thank you


I would create a double field in each layer and calculate the area of the land covers and buffers into that field to make them a permanent value.  Then I would use the Intersect tool on both layers.  Then the Dissolve tool on the FIDs of the landcover and buffer polygons in the intersect as the unique case with the Max of the double field.  The percentage of each buffer for each land cover would be the current polygon area divided by the fixed double area for all dissolved polygon FIDs.
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MortimerTwist
New Contributor
Thanks for the reply. I got about halfway through then when I stumbled upon another method that worked as well, using the standalone program Geospatial Modelling Environment. There is a tool called isectpolyrast which does just this: calculates the amount of area (or proportion of area) of values in the raster that occupy the extent of the polygons. It worked like a charm for this and had the added bonus of writing the results as attributes in the original buffer shape file.
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