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| GeoCommunity Mailing List |
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| Subject: | [gislist] SUM of "Area calculations" |
| Date: |
10/15/2003 12:50:01 PM |
| From: |
Eric Fevre |
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Dear list,
I submitted a question to the list at the end of September regarding
calculating the areas of parts of polygons overlapping buffer themes. The
original post is at the end of the message, and the respones I got follow.
1. Use the "Tabulate Areas" function of Spatial Analyst. You will need to
convert the land cover to a grid (use as small a cell size as you dare) and
merge all the buffers into one shape file. Then just select Analysis ->
Tabulate Areas. Use the land cover grid as the row theme and the buffers as
the column theme. (thanks to Cynthia True and Koukoulas Sotiris).
2. Jeff Jenness (http://www.jennessent.com) custom made me an extension
(!!!) to do just what I wanted - it looks at the polygons and points in the
view, draws circular buffers around the points (you choose the radius),
determines how much of the polygon of interest is inside or outside the
buffers, and gives you a table of the results - telling you how much of each
buffer is within or outside the polygon. Perfect! Thanks again Jeff.
Original post:
I'm working in Arcview 3.2a, with spatial analyst.
This is what I'm doing: I have a circular buffer zone around a point, and
this buffer zone overlaps another shapefile theme (eg a polygon denoting a
particular land cover class), and I want to work out how much of the area of
the land cover class theme is within the buffer.
What I normally do: I normally use the geoprocessing wizard to create a new
shapefile consisting of the area common to the two themes, then calculate
the area of the new shapefile. This works well.
What is the problem?: I need to do this for 750 separate buffer zones!!!
Is there a quicker/automatic way of carrying out this process? I don't
actually need a separate shapefile for the overlap areas, and a table that
just gives the areas would suffice.
I'll sum any answers I get, thanks to everyone in advance!
If replying directly, please delete the "SPAMREMOVE" section from my
address!
Thanks in advance.
Eric
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