Tom's Blog

Thursday, March 5, 2009

Visualizing progress in the East Basin with GIS

What we are calling the East Basin is the final piece of land at Pleasant Valley Conservancy to be cleared. It is a 5 acre basin at the eastern end of the Conservancy. It faces south and southwest and slopes down from the level of the Ridge Prairie. In the 1937 air photo it was completely clear of trees, and was probably prairie remnant. Over the years it filled in completely with a mix of hardwood trees, including a large aspen clone.

In January 2008 a contractor cut all the invasive brush (mostly honeysuckle) and trees and various cooperators removed the wood for lumber or firewood. The aspens were girdled in May 2008, and should be dead in another year.

The photo above shows what the East Basin looked like after clearing (June 2008). The only trees remaining are the girdled aspens.

I have been using GIS a lot and have acquired several orthorectified air photos, the last being from 2005. Today, I discovered on that a 2008 ortho air photo was available. Wisconsin View is that great web site that gives anyone free access to ortho air photos from various counties in Wisconsin. I downloaded the 2008 photo for Dane County and brought it into ArcGIS. This was a huge file. Downloading took about a half hour and the final photo in Zip form was 828,300 KB.

The composite photo below compares the 2005 (lower) and the 2008 photo (upper). Not surprisingly, the East Basin is clear in the 2008 photo.


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