Tom's Blog

Monday, October 24, 2011

New high resolution air photos available

New higher resolution air photos have been available in Wisconsin for a few months but I just got around to accessing them. The whole state of Wisconsin was "flown" in early spring 2010, in so-called "leaf off" conditions, at relatively high resolution. These images are available free, and because they are in GeoTIFF format, you don't need GIS to look at them (although they load into GIS without any effort). These photos were taken by the Wisconsin Regional Orthophotography Consortium (WROC), which is a partnership with state and local governments. (The air photography was done by Ayres Associates and Aero-Metrics.) These photos are completely in the public domain, and can be downloaded free of charge from the web site.

These air photos are at higher resolution than those created for agricultural purposes by the National Agriculture Imagery Program (NAIP). Although the NAIP photos, taken "leaf on", have advantages for ecological and restoration purposes, the WROC photos have some advantages since they permit much better view of cultural features (roads, trails, houses, parking lots, etc.).

When I first looked at the photos of Pleasant Valley, I got a real surprise. A rather large "funny black area" was visible covering the south-facing slope and the Crane and Valley Prairies. The interpretation is that our area was "flown" after our 23 March 2010 spring burn, but before our 29 March savanna burn. The black area where the burn took place really stood out. (The blacks of the north-facing woods areas are not caused by a burn, but simply by the dense forest.)
Don't be fooled by the low resolution of the photo here. I had to greatly reduce the resolution and size of the photo for use on my web site. The original GeoTIFF photo is of very high resolution and can be viewed equally well by the standard Windows XP photo viewer or by any photo editing program. However, be warned that these are large photos. Each of the two photos is over 500 MB in size!

To access these air photos, go to the web site and sign in. If you haven't accessed the site before you have to fill out a form, but there is no charge. Once signed in, go to the Aerial Photography page and then select WROC and Other Air Photos. Select your county and a map will come up overlaid with a grid that divides the county into Quarter Quads (based on the standard U.S.G.S. topographic quads). Once the selected photo is downloaded (it takes a bit of time), unzip it using the standard Windows Zip utility. You can use it either in GIS or with any photo editing software. Because Pleasant Valley Conservancy overlapped a NE and NW quad, I had to download two photos to cover the whole site. However, the two photos merged seamlessly in GIS.

These new high resolution air photos are extremely valuable for restoration purposes. You'll be surprised at the things you will learn!


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