About DNR Airphotos
As an aid to forest resource management, DNR Forestry acquires color infrared aerial photographs of forested counties on a rotating basis, covering each county about once every 8 years. Taken from 7900 feet above ground, the photos in their original form are highly detailed, showing individual trees, buildings and vehicles. Each covers an area slightly larger than four square miles. They are taken with 60% stereoscopic overlap for three-dimensional viewing. DNR airphotos appear predominantly red because they are taken with color infrared (CIR) film, which displays healthy vegetation in red rather than green tones. On CIR film, clear water usually looks black, turbid water looks blue, and paved surfaces are usually blue-gray. DNR photos are normally taken during fall, to capture leaf color changes that help distinguish vegetation types. Conifers (pines, spruces, firs) normally appear darker red than broadleaved trees.
High Resolution Digital Photos
When a new set of aerial photos is taken, we scan the resulting prints, which have a scale of 4 inches per mile, at the rate of 400 pixels per inch (or 300 pixels per inch for photos taken before 2002) to produce digital images. This captures a great deal of detail (each picture element measures just 1 square meter on the ground), but it creates a substantial 38-megabyte file. The low and medium resolution digital photos viewable free on Airphotos Online are reduced-resolution versions, made by a sampling process. These move rapidly over the Internet, but contain far less information than the originals.
DNR now makes a jpeg-compressed version of the original high resolution digital images available for download at $10 each, via a new online purchase page that accepts Visa and MasterCard. The compressed images are not visibly different from the uncompressed originals, and are used operationally within DNR. When you purchase a high resolution digital photo, it is added to a personal Airphotos Online Album created for you on our website, from which you can view it, print it, or download it to your own computer. Each image is a complete frame of photography, just as detailed as the sample above, but covering 15 times more area.
Any photo in your Album can be accessed again at any time.