Aerial Photography
Aerial photographs are among the most important, widely available, and commonly utilized kinds of remotely sensed images. To learn more about the basics of aerial photography visit What is Aerial Photography?. You may also explore information about photogrammetry.
A good place to start your search for aerial photography is the Wisconsin Catalog of Aerial Photography, a comprehensive listing maintained by the State Cartographer's Office of aerial photography acquired by federal, state and local agencies and other groups. It generally includes medium-scale, vertical, stereoscopic photography used for mapping, resource inventories, and land use studies. Other sources of information are listed here. In addition, there is specific information about the National Aerial Photography Program's (NAPP) 1998 and 1999 Wisconsin surveys.
Orthophotography
Aerial photographs contain image displacements from the tilting of the camera and terrain relief; they are not of a uniform scale. This results in incorrect geometric measurements like area and distance. Orthophotographs are aerial photographs that have been corrected for displacement and processed to a (near) constant scale, allowing correct spatial measurements. The aerial photograph has in effect become a map. In digital form, often called a digital orthophotograph or DOP, it may be used as a map layer in a Geographic Information System. For more information, see our orthophotography page.
To find sources of orthophotography try OrthoFinder, a catalog of both federal and local sources of orthophotography in Wisconsin.
Satellite Imagery
We depend on satellite remote sensing for many aspects of Earth and planetary research in today's world. Learn about the history of remote sensing, present applications, and future remote sensing programs in What Is Remote Sensing? Also, learn about NASA's Landsat program, which was begun in 1972.
As remote sensing is used in an increasing number of applications, sources for satellite imagery have also increased. One can find available data from both public agencies and private companies.