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Online Air Photo Indexes for County-based Sets
Box Folder for Statewide Sets
Aerial photography flown over Illinois before 1988 was created on a county-by-county basis. Each county’s flight was a separate project. Flight lines and photo numbers did not stay the same from one year’s flight to the next.
With the 1988 statewide set and the sets that followed, the flight line and photo pattern was unified and standardized. The flight line and photograph number assigned to an image for a location in 1988 will be also assigned for that location for the years that follow.
County-Based Sets (1935-1987)
When working with pre-1988 photographs, each year’s index for a county will need to be consulted. Project photo indexes are printed on separate sheets; a county might need as many as 6 or 8 sheets for complete coverage. Most of the indexes are photomosaic indexes; a complete set of photographs was arranged on a board, stapled into place, and then a photograph of the photographs was taken to create the index images. Some of the indexes are hand-drawn, schematic indexes. On the schematic indexes, flight lines usually appear at the edge of the map being used as the index’s base image and photo numbers appear at the approximate center point of the photographs. It is important to remember that county flight lines may be either east-west or north-south. There is no statewide standardization.
On the photomosaic indexes, because the indexes are photographs of the photos, the complete air photo identification is embedded in the image. The identification sequence is county (indicated by FIPS county code or USDA county code), flight line, and photo number. Photomosaic indexes, such as the sample above, do not include any place name labels, including city names or highway numbers. If indexes are being used in the Map Library, printed Illinois Department of Transportation county maps can be requested to help determine locations. If working with the online indexes, the Illinois Department of Transportation highway maps might be helpful. Scroll down on the page to the General Highway Maps section and click on County for a drop down pick list of Illinois counties.The maps available are zoomable and panable PDFs.
As they are hand-drawn, and usually not created by the air photo set producing agency, schematic indexes vary in style and method of information presentation. Schematic indexes often use county highway maps as their base map. On the schematic indexes, flight lines usually appear at the edge of the map being used as the index’s base image and photo numbers appear at the approximate center point of the photographs. Photo numbers may appear to be irregularly spaced because the schematic indexes reflect the completeness of the set being indexed.
Statewide Sets (1988- )
With the 1988 statewide set and the sets that followed, the flight line and photo pattern was unified and standardized; the same index is used for all 4 years. Flight lines for statewide sets always run north-south. One index book provides identification for photos from 1988, 1993, 1998, and 2005. When requesting photos from the statewide sets, please identify specific year(s) needed. The index for statewide sets flown between 1988 and 2005 is not available through the Digital Library but can be found in a Box folder.
There is a separate index for the natural color 2005 photos of the Chicago Metropolitan Area; it also is in the Illinois air photo Box folder.
If interested in photos from these sets, please read the READ ME file found in the Box folder first. Photos from the statewide set can be requested via an e-mail sent to the Map Library.