Indiana
Before attempting to use the IHAPI map, we strongly recommend that users read the instructions and view the associated IHAPI Video Tutorials.
Beginning in the 1930s, aerial surveys of Indiana counties were conducted about every 10 years; between the 1930s and the 1970s, more than 100,000 aerial photos of the state were taken. Copies of many of these black-and-white photos exist in archives of the Indiana Geological Survey, the Indiana State Archives, and various libraries and governmental agencies. A concise discussion of the uses of aerial photos can be found here.
Every historical aerial photograph has a unique identification number (ID) in its upper right corner. The date that the photo was taken appears in its upper left corner. Anyone interested in retrieving a particular photo from an archival collection must first determine its ID number.
For most counties, aerial surveys were conducted along north-south flight lines, although east-west flight lines were occasionally used. Along each flight line, photographs typically overlap by as much as 60 percent, so that overlapping pairs of photographs can be viewed stereoscopically. Adjacent flight lines also overlap.
For each survey, an index map of the county was assembled by stapling the individual photos together to create a mosaic. The mosaic, containing hundreds of individual photographs, was then re-photographed to create a large-format (typically 20 by 24 inch), low-resolution photomosaic index. In the past, you could obtain identification numbers of individual photos by physically visiting an archive and locating a site of interest on a paper copy of the photomosaic index. The appropriate individual aerial photo could then be retrieved from the archival collection. NOTE: The individual photos that are available from archival collections have resolutions that are much superior to that of corresponding photomosaics.
