This part of MIL's imagery collection is from the USGS National Aerial Photography Program (NAPP), which obtained cloud-free aerial photography of the conterminous United States between 1987 and 2007. NAPP photography was captured at a scale of 1:40,000, on 9-inch film, with each frame centered over quarters of USGS 7.5-minute quadrangles (or 1:24,000 scale topographic maps). The flight direction was north-to-south through each half of the 7.5-minute quads, and photographs were captured with 60% overlap to allow for stereographic viewing. The NAPP ocurred in three cycles, resulting in three photographs of most areas, each about five years apart during the 20 year period of the program.
The NAPP photography held by MIL covers most of California, though coverage varies for each of the three cycles. Most of the southern half of California is covered by all three sets of NAPP photography. The format of the majority of MIL's NAPP photography is positive transparencies, with black and white coverage for some areas, and color infrared for others (this varies depending on the cycle of the photography). Only pictorial coverage is available for most of the 2nd and 3rd cycle NAPP photography at MIL. In our catalog, the NAPP photography is divided into three Flight IDs based on the cycle: NAPP, NAPP-2C, and NAPP-3C.