Notes on where to find historical aerial imagery (thanks to Kass Green): The USDA has an archive of aerial imagery in Salt Lake City at APFOhttp://www.fsa.usda.gov/programs-and-services/aerial-photography/index. There is a ArcGIS online map of the tiles and dates of this photos. Search in ArcGIS online for the AFPO Historical Availability Tile Layer. USDA is in the process of scanning these photos, but you can order them through a manual process now (which can take a long time).
The EROS data center in Sioux Falls also has an archive of high altitude photos for the US from the 1980s. Also check out https://lta.cr.usgs.gov/NHAP and https://lta.cr.usgs.gov/NAPP . These photos are available digitally, but are not terrain corrected or georeferenced.
How many times has NAIP been acquired for California?
According to DFG, we have:
- NAIP 2014 aerial imagery, 1 m, 4 variations (natural color, 4-band, CIR/false color, NDVI)
- NAIP 2012 aerial imagery, 1 m, 4 variations (natural color, 4-band, CIR/false color, NDVI)
- NAIP 2010 aerial imagery, 1 m, 4 variations (natural color, 4-band, CIR/false color, NDVI)
- NAIP 2009 aerial imagery, 1 m, 4 variations (natural color, 4-band, CIR/false color, NDVI)
- NAIP 2005 aerial imagery, 1 m (natural color)
I was not aware the flight schedule was this frequent.
Still, I can't find a definitive information source that helps.
As part of the massive ongoing effort to map Sonoma County with high-res imagery and lidar, historic imagery of the county was collected and georeferenced. The Sonoma County Agricultural Preservation and Open Space District funded SFEI to mosaic 72 historic aerials taken over Sonoma County by the Department of Defense in 1942. Mark Tukman put together this web service with a image swiping tool showing the combination of the 2011 imagery service and the mosaiced historic imagery.
About the historic imagery: In 1942, the Department of War collected air photos in anticipation of a possible strike. These photos are the earliest complete image set for Sonoma County and give us an unprecedented look at Sonoma County's agriculture and open space prior to the post World War II baby boom.
These images are snaps from the service, both from an area outside Rohnert Park in Sonoma County: on the bottom is the image from 1942, on the top is the area in 2011 showing considerable development.