NAIP horizontal accuracy specifications - From 2003 to 2004 the specifications were as follows: 1-meter Ground Sample Distance (GSD) imagery was to match within 3-meters, and 2-meter GSD to match within 20 meters of reference imagery. For 2005 the 1-meter GSD specification was changed to 5 meters matching to reference imagery. In 2006, all states used the same specifications as 2005 except for Utah, which required a match of +/- 6 meters to true ground. In 2007, all specifications were the same as 2006, except for Arizona, which used true ground specifications. In 2008 approximately half of the states acquired used true ground specifications and the other half used reference imagery. The 2008 states that used absolute ground control where; Indiana, Minnesota, New Hampshire, North Carolina, Texas, Vermont, and Virginia. From 2009 to present all NAIP imagery acquisitions used the +/- 6 meters to ground specification.
NAIP utilized film cameras until 2010, when 4 band acquisition became standard. From 2003 – 2009 NAIP was acquired with both film and digital cameras. NAIP photographs acquired with a film camera have a nominal scale of 1:40,000. Most digital NAIP acquisition has 4 band, utilizing two main types of digital cameras – DMC (Intergraph) and ADS (Leica). See the APFO website for more details.
Color balancing is applied to the Compressed County Mosaics(CCM). Color balancing adjusts the intensity of colors within each image to match adjacent images. Non color-balanced quarter quad images are available from APFO. NAIP is orthorectified using the National Elevation Dataset (NED). Orthorectification corrects the scale of the image, using a 3D model of the earth.
