National Agriculture Imagery Program (NAIP) Best Practice Report

A couple of days ago I stumbled across a report put together by ITT for the USDA's APFO group outlining suggestions for improving NAIP image quality. If you're interested in the radiometric processing of aerial photography, this is a must-read. The document outlines image collection guidelines (e.g. optimal flying conditions), the assessment of imagery quality, and image processing recommendations. Some of the material (e.g. orthorectification) is relatively high-level, but the sections on radiometry are great. Also be sure to check out the end of the document, which features a set of screen captures depicting radiometric problems and solutions (pre and post-processing) for image noise, sharpness, clipping, contrast, saturation, and color channel registration.

One thing to note is that NAIP imagery is generally available to the public. Aside from the USDA/NRCS Geospatial Data Gateway, it is also accessible from a number of regional/state-level organizations. A great resource for free orthophotos, NAIP and otherwise, is the World Wind Central section on the topic.

For some practical advice see Jarlath O'Neil-Dunne's recent post (and particularly the video) on the methodology and benefits of using the Vermont 2008 NAIP imagery in a GIS.