The National Geodetic Survey (NGS), formerly part of the U.S. Coast and Geodetic Survey, has been performing Aeronautical surveys since the 1920's. NGS, in accordance with a series of interagency agreements with the Federal Aviation Administration (FAA), provides airport geodetic control, runway, navigational aid, obstruction and other aeronautical data that is critical to the operation of the National Airspace System (NAS). The FAA uses the data to develop instrument approach and departure procedures, determine maximum takeoff weights, update aeronautical publications, and airport planning and engineering studies.Most of this data is source information obtained using field and photogrammetric survey methods. NGS acquires aerial photography of most commercial and many general aviation airports in the United States to support several types of aeronautical surveys, including Airport Obstruction Chart (AOC), Operational Evolution Plan (OEP), and Congressional (CGR) and, until recently, Area Navigation Approach (ANA). The high resolution photographs are used to perform a photogrammetric analysis of the Obstruction Identification Surface (OIS), determine areas obstructing the OIS, delineate aircraft movement areas and associated airport features, and are useful when performing ground surveys. Over 1,000 airports have been flown and photographs for these locations are currently available through the NGS photo library.