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| Earth Resources Observation and Science (EROS) |
The National High Altitude Photography (NHAP) program, which was operated from 1980-1989, was coordinated by the U.S. Geological Survey as an interagency project to eliminate duplicate photography in various Government programs. The aim of the program was to cover the 48 conterminous states over a 5-year span. In the NHAP program, black-and-white and color-infrared aerial photographs were obtained on 9-inch film from an altitude of 40,000 feet above mean terrain elevation and are centered over USGS 7.5-minute quadrangles. The color-infrared photographs are at a scale of 1:58,000 (1 inch equals about .9 miles), and the black-and-white photographs are at a scale of 1:80,000 (1 inch equals about 1.26 miles). The NHAP program was designed to reduce Federal costs, eliminate duplication of effort, and to obtain complete, uniform coverage of the conterminous 48 states of the USA over a 5-year cycle. In 1987 the program name was changed to the National Aerial Photography Program (NAPP) in recognition of modifications in the user requirements and flight specifications.
While it was the intent of both the NHAP and NAPP programs to acquire complete coverage of the conterminous United States every five years, that has varied somewhat due to budgetary constraints. These programs provide nearly complete coverage of the entire United States on a fairly regular basis. NAPP coverage spans 1987 - 2003, with the current cycle from 1997 - 2003.
Flight season, film type, and coverage requirements are negotiated each year based upon available funds from the contributing federal and state agencies and the operational requirements of those agencies. (A list of contributing federal agencies is included in the Appendix.)
The NAPP/NHAP archive contains over 10,000 rolls of cartographic quality aerial photography acquired since 1980. On the average, 700 new rolls are acquired each year based upon a pre-determined flight schedule and season. Strict specifications regarding sun angle, cloud cover, minimal haze, stereoscopic coverage, and image inspection are followed. All photographs are cloud free, and only contract-acceptable photographs are indexed. The photographic frames are maintained as original and working master archives by two support facilities, the EROS Data Center and the U.S. Department of Agriculture's Aerial Photographic Field Office (APFO).
All photographs are manually assessed to ensure they meet the photographic, cartographic, coverage accuracy, and quality standards of each contract. Commercial flight contractors must meet a stringent list of acceptance criteria and provide proof of camera certification in order to fulfill contract requirements.
NHAP photography has a resolution of two meters.
The NHAP photography are indexed and supported by a data base that is maintained by the managing centers. User inquiries are answered through the use of EarthExplorer at: http://earthexplorer.cr.usgs.gov/
All NHAP photography can be searched and ordered through EarthExplorer at: http://earthexplorer.cr.usgs.gov/
Information about NHAP products and services can be found at: http://edc.usgs.gov/products/aerial/nhap.html
Applications and Related Data Sets
The NHAP/ NAPP archive is an invaluable source of high quality, cloud free, quad-based photography for the conterminous U.S. The photography can be integrated into Geographic Information Systems (GIS) as base images through high resolution scanners or they can be used to manually interpret land use, land cover, and feature changes when compared to other photography or satellite imagery acquired from earlier or later time periods.
The following Federal agencies have contributed funds to NHAP: U.S. Department of Agriculture (USDA) Farm Services Agency (FSA), formerly known as the Agricultural Stabilization and Conservation Service (ASCS), U.S. Forest Service (USFS), National Agricultural Statistics Service, National Resources Conservation Service (NRCS), previously known as Soil Conservation Service (SCS), and from the U.S. Department of Interior (DOI): Bureau of Land Management (BLM), U.S. Geological Survey (USGS). The Tennessee Valley Authority also contributed to this project.
Black-and-White Film Specifications
The black-and-white film emulsion shall be sensitive to red, green, and blue wave lengths (electromagnetic spectrum), and shall have an extended red sensitivity to approximately 720 to 750 manometer's. The film shall be exposed and processed to obtain a minimum density (D-min) of not less than 0.30 density units above base plus fog and a maximum (D-max) not in excess of 1.50 units above base plus fog. The aim point for density range is 1.0 density units for the average frame.
Color-Infrared Film Specifications
All color-infrared film shall be exposed and processed to the manufacturer's specifications. The CIR emulsion shall be sensitive to the visible and near infrared spectrum from 400 to 900 manometer's (electromagnetic spectrum).
Contract-Acceptable Flight Specifications
Flight specifications for the NHAP program require that all photographs meet certain standards regardless of the geographic area involved. The sun angle is thirty percent or higher to reduce potential shadow effects on the ground. Cloud cover must be absent, and atmospheric haze must be minimal. Even seasonal factors such as the presence of snow on the ground, flooding, or the amount of foliage are considered prior to accepting the photography. The center point of each photograph must also fall within a 1,000 foot radius of a pre-determined position within the north-south flight lines. Camera tilt shall not exceed four degrees, nor average more than two degrees, in any ten mile section of a flight, nor average more than one degree for the entire flight contract.
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