Long Term Archive
2008 and 2010 images of the Hoover Dam
High resolution orthorectified images combine the image characteristics of an aerial photograph with the geometric qualities of a map. An orthoimage is a uniform-scale image where corrections have been made for feature displacement such as building tilt and for scale variations caused by terrain relief, sensor geometry, and camera tilt. A mathematical equation based on ground control points, sensor calibration information, and a digital elevation model is applied to each pixel to rectify the image to obtain the geometric qualities of a map.
A digital orthoimage may be created from several photographs mosaicked to form the final image. The source imagery may be black-and-white, natural color, or color infrared with a pixel resolution of 1-meter or finer. With orthoimagery, the resolution refers to the distance on the ground represented by each pixel.
Georeferenced orthoimages support a variety of geographic information analysis and mapping applications, and provide the foundation for most public and private Geographic Information Systems.
The High Resolution Orthoimagery collection has been acquired by the USGS through contracts, partnerships with other Federal, state, tribal, or regional agencies, and direct purchases from private industry vendors. Since data comes from a variety of sources, the resolution, area of coverage, file size, and projection will vary by dataset. The USGS EROS Center manages and distributes this orthoimagery, which includes black-and-white, natural color, color infrared, and color near-infrared. Digital download products are available in a Georeferenced Tagged Image File Format (GeoTIFF).
For information on how to cite USGS data plus guidance on usage restrictions,
please see our Data Citations and Use page at https://lta.cr.usgs.gov/citation.
Any use of trade, firm, or product names is for descriptive purposes only and
does not imply endorsement by the U.S. Government.
Long Term Archive User Services
U.S. Geological Survey (USGS)
Earth Resources Observation and Science (EROS) Center
47914 252nd Street
Sioux Falls, SD 57198-0001
Phone Number: 605-594-6151
Toll Free: 800-252-4547
Business Hours: Monday thru Friday, 8:00 a.m. to 4:00 p.m., Central Time