A digital

orthophoto An orthophoto, orthophotograph, orthoimage or orthoimagery is an aerial photograph or satellite imagery geometrically corrected ("orthorectified") such that the scale is uniform: the photo or image follows a given map projection. Unlike ...

quadrangle (DOQ) is

aerial photography Aerial photography (or airborne imagery) is the taking of photographs from an aircraft or other airborne platforms. When taking motion pictures, it is also known as aerial videography. Platforms for aerial photography include fixed-wing airc ...

or satellite imagery that has been corrected so that its

pixels In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the sm ...

are aligned with

longitude Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lette ...

and

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

lines, and have a narrowly defined region of coverage. This is a widely used format introduced by

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

(USGS). The correction technique is called image rectification and is a large part of photogrammetry. DOQs produced by the USGS cover an area measuring 7.5-minutes longitude by 7.5-minutes latitude (the same area covered by a USGS 1:24,000-scale

topographic map In modern mapping, a topographic map or topographic sheet is a type of map characterized by large- scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but histori ...

, also known as a 7.5-minute quadrangle) or 3.75-minutes by 3.75-minutes. The second format is also known as a digital orthophoto quarter quadrangle (DOQQ) because each covers one quarter of a quadrangle (four 1:12,000-scale DOQQs display the same area as one 1:24,000-scale DOQ).

References

External links

U.S. Geological Survey Mapping in the 20th Century: 1980’s - Digital Orthophoto Quadrangles

Birthplace of the DOQ — USGS Western Region

USGS GeoData Digital Orthophoto Quadrangles, Fact Sheet 057-01
Geographic information systems United States Geological Survey {{geodesy-stub

See also

References

External links