A Digital Orthophoto Quadrangle (DOQ) is a computer-generated image of an aerial photograph in which the image displacement caused by terrain relief and camera tilt has been removed. The DOQ combines the image characteristics of the original photograph with the georeferenced qualities of a map.
DOQs are black and white (B/W), natural color, or color-infrared (CIR) images with 1-meter ground resolution.
The USGS produces three types of DOQs:
1. 3.75-minute (quarter-quad) DOQs cover an area measuring 3.75-minutes longitude by 3.75-minutes latitude. Most of the U.S. is currently available, and the remaining locations should be complete by 2004. Quarter-quad DOQs are available in both Native and GeoTIFF formats. Native format consists of an ASCII keyword header followed by a series of 8-bit binary image lines for B/W and 24-bit band-interleaved-by-pixel (BIP) for color. DOQs in native format are cast to the Universal Transverse Mercator (UTM) projection and referenced to either the North American Datum (NAD) of 1927 (NAD27) or the NAD of 1983 (NAD83). GeoTIFF format consists of a georeferenced Tagged Image File Format (TIFF), with all geographic referencing information embedded within the .tif file. DOQs in GeoTIFF format are cast to the UTM projection and referenced to NAD83. The average file size of a B/W quarter quad is 40-45 megabytes, and a color file is generally 140-150 megabytes. Quarter-quad DOQs are distributed via File Transfer Protocol (FTP) as uncompressed files.
2. 7.5-minute (full-quad) DOQs cover an area measuring 7.5-minutes longitude by 7.5-minutes latitude. Full-quad DOQs are mostly available for Oregon, Washington, and Alaska. Limited coverage may also be available for other states. Full-quad DOQs are available in both Native and GeoTIFF formats. Native is formatted with an ASCII keyword header followed by a series of 8-bit binary image lines for B/W. DOQs in native format are cast to the UTM projection and referenced to either NAD27 or NAD83. GeoTIFF is a georeferenced Tagged Image File Format with referencing information embedded within the .tif file. DOQs in GeoTIFF format are cast to the UTM projection and referenced to NAD83. The average file size of a B/W full quad is 140-150 megabytes. Full-quad DOQs are distributed via FTP as uncompressed files.
3. Seamless DOQs are available for free download from the Seamless site. DOQs on this site are the most current version and are available for the conterminous U.S.
[Summary provided by the USGS.]
Documentation information is not available for this collection.
Toggle Collection Information
Toggle Data Identification
During photographic reproduction of the source photography, limited
analog dodging is performed to improve image quality. Analog dodging
consists of holding back light from certain areas of the sensitized
photographic material to avoid overexposure. The diapositive is
inspected to insure clarity and radiometric uniformity. Diapositive
image brightness values are collected with a minimum of image
manipulation. Image brightness values may deviate from brightness
values of the original imagery due to image value interpolation
the scanning and rectification processes. Radiometry is verified by
visually inspecting the DOQs to the original unrectified image to
determine if the DOQ has the same image quality or better image
quality than the original unrectified input image. Slight systematic
and radiometric differences can be detected between adjacent DOQ
due primarily to differences in source photography capture dates and
Sun angles of aerial photography along flight lines. These
can be observed in an image's general lightness or darkness when
compared to adjacent DOQ file coverages.
Attribute_Accuracy_Value: 7.0 meters RMSE
The DOQ root-mean-square-error (RMSE) is the square root of the
average of the squared discrepancies. These discrepancies are the
differences in coordinate (x and y) values derived by comparing
the data being tested with values determined during
or by an independent survey of higher accuracy.
All DOQ header data and image file sizes are validated by Tape
Validation System (TVS) software prior to archiving in the Sales
Base. This validation procedure assures correct physical format and
field values for header record elements. Logical relationships
header record elements are tested.
All DOQ images are visually inspected for completeness to ensure
no gaps or image misplacement exists in the image area or in
coverage. The DOQ images may be derived by mosaicking multiple
in order to insure complete coverage. All DOQs are cloud free. Some
clouds may, very infrequently, be encountered only in the overedge
coverage. Source photography is leaf-off in deciduous vegetation
regions. Void areas may exist, having a radiometric value of zero
appearing black. These voids are areas for which no photographic
source is available or are the result of image transformation from
other planimetric systems to the UTM projection. In the latter case,
the void sliver areas are on the outside edges of the overedge area.
The data set field content of each DOQ header record element is
validated to assure completeness prior to archiving in the Sales
The DOQ horizontal positional accuracy and the assurance of that
accuracy depend, in part, on the accuracy of the data inputs to
the rectification process. These inputs consist of the digital
elevation model (DEM), aerotriangulation control and methods, the
photo source camera calibration, scanner calibration, and aerial
photographs that meet National Aerial Photography Program (NAPP)
standards. Field control is acquired by third order class 1 or
better survey methods sufficiently spaced to meet National Map
Accuracy Standards for 1:12,000-scale products. Aerial cameras
have current certification from the USGS, National Mapping
Division, Optical Science Laboratory. Test calibration scans are
performed on all source photography scanners.
The vertical accuracy of the verified USGS format DEM is equivalent
or better than a USGS level-1 or -2 DEM.
There is no guarantee of warranty concerning the accuracy of these data. Users should be aware that temporal changes may have occurred since the data was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of their limitations. Acknowledgement of the originating agencies would be appreciated in products derived from these data. Any user who modifies the data set is obligated to describe the types of modifications they perform. User specifically agrees not to misrepresent the data set, nor to imply that changes made were approved or endorsed by the U.S. Geological Survey. Please refer to http://www.usgs.gov/privacy.html for the USGS disclaimer.
Other Descriptive Keywords
Toggle Other Descriptive Keywords
DIGITAL IMAGE MAPS
7.5- x 7.5-MINUTE ORTHOPHOTOS
3.75- x 3.75-MINUTE ORTHOPHOTOS
ISO Topic Categories
IMAGERY/BASE MAPS/EARTH COVER
Toggle Acquisition Information
Toggle Temporal Information
Toggle Spatial Information
UNITED STATES OF AMERICA
Toggle Data Centers
Earth Resources Observation and Science Center, U.S. Geological Survey, U.S. Department of the Interior
This data center does not have any addresses listed.
This data center does not have any contact mechanisms listed.