U.S. Geological Survey, Unknown, Digital Orthophoto Quadrangles: U.S. Geological Survey, Reston, VA.
This is a raster data set. It contains the following raster data types:
Planar coordinates are encoded using row and column
Abscissae (x-coordinates) are specified to the nearest 1
Ordinates (y-coordinates) are specified to the nearest 1
Planar coordinates are specified in meters
The horizontal datum used is North American Datum 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.257.
DOQ's serve a variety of purposes, from interim maps to
field references for earth science investigations and
analysis. The DOQ is useful as a layer of a geographic
information system and as a tool for revision of digital
line graphs and topographic maps.
U.S. Geological Survey, Unknown, digital elevation model: U.S. Geological Survey, Reston, VA.
U.S. Geological Survey, Unknown, photo ID number: U.S. Geological Survey, Reston, VA.
U.S. Geological Survey, Unpublished material, project ground and photo control: U.S. Geological Survey, Reston, VA.
U.S. Geological Survey, Unpublished material, report of calibration: U.S. Geological Survey, Reston, VA.
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 quality manipulation.
Image brightness values may deviate from brightness values of
the original imagery due to image value interpolation during
the scanning and rectification processes.
Radiometry is verified by visual inspection of the digital
orthophoto quadrangle with the original unrectified image to
determine if the digital orthophoto has the same or better
image quality as the original unrectified input image.
Slight systematic radiometric differences can be detected
between adjacent DOQ files due primarily to differences in
source photography capture dates and sun angles of aerial
photography along flight lines. These differences can be
observed in an image's general lightness or darkness when
compared to adjacent DOQ file coverages.
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. The
vertical accuracy of the verified USGS format DEM is equivalent to or
better than a USGS level 1 or 2 DEM, with a root mean square error
(RMSE) of no greater than 7.0 meters. Field control is acquired by
third order class 1 or better survey methods sufficiently spaced to
meet National Map Accuracy Staandards (NMAS) 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.
All DOQ imagery is visually inspected for completeness to ensure that no
gaps, or image misplacement exist in the 3.75' image area or in overedge
coverage. DOQ images may be derived by mosaicking multiple images, in
order to insure complete coverage. All DOQ's are cloud free within the
3.75' image area. Some clouds may, very infrequently, be encountered only
in the overedge coverage. Source photography is leaf-off in deciduous
vegetation regions. Void areas having a radiometric value of zero and
appearing black may exist. These are areas for which no photographic
source is available or result from image transformation from other
planimetric systems to the Universal Transverse Mercator (UTM). 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
NDCDB.
All DOQ header data and image file sizes are validated by the Tape
Validation System (TVS) software prior to archiving in the National
Digital Cartographic Data Base (NDCDB). This validation procedure assures
correct physical format and field values for header record elements.
Logical relationships between header record elements are tested.
Are there legal restrictions on access or use of the data?
- Access_Constraints: None
- Use_Constraints:
None. Acknowledgement of the U.S. Geological Survey would be
appreciated in products derived from these data.
1-888-ASK-USGS (voice)
Digital Orthophotoquad
Although these data have been processed successfully on a computer
system at the U.S. Geological Survey no warranty expressed or
implied is made by the USGS regarding the utility of the data on any
other system, nor shall the act of distribution constitute any such
warranty. The USGS will warrant the delivery of this product in
computer-readable format and will offer appropriate adjustment
of credit when the product is determined unreadable by correctly
adjusted computer input peripherals, or when the physical medium
is delivered in damaged condition. Requests for adjustments of
credit must be made within 90 days from the date of this shipment
from the ordering site.
Data format: |
USGS uncompressed DOQ: The uncompressed USGS DOQ is a raw binary image file preceded by a metadata header record which consists of four 400-byte ACSII records, each blank padded to equal the length of a single line of image data. in format USGS_DOQ Size: 45 |
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Media you can order: |
8-mm helical-scan cartridge tape
(format Unlabelled, uncompressed Unix DD archive format. Standard block size: 30,270, but can be provided at 2,048 or multiples of 2,048. )
3480 cartridge tape (format Unlabelled, uncompressed Unix DD archive format. Blocksize = 6250 cpi. )
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The online copy of the data set (when available electronically) may be accessed without charge. For cartridge, cassette and CD-ROM the costs are available at: URL: <http://edc.usgs.gov/glis/hyper/order_info/prices#DOQ_QQUAD>
Data format: |
The USGS compressed DOQ is an IJG JPEG-compressed file. JPEG is a lossy compression technique. Unlike uncompressed DOQ's the compressed DOQ does not contain an attached header record as data compression corrupts ASCII text. A separate metadata file accompanies the compressed image file. The compressed data are distributed on CD-ROM, generally by county. However, some CD's may contain regions or partial counties and some counties may require multiple CD-ROM's. The presence of a DOQ in the NDCDB does not necessarily indicate the file is available on a compressed, county based CD-ROM. in format Compressed USGS DOQ in JPEG format. Size: 5 |
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Media you can order: |
CD-ROM
(format ISO 9660)
Note: This CD-ROM can be used with all computer operating systems that support CD-ROM as a logical storage device. All text files on this disc are in ASCII format. Data files are in ASCII or binary format.
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The cost for these CD-ROM products is available at: URL: <http://edc.usgs.gov/glis/hyper/order_info/prices#DOQ_COUNTY>
Dataset searching and ordering capabilities are available through the
Global Land Information System (GLIS) at:
URL: <http://edc.usgs.gov/webglis>
703 648 4543 (voice)