]> California Spatial Information Library &PRODUCTION_DATE; remote-sensing image Sacramento, CA State of California Orthophotos combine the image characteristics of a photograph with the geometric qualities of a map. The primary digital orthophotoquad (DOQ) is a 1-meter ground resolution, quarter-quadrangle (3.75-minutes of latitude by 3.75-minutes of longitude) image cast on the Universal Transverse Mercator Projection (UTM) on the North American Datum of 1983 (NAD83).The geographic extent of the DOQ is equivalent to a quarter-quad plus The overedge ranges a minimum of 50 meters to a maximum of 300 meters beyond the extremes of the primary and secondary corner points. The overedge is included to facilitate tonal matching for mosaicking and for the placement of the NAD83 and secondary datum corner ticks. The normal orientation of data is by lines (rows) and samples (columns). Each line contains a series of pixels ordered from west to east with the order of the lines from north to south. The radiometric image brightness values are stored as 256 gray levels ranging from 0 to 255. The metadata provided in the digital orthophoto contain a wide range of descriptive information including format source information, production instrumentation and dates, and data to assist with displaying and georeferencing the image. The standard distribution format of DOQs will be JPEG compressed images on CD-ROM by counties or special regions. The reconstituted image from the CD-ROM will exhibit some radiometric differences when compared to its uncompressed original but will retain the geometry of the uncompressed DOQ. Uncompressed DOQs are distributed on tape. The standard, archived digital orthophoto is formatted as four ASCII header records, followed by a series of 8-bit binary image data records. 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. These DOQ's have been made available thru the California Spatial Information Library URL:http://gis.ca.gov. They have been reformatted into GeoTIFF format, with a metadata an FGDC compliant metadata entry in the description tag. &earliest_image_date; &latest_image_date; ground condition In work irregular &westbc; &eastbc; &northbc; &southbc; None DOQ DOQQ digital orthophoto digital orthophotoquad digital image map aerial photograph rectified photograph rectified image orthophoto quarter-quadrangle orthophoto 1-meter orthophoto 2-meter orhtophoto 3.75- x 3.75-minute orthophoto 7.5- x 7.5-minute orthophoto U.S. Department of Commerce, 1977, Countries, dependencies, areas of special sovereignty, and their principal administrative divisions (Federal Information Processing Standard 10-3):Washington, D.C., National Institute of Standards and Technology. &NATION; U.S. Department of Commerce, 1987, Codes for the identification of the States, the District of Columbia and the outlying areas of The United States, and associated areas (Federal Information Processing Standard 5-2): Washington, D. C., National Institute of Standards and Technology. &STATE; U.S. Department of Commerce,1990, Counties and equivalent entities of The United States, its possessions, and associated areas (Federal Information Processing Standard 6-4): Washington, D.C. National Institute of Standards and Technology. FIPS code for county or counties. National Mapping Program, Orthophotomaps &QUADRANGLE_NAME; None None. Acknowledgement of the U.S. Geological Survey would be appreciated in products derived from these data. California Spatial Information Library mailing address

900 N. Street

Sacramento CA 916 653 9990 casil@gis.ca.gov CaSIL URL:http://gis.ca.gov/ is providing this dataset via an online option not offered by the U. S. Geological Survey. For information on the original distribution, see the coomplete list of Earth Science Information Centers at: <URL:http://www-nmd.usgs.gov/esic/esic_index.html> This dataset was created solely by the U.S. Geological Survey. CaSIL only reformatted the dataset for its use. Please acknowledge the U.S. Geological Survey for derived products from this dataset. U.S. Geological Survey &PRODUCTION_DATE; remote-sensing image Reston, VA U.S. Geological Survey 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. 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. 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. 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. Horizontal positional accuracy is determined by the Orthophoto Accuracy (ORACC) software program for DOQ data produced by the National Mapping Division. The program determines the accuracy by finding the line and sample coordinates of the passpoints in the DOQ and fitting these to their ground coordinates to develop a root mean square error (RMSE). From 4 to 9 points are checked. As a further accuracy test, the image line and sample coordinates of the DEM corners are transformed and compared with the actual X,Y DEM corner values to determine if they are within the RMSE. Additional information on this testing procedure can be found in U.S. Department of the Interior, U.S. Geological Survey, 1993, Technical Instructions, ORACC Users Manual (draft): Reston, VA. Adjacent DOQ's, when displayed together in a common planimetric coordinate system, may exhibit slight positional discrepancies across common DOQ boundaries. Linear features, such as streets, may not be continuous. These edge mismatches, however, still conform to positional horizontal accuracy within the NMAS. Field investigations to validate DOQ positional accuracy reliabilty are periodically conducted by the USGS, National Mapping Division, Geometronics Standards Section. DOQ's produced by cooperators and contractors use similarly approved RMSE test procedures. RMSE U.S.Bureau of the Budget, 1947, United States National Map Accuracy Standard. U.S. Geological Survey &PRODUCTION_DATE; remote-sensing image Reston, VA U.S. Geological Survey 12000 USGS Digital Orthophoto &earliest_image_date; &latest_image_date; ground condition DOQ The image data that was reformatted. The standard USGS Digital Orthophoto Quadrangle was reformatted into an GeoTiff file. The software used was GDAL, and libgeotiff, both available at URL:http://www.remotesensing.org/ DOQ 2002-06 For DOQ's from panchromatic source each pixel contains an 8-bit gray-scale value between 0-255. A value of 0 represents the color black while a value of 255 represents the color white. All values between 0 and 255 are repesented as a shade of gray varying from black to white. For color-infrared and natural color DOQs' a digital number from 0 to 255 will also be asssigned to each pixel but that number will refer to a color look-up table which will contain the RGB red, blue and green (RGB) values, each from 0 to 255, for that digital number. Areas where the rectification process is incomplete due to incomplete data (i.e., lack of elevation data, gaps), are represented with the numeric value of 0. U.S. Department of the Interior, U.S. Geological Survey, 1992, Standards for digital orthophotos: Reston, VA. A hypertext version is available at: <URL: ftp://www-nmd.usgs.gov/pub/doq_html/standards_doq.html> Softcopy in ASCII format is available at: <URL: ftp://www-nmd.usgs.gov/pub/ti/DOQ/doqstnds/stdoqpt1.txt> <URL: ftp://www-nmd.usgs.gov/pub/ti/DOQ/doqstnds/stdoqpt2.txt> Softcopy in WordPerfect format is available at: <URL: ftp://www-nmd.usgs.gov/pub/ti/DOQ/doqstnds/stdoqpt1.wp5> <URL: ftp://www-nmd.usgs.gov/pub/ti/DOQ/doqstnds/stdoqpt2.wp5> Softcopy in PostScript format is available at: <URL: ftp://www-nmd.usgs.gov/pub/ti/DOQ/doqstnds/stdoqpt1.ps> <URL: ftp://www-nmd.usgs.gov/pub/ti/DOQ/doqstnds/stdoqpt2.ps> Softcopy in hypertext is available at: <URL: ftp://www-nmd.usgs.gov/pub/doq_html/standards_doq.html> California Spatial Information Library mailing address

900 N. Street

Sacramento CA 916 653 9990 casil@gis.ca.gov CaSIL URL:http://gis.ca.gov/ is providing this dataset via an online option not offered by the U. S. Geological Survey. For information on the original distribution, see the coomplete list of Earth Science Information Centers at: <URL:http://www-nmd.usgs.gov/esic/esic_index.html> Digital Orthophotoquad Although these data have been processed successfully on a computer system at the U.S. Geological Survey, and further at the California Spatial Information Library, CaSIL, no warranty expressed or implied is made by the USGS or CaSIL regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. image/geotiff USGS DOQ image file stored as an extension to the TIFF file format to allow for geographic coordinate systems to be identified with the dataset. See URL:http://www.geotiff.org/ for more details. &networkr; The online copy of the data set (when available electronically) may be accessed without charge. 2002-06-01 California Spatial Information Library mailing address

900 N. Street

Sacramento CA 916 653 9990 casil@gis.ca.gov Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998