U.S. Geological Survey 2000 remote-sensing image ISGS GIS Database <quad_dir>/doq_utm15_83_<quadrant>.sid Champaign, IL Illinois State Geological Survey 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 derivative set of images to which this metadata file refers are cast on UTM Zone 15, NAD83. The geographic extent of the DOQ is equivalent to a quarter-quad plus the overedge, which ranges a minimum of 50 meters to a maximum of 300 meters beyond the extremes of the primary (NAD83) and secondary (NAD27) corner points. The overedge is included to facilitate tonal matching for mosaicking and for the placement of primary 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 standard, archived, USGS digital orthophoto is formatted as four ASCII header records, followed by a series of 8-bit binary image data records. The radiometric image brightness values are stored as 256 gray levels ranging from 0 to 255. The modified, compressed ISGS digital orthophoto is a black-and-white image in MrSID .sid format. The target compression ratio of 15:1 maintains sufficient detail for most mapping projects. The metadata provided in the doqindex.dbf table 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 data are stored in the ISGS GIS database by quadrangle. The path is *path_name_suppressed*/doq_utm15_83_<quadrant>.sid, where <letter> is the first letter of the quadrangle name, <quad_dir> is the quadrangle directory, and <quadrant> is either nw, ne, se, or sw. For example, the DOQ for the southwest quarter of the Columbia quadrangle is stored at *path_name_suppressed*/doq_utm15_83_sw.sid. 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. 1998 1999 ground condition complete irregular -91.5336 -87.2490 42.6108 36.8568 None DOQ DOQQ digital orthophoto digital orthophotoquad digital image map aerial photograph rectified photograph rectified image orthophoto quarter-quadrangle orthophoto 1-meter orthophoto 3.75- x 3.75-minute orthophoto 7.5- x 7.5-minute orthophoto MrSID image compression 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. US IL 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. FIPS code of State or Province 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. None None. For original, uncompressed DOQs (GeoTIFF format): 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. For modified, compressed DOQs (MrSID format): Image brightness and contrast has been enhanced for a more aesthetic and useful look since the original imagery was rather dark. This adjustment was conducted in image processing software, PCI. The resultant, modified image was compressed using MrSID at a target compression ratio of 15:1. MrSID is not lossless compression, however image degradation is only noticeable with extremely fine detail (i.e. plowing patterns in agricultural fields) when zoomed in to a level where the original imagery begins to pixelate. 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. Header data for each DOQ has been extracted and is available in the doqindex.dbf file. An explanation of each of the headings in doqindex.dbf file can be found in READMEDOQ.txt. 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 Standards (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 reliability 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. see RMSE in doqindex.dbf U.S. Bureau of the Budget, 1947, United States National Map Accuracy Standard. U.S. Geological Survey unknown map Reston, VA U.S. Geological Survey CD varies varies ground condition DEM1 Elevation data in the form of an ortho-DEM regridded to user-specified intervals and bounds. U.S. Geological Survey unknown remote-sensing image Reston, VA U.S. Geological Survey 40000 cartridge tape 1998 1999 ground condition PHOTO1 Panchromatic black and white NAPP photograph. NAPP photographs are centered on the DOQ coverage area. U.S. Geological Survey Unpublished material remote-sensing image Reston, VA U.S. Geological Survey various media various various ground condition CONTROL_INPUT Horizontal and vertical controls used to establish positions and elevations for reference and correlation purposes. U.S. Geological Survey Unpublished material remote-sensing image Reston, VA U.S. Geological Survey disk, paper various various Date of the camera calibration associated with the source photography CAMERA_INPUT Camera calibration parameters The production procedures, instrumentation, hardware and software used in the collection of standard USGS DOQ's vary depending on systems used at the contract, cooperator or USGS production sites. The majority of DOQ datasets are acquired through government contract. The process step describes, in general, the process used in the production of standard USGS DOQ data sets. Additional detail is included for the modifications made to the original, standard USGS DOQs for enhancement and online distribution through the ISGS. The rectification process requires, as input, a user parameter file to control the rectification process, a digital elevation model (DEM1) gridded to user specified bounds, projection, zone, datum and X-Y units, a scanned digital image file (PHOTO1) covering the same area as the DEM, ground X-Y-Z point values (CONTROL_INPUT) and their conjugate photo coordinates in the camera coordinate system, and measurements of the fiducial marks (CAMERA_INPUT) in the digitized image. The camera calibration report (CAMERA_INPUT) provides the focal length of the camera and the distances in millimeters from the camera's optical center to the camera's 8 fiducial marks. These marks define the frame of reference for spatial measurements made from the photograph. Ground control points (CONTROL_INPUT) acquired from ground surveys or developed in aerotriangulation, are third order class 1 or better, and meet National Map Accuracy Standard (NMAS) for 1:12,000-scale. Ground control points are in the Universal Transverse Mercator or the State Plane Coordinate System on NAD83. Horizontal and vertical residuals of aerotriangulated tie-points are equal to or less than 2.5 meters. Standard aerotriangulation passpoint configuration consists of 9 ground control points, one near each corner, one at the center near each side and 1 near the center of the photograph, are used. The conjugate positions of the ground control points on the photograph are measured and recorded in camera coordinates. The raster image file (PHOTO_1) is created by scanning an aerial photograph film diapositive with a precision image scanner. An aperture of approximately 25 to 32 microns is used, with an aperture no greater than 32 microns permitted. Using 1:40,000-scale photographs, a 25-micron scan aperture equates to a ground resolution of 1-meter. The scanner converts the photographic image densities to gray scale values ranging from 0 to 255 for black and white photographs. Scan files with ground resolution less than 1 meter or greater than 1 meter but less than 1.28 meters are resampled to 1 meter. The principal elevation data source (DEM1) are standard DEM datasets from the National Digital Cartographic Data Base (NDCDB). DEM's that meet USGS standards are also produced by contractors to fulfill DOQ production requirements and are subsequently archived in the NDCDB. All DEM data is equivalent to or better than USGS DEM standard level 1. The DEM used in the production of DOQ's generally has a 30-meter grid post spacing and possesses a vertical RMSE of 7-meters or less. A DEM covering the extent of the photograph is used for the rectification. The DEM is traversed from user- selected minimum to maximum X-Y values and centered on the DOQ coverage area. The DEM X-Y-Z values are used to find pixel coordinates in the digitized photograph using transformations mentioned above. For each raster image cell subdivision, a brightness or gray-scale value is obtained using nearest neighbor, bilinear, or cubic convolution resampling of the scanned image. The pixel processing algorithm is indicated in the header file. An inverse transformation relates the image coordinates referenced to the fiducial coordinate space back to scanner coordinate space. For those areas for which a 7.5-minute DEM is unavailable and relief differences are less than 150 feet, a planar-DEM (slope-plane substitute grid) may be used. Rectification Process: The photo control points and focal length are iteratively fitted to their conjugate ground control points using a single photo space resection equation. From this mathematical fit is obtained a rotation matrix of constants about the three axes of the camera. This rotation matrix can then be used to find the photograph or camera coordinates of any other ground X-Y-Z point. Next a two dimensional fit is made between the measured fiducial marks on the digitized photograph and their conjugate camera coordinates. Transformation constants are developed from the fit and the camera or photo coordinates are used in reverse to find their conjugate pixel coordinates on the digitized photograph. Quality Control: All data is inspected according to a quality control plan. DOQ contractors must meet DOQ standards for attribute accuracy, logical consistency, data completeness and horizontal positional accuracy. During the initial production phase, all rectification inputs and DOQ data sets are inspected for conformance to standards. After a production source demonstrates high quality, inspections will be made to 10% of delivery lots (40 DOQs per lot). All DOQ's are visually inspected for gross positional errors and tested for physical format standards. Post-processing by Illinois State Geological Survey: Upon receipt from the USGS, the DOQ imagery was initially checked for spatial integrity, image quality, and accurate associated header metadata. Each DOQ was imported into remote-sensing software, PCI, from PCI Geomatics, for brightening and increased contrast through the Normalization Enhancement function. The modified imagery was exported as a TIFF file with an accompanying TFW world file. This TIFF file was compressed using MrSID, image compression software from LizardTech, Inc. A target compression ratio of 15:1, intensity weight of 4 and a gamma of 2 were used in the compression. The resultant imagery has a ".sid" extension and the associated georeferenced world file has a ".swd" extension. MrSID minimizes image file size while retaining usability. Although compression results in a very slight distortion from the original image, degradation is not noticeable at a compression ratio of 15:1. For more information on MrSID and the wavelet compression used, visit www.lizardtech.com. Elements pertinent to individual DOQs were extracted from the DOQ header data and the MrSID output. These elements were placed in a dBASE file, doqindex.dbf. Additional metadata describing the elements in the doqindex.dbf file can be found in READMEDOQ.txt. DEM1, PHOTO1, CONTROL_INPUT, CAMERA_INPUT 2000 raster Pixel varies varies Universal Transverse Mercator 15 .09996 -93 0.0 500000. 0.0 row and column 1 1 meters North American Datum 1983 Geodetic Reference System 80 6378137 298.257 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 represented as a shade of gray varying from black to white. 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:*path_name_suppressed*/standards_doq.html> Softcopy in ASCII format is available at: <URL: ftp:*path_name_suppressed*/stdoqpt1.txt> <URL: ftp:*path_name_suppressed*/stdoqpt2.txt> Softcopy in WordPerfect format is available at: <URL: ftp:*path_name_suppressed*/stdoqpt1.wp5> <URL: ftp:*path_name_suppressed*/stdoqpt2.wp5> Softcopy in PostScript format is available at: <URL: ftp:*path_name_suppressed*/stdoqpt1.ps> <URL: ftp:*path_name_suppressed*/stdoqpt2.ps> Softcopy in hypertext is available at: <URL: ftp:*path_name_suppressed*/standards_doq.html> Illinois State Geological Survey Information Office mailing and physical address

615 East Peabody Drive

Champaign Illinois 61820 USA 217-333-4747 217-785-0211 217-244-0802 isgs@isgs.uiuc.edu 8:00 a.m. - 4:30 p.m., Monday-Friday, U.S. Central Time Digital Orthophoto Quadrangle. An MrSID .sid file is currently available free of charge at the Illinois Natural Resources Geospatial Data Clearinghouse. Refer to the Citation Information portion of this file for access to downloadable data and metadata. The Illinois Department of Natural Resources (DNR) provides these geographic data "as is." DNR makes no guarantee or warranty concerning the accuracy of information contained in the geographic data. DNR further makes no warranties, either expressed or implied as to any other matter whatsoever, including, without limitation, the condition of the product, or its fitness for any particular purpose. The burden for determining fitness for use lies entirely with the user. Although these data have been processed successfully on computers of DNR, no warranty, expressed or implied, is made by DNR regarding the use of these data on any other system, nor does the fact of distribution constitute or imply any such warranty. In no event shall the DNR have any liability whatsoever for payment of any consequential, incidental, indirect, special, or tort damages of any kind, including, but not limited to, any loss of profits arising out of use of or reliance on the geographic data or arising out of the delivery, installation, operation, or support by DNR. 20000502 Illinois State Geological Survey Information Office mailing and physical address

615 East Peabody Drive

Champaign Illinois 61820 USA 217-333-4747 217-785-0211 217-244-0802 isgs@isgs.uiuc.edu 8:00 a.m. - 4:30 p.m., Monday-Friday, U.S. Central Time Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 none none