Metadata for Digital Orthophoto Quadrangles for Montana

Identification Information
Data Quality Information
Spatial Data Organization Information
Spatial Reference Information
Entity and Attribute Information
Distribution Information
Metadata Reference Information

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Identification Information:

Citation:

Originator: U.S. Geological Survey
Publication date: 2004
Title: Digital Orthophoto Quadrangles for Montana
Online linkage: http://apps.msl.mt.gov/Geographic_Information/Data/Aerial_Photos/doqq1.aspx

Browse graphic file name: http://docs.msl.mt.gov/geoinfo/Images/Metadata/doqq.jpg
Browse graphic file description: Thumbnail sample of monochrome DOQQ image

Browse graphic file name: ftp://ftp.geoinfo.msl.mt.gov/Documents/Maps/Individual/20041119_686_ortho_dates.gif
Browse graphic file description: Map of Montana showing photography dates

Abstract:

Orthophotos combine the image characteristics of a photograph with the geometric qualities of a map. The digital orthophoto quarter quadrangle images (DOQQ) created by the USGS are 1-meter ground resolution, quarter-quadrangle (3.75 minutes of latitude by 3.75 minutes of longitude) images cast on the Universal Transverse Mercator Projection (UTM) on the North American Datum of 1983 (NAD83).

The Montana State Library has modified these images to make them available on our web site. They are available as MrSID images, each covering an entire quadrangle. The entire state and Yellowstone National Park are avaialble in Montana State Plane NAD83 coordinates, and large parts of the state are also available in UTM NAD27 coordinates as MrSID images. All of these images are black-and-white, and they were produced from images taken between 1990 and 2003. An index file of the predominant image date for each quarter-quadrangle is available at ftp://ftp.geoinfo.msl.mt.gov/Data/Spatial/MSDI/Imagery/DOQQ_BW/doqq_index.zip.

Purpose:

DOQ's are useful in any application where aerial photographs are required, and they can be used to determine the geographic location of objects visible on the photos.

Time period of content:

Beginning date: 07/01/1990
Ending date: 09/29/2003
Currentness reference: ground condition

Status:

Progress: In work
Maintenance and update frequency: irregular

Access constraints: None

Use constraints:

The Montana State Library provides this product/service for informational purposes only. The Library did not produce it for, nor is it suitable for legal, engineering, or surveying purposes. Consumers of this information should review or consult the primary data and information sources to ascertain the viability of the information for their purposes. The Library provides these data in good faith but does not represent or warrant its accuracy, adequacy, or completeness. In no event shall the Library be liable for any incorrect results or analysis; any direct, indirect, special, or consequential damages to any party; or any lost profits arising out of or in connection with the use or the inability to use the data or the services provided. The Library makes these data and services available as a convenience to the public, and for no other purpose. The Library reserves the right to change or revise published data and/or services at any time.

Point of contact:

Montana State Library
P.O. Box 201800
Helena, Montana 59620-1800
Telephone: 406-444-5354
TDD/TTY telephone: 406-444-4799
Fax: 406-444-0266
E-Mail: geoinfo@mt.gov

Data Quality Information:

Attribute accuracy report:

When the State Library converted these images to State Plane Coordinates, the black pixels in several images in Northwest Montana were inadvertently coverted to white pixels. This is especially noticeable in lakes. Conversion of these images to State Plane Coordinates and to MrSID format caused some loss of sharpness from the original USGS images.

This is the Attribute Accuracy Report from the 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.

Completeness report:

The State Library has images for all of Montana's 11,758 quarter-quadrangles, and an additional 510 images in Yellowstone National Park and near the Idaho and Wyoming boundaries.

This is the Completeness Report from the U.S. Geological Survey:
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.

Horizontal Positional Accuracy Report:

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.

Lineage:

Source information:

Originator: U.S. Geological Survey
Title: digital elevation model
Source contribution:: This data was used to correct relief displacement in the aerial photos.
Beginning date: 1988
Ending date: 2004

Source information:

Originator: U.S. Geological Survey
Title: National Aerial Photography Program photographs
Source scale denominator: 40000
Source contribution:: Panchromatic black and white (or color infra-red) NAPP or NAPP-like photograph. NAPP photographs are centered on the DOQ coverage area.
Beginning date: 07/01/1990
Ending date: 09/24/2000

Process step:

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.

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 covering the same area as the DEM, ground X-Y-Z point values and their conjugate photo coordinates in the camera coordinate system, and measurements of the fiducial marks in the digitized image. The camera calibration report 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 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 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 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 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 coordiates 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.

Process step:

Make a full-quadrangle mosaic of four quarter-quadrangle images in UTM NAD27 coordinates and compress the image with MrSID. This was done with the MrSID encoder program from Lizard Tech. A UTM NAD27 world file was made for each image by reading the image header. We decided to make NAD27 images rather than NAD83 because these images could be overlaid with the original USGS Digital Raster Graphics images on our web site, which are also in UTM NAD27 coordinates. This is one of the three final products that are downloadable from our web site, and the result of this process step were not used in the subsequent ones. The Spatial_Reference_Information section of this metadata file does not apply to this product.

Process step:

Convert images to ESRI GRID format. Digital orthophoto images based on US Geological Survey DOQQ files were received by the State Library in various formats from various agencies. The library converted these images to ESRI GRID format so that they could be projected to State Plane coordinates. Where the image files still contained the USGS header data, these headers were used to create ESRI world files for the images so that they could be converted. Other images were received with world files and without headers. In these cases, the library relied on the supplied world files.

Process step:

Project the images to Montana State Plane Coordinates and convert them to TIFF format. When the images are projected, they become tilted and have triangular no-data background slivers added to their edges to make a rectangular image. We wanted these background areas to be white, but the projection software gave them a value of zero, or black. When we were processing our first batch of images, mostly in Northwest Montana, we converted all zero values to 255 to accomplish this. We did not discover until too late that the images had black pixels in them that we accidentally made white by doing this. For later batches of images, we assigned a value of one to any pixels with a value of zero before projecting them.

The result of this process step are the TIFF quarter-quadrangle images available on our web site.

Process step:

Make a full-quadrangle mosaic of four quarter-quadrangle images in Montana State Plane coordinates and compress the image with MrSID. This was done with the MrSID encoder program from Lizard Tech.

Spatial Data Organization Information:

Raster object information:

Raster object type: Pixel

Spatial Reference Information:

Horizontal coordinate system definition:

Grid coordinate system name: State Plane Coordinate System 1983

SPCS zone identifier: 2500

Lambert conformal conic:

Standard parallel: 45.00
Standard parallel: 49.00
Longitude of central meridian: -109.50
Latitude of projection origin: 44.25
False easting: 600000.0
False northing: 0.0

Planar distance units: meters

Geodetic model:

Horizontal datum name: North American Datum 1983
Ellipsoid name: Geodetic Reference System 80
Semi-major axis: 6378137
Denominator of flattening ratio: 298.257

Entity and Attribute Information:

Entity and attribute overview:: 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.
Entity and attribute detail citation:: U.S. Department of the Interior, U.S. Geological Survey, 1992,
Standards for digital orthophotos: Reston, VA.

Distribution Information:

Distributor:

Montana State Library
PO Box 201800
Helena, MT 59620-1800
Telephone: 406-444-5354
TDD/TTY telephone: 406-444-4799
Fax: 406-444-0266
E-Mail: geoinfo@mt.gov

Resource description: Downloadable Data

Distribution liability:

Standard order process:

Digital form:

Format name: MrSID
Online option:

Metadata Reference Information:

Metadata date: 01/10/2014

Metadata review date: 10/30/2013

Metadata review date: 04/17/2013

Metadata review date: 09/29/2004

Metadata review date: 07/07/2003

Metadata contact:

Montana State Library
PO Box 201800
Helena, Montana 59620-1800
Telephone: 406-444-5354
TDD/TTY telephone: 406-444-4799
Fax: 406-444-0266
E-Mail: geoinfo@mt.gov