Identification_Information:
  Citation:
    Citation_Information:
      Originator: U.S. Geologic Survey
      Publication_Date: Unknown
      Title:
        Digital Orthophoto quarter quadrangle, Unionville NW DOQQ


      Publication_Information:
        Publication_Place: Reston, VA
        Publisher: U.S. Geological Survey

      Other_Citation_Details:
      Online_Linkage:
        ftp://www.pasda.psu.edu/pub/pasda/doq/unionville_pa_nw.zip


      Larger_Work_Citation:
        Citation_Information:
          Originator: US Department of Commerce
          Publication_Date: 199310
          Title: TIGER/Line 1992
          Publication_Information:
            Publication_Place: Washington D.C.
            Publisher: Bureau of the Census

          Other_Citation_Details:
          Online_Linkage:
            http://www.pasda.psu.edu/ftp/doqlist.cgi






  Description:
    Abstract:
      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 standard, archived 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 metadata embedded 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.
      DOQQ's are distributed from PASDA as either Band-Interleaved by Line (BIL) or GeoTIFF as it was received from USGS with GeoTIFF being the newer format.
      As the set of DOQQ's available on PASDA nears completion all files will be converted to GeoTIFF.

    Purpose:
      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.

  Time_Period_of_Content:
    Time_Period_Information:
      Single_Date/Time:
        Calendar_Date:
          19920406


    Currentness_Reference:
      ground condition



  Status:
    Progress: On-going
    Maintenance_and_Update_Frequency: irregular

  Spatial_Domain:
    Bounding_Coordinates:
      West_Bounding_Coordinate: -75.75
      East_Bounding_Coordinate: -75.625
      North_Bounding_Coordinate: 40
      South_Bounding_Coordinate:
        39.875


  Keywords:
    Theme:
      Theme_Keyword_Thesaurus: none
      Theme_Keyword: DOQ
      Theme_Keyword: DOQQ
      Theme_Keyword: digital orthophoto
      Theme_Keyword: digital orthophotoquad
      Theme_Keyword: digital image map
      Theme_Keyword: aerial photograph
      Theme_Keyword: rectified photograph
      Theme_Keyword: rectified image
      Theme_Keyword: orthophoto
      Theme_Keyword: quarter-quadrangle orthophoto
      Theme_Keyword: 1-meter orthophoto
      Theme_Keyword: 3.75- x 3.75-minute orthophoto
      Theme_Keyword: 7.5- x 7.5-minute orthophoto

    Place:
      Place_Keyword_Thesaurus: none
      Place_Keyword:
        Unionville NW DOQQ


  Access_Constraints:
    None


  Use_Constraints:
    Acknowledgement of the U.S. Geological Survey would be appreciated in products derived from these data.


Data_Quality_Information:
  Attribute_Accuracy:
    Attribute_Accuracy_Report:
      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.

  Logical_Consistency_Report:
    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.

  Completeness_Report:
    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.

  Positional_Accuracy:
    Horizontal_Positional_Accuracy:
      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.

      Quantitative_Horizontal_Positional_Accuracy_Assessment:
        Horizontal_Positional_Accuracy_Value: RMSE
        Horizontal_Positional_Accuracy_Explanation:
          U.S.Bureau of the Budget, 1947, United States National Map
          Accuracy Standard.

  Lineage:
    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: U.S. Geological Survey
          Publication_Date: Unknown
          Title: digital elevation model
          Geospatial_Data_Presentation_Form: map
          Publication_Information:
            Publication_Place: Reston, VA
            Publisher:
              U.S. Geological Survey



      Type_of_Source_Media: cartridge tape
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Range_of_Dates/Times:
            Beginning_Date: 19920329
            Ending_Date:
              19950406


        Source_Currentness_Reference: ground condition

      Source_Citation_Abbreviation: DEM1
      Source_Contribution:
        Elevation data in the form of an ortho-DEM regridded
        to user-specified intervals and bounds.

    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: U.S. Geological Survey
          Publication_Date: Unknown
          Title: photo ID number
          Geospatial_Data_Presentation_Form: remote-sensing image
          Publication_Information:
            Publication_Place: Reston, VA
            Publisher:
              U.S. Geological Survey



      Source_Scale_Denominator: 40000
      Type_of_Source_Media: cartridge tape
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Range_of_Dates/Times:
            Beginning_Date: Unknown
            Ending_Date:
              Unknown


        Source_Currentness_Reference: ground condition

      Source_Citation_Abbreviation: PHOTO1
      Source_Contribution:
        Panchromatic black and white (or color infra-red)
        NAPP or NAPP-like photograph. NAPP photographs are
        centered on the DOQ coverage area.

    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: U.S. Geological Survey
          Publication_Date: Unknown
          Title: project ground and photo control
          Geospatial_Data_Presentation_Form: remote-sensing image
          Publication_Information:
            Publication_Place: Reston, VA
            Publisher:
              U.S. Geological Survey



      Type_of_Source_Media: various media
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Range_of_Dates/Times:
            Beginning_Date: Unknown
            Ending_Date:
              Unknown


        Source_Currentness_Reference: ground condition

      Source_Citation_Abbreviation: CONTROL_INPUT
      Source_Contribution:
        Horizontal and vertical control used
        to establish positions and elevations for reference and
        correlation purposes.

    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: U.S. Geological Survey
          Publication_Date: Unknown
          Title: report of calibration
          Geospatial_Data_Presentation_Form: remote-sensing image
          Publication_Information:
            Publication_Place: Reston, VA
            Publisher:
              U.S. Geological Survey



      Type_of_Source_Media: disc, paper
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Range_of_Dates/Times:
            Beginning_Date: Unknown
            Ending_Date:
              Unknown


        Source_Currentness_Reference: Date of the camera calibration associated with the source photography

      Source_Citation_Abbreviation: CAMERA_INPUT
      Source_Contribution: camera calibration parameters

    Process_Step:
      Process_Description:
        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 (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
        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
  Positional_Accuracy:
    Horizontal_Positional_Accuracy:
Spatial_Reference_Information:
  Horizontal_Coordinate_System_Definition:
    Planar:
      Grid_Coordinate_System:
        Grid_Coordinate_System_Name: Universal Transverse Mercator
        Universal_Transverse_Mercator:
          UTM_Zone_Number: 18
          Transverse_Mercator:
            Scale_Factor_at_Central_Meridian: 0.09996
            Longitude_of_Central_Meridian: -123.00
            Latitude_of_Projection_Origin: 0.0
            False_Easting: 500000.0
            False_Northing:
              0.0



      Planar_Coordinate_Information:
        Planar_Coordinate_Encoding_Method: row and column
        Coordinate_Representation:
          Abscissa_Resolution: 1
          Ordinate_Resolution: 1

        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:
  Overview_Description:
    Entity_and_Attribute_Overview:
      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.
    Entity_and_Attribute_Detail_Citation:
      U.S. Department of the Interior,  U.S. Geological Survey, 1992, Standards for digital orthophotos: Reston, VA.

      A hypertext version is available at:
      URL: http://mapping.usgs.gov/www/ti/DOQ/standards_doq.html

      Softcopy in WordPerfect format is available at:
      URL: ftp://mapping.usgs.gov/pub/ti/DOQ/doqstnds/doq1_12-96.wp6
      URL: ftp://mapping.usgs.gov/pub/ti/DOQ/doqstnds/doq2_12-96.wp6

      Softcopy in Portable Document Format (PDF) is available at:
      URL: ftp://mapping.usgs.gov/pub/ti/DOQ/doqstnds/usgsdoq.pd

Distribution_Information:
  Distributor:
    Contact_Information:
      Contact_Organization_Primary:
        Contact_Organization: Pennsylvania Spatial Data Access (PASDA)

      Contact_Address:
        Address_Type: mailing address
        Address: Land and Water Building
        City: University Park
        State_or_Province: PA
        Postal_Code: 16802
        Country: USA

      Contact_Electronic_Mail_Address:
        pasda@psu.edu



        <!DOCTYPE metadata SYSTEM 'metadata'>
  Distribution_Liability: The USER shall indemnify, save harmless, and, if requested, defend those parties involved with the development and distribution of this data, their officers, agents, and employees from and against any suits, claims, or actions for injury, death, or property damage arising out of the use of or any defect in the FILES or any accompanying documentation. Those parties involved with the development and distribution excluded any and all implied warranties, including warranties or merchantability and fitness for a particular purpose and makes no warranty or representation, either express or implied, with respect to the FILES or accompanying documentation, including its quality, performance, merchantability, or fitness for a particular purpose. The FILES and documentation are provided "as is" and the USER assumes the entire risk as to its quality and performance. Those parties involved with the development and distribution of this data will not be liable for any direct, indirect, special, incidental, or consequential damages arising out of the use or inability to use the FILES or any accompanying documentation.
  Standard_Order_Process:
    Digital_Form:
      Digital_Transfer_Information:
        Format_Name: Imagery, either GeoTIFF or band interleaved by line (BIL)
        File_Decompression_Technique: zip
        Format_Information_Content: Each DOQQ distribution file is comprised of two files; the image file, which has BIL or .TIF as the filename extension; and a header file, which has HDR or tfw as the filename extension.
        Transfer_Size: 35-45 MB

      Digital_Transfer_Option:
        Online_Option:
          Computer_Contact_Information:
            Network_Address:
              Network_Resource_Name:
                ftp://www.pasda.psu.edu/pub/pasda/doq/unionville_pa_nw.zip









Distribution_Information:
  Distributor:
    Contact_Information:
      Contact_Organization_Primary:
        Contact_Organization: Earth Science Information Center, U.S. Geological Survey

      Contact_Address:
        Address_Type: mailing address
        Address: Complete list of Earth Science Information Centers at: URL: http://mapping.usgs.gov/esic/esic_index.html

        Address: 507 National Center
        City: Reston
        State_or_Province: VA
        Postal_Code: 22092

      Contact_Voice_Telephone: 1 800 USA MAPS
      Hours_of_Service: 0800-1600
      Contact_Instructions:
        In addition to the address above there are  other ESIC offices throughout the country.  A full list of these offices is at: URL: http://mapping.usgs.gov/esic/esic_index.html



  Resource_Description: Digital Orthophotoquad
  Distribution_Liability: 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.
  Standard_Order_Process:
    Digital_Form:
      Digital_Transfer_Information:
        Format_Name: USGS_DOQ
        Format_Information_Content: 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.
        Transfer_Size: 45

      Digital_Transfer_Option:
        Offline_Option:
          Offline_Media: 8-mm helical-scan cartridge tape
          Recording_Format: Unlabelled, uncompressed Unix DD archive format. Standard block size: 30,270, but can be provided at 2,048 or multiples of 2,048.

        Offline_Option:
          Offline_Media: 3480 cartridge tape
          Recording_Format:
            Unlabelled, uncompressed Unix DD archive format. Blocksize = 6250 cpi.



    Fees:
      The online copy of the data set (when available electronically) may be accessed without charge. For 8-mm and 3480 cartridges the costs are:
      1 digital product = $40
      2 digital products = $60
      3 digital products = $80
      4 digital products = $100
      5 digital products = $120
      6 or more = $90 plus $7 per each product over six
      A $3.50 handling charge is applied to all mail orders.

  Standard_Order_Process:
    Digital_Form:
      Digital_Transfer_Information:
        Format_Name: Compressed USGS DOQ in JPEG format.
        Format_Information_Content: 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.
        File_Decompression_Technique: The algorithm employed by USGS for compressing DOQs is IJG JPEG, Version 4.0. This is a lossy compression using a standard Q or quality factor of 30.
        Transfer_Size: 5

      Digital_Transfer_Option:
        Offline_Option:
          Offline_Media: CD-ROM
          Recording_Format: ISO 9660
          Compatibility_Information:
            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.



    Fees:
      The charge is $32 per CD-ROM.  A $3.50 handling charge is applied to all mail orders.


Metadata_Reference_Information:
  Metadata_Date: 19961125
  Metadata_Review_Date:
    20000316

    <!DOCTYPE metadata SYSTEM 'metadata'>
  Metadata_Contact:
    Contact_Information:
      Contact_Organization_Primary:
        Contact_Organization: Pennsylvania Spatial Data Access (PASDA)
        Contact_Person: Christopher Pfeiffer

      Contact_Position: Metadata Coordinator
      Contact_Address:
        Address_Type: mailing address
        Address: 141 Land and Water Building
        City: University Park
        State_or_Province: PA
        Postal_Code: 16802
        Country: USA

      Contact_Voice_Telephone: 814-865-8792
      Contact_Facsimile_Telephone: 814-865-3378
      Contact_Electronic_Mail_Address:
        cxp7@psu.edu


  Metadata_Standard_Name: Content Standards for Digital Geospatial Metadata
  Metadata_Standard_Version: FGDC-STD-001-1998

