A digital orthophoto quadrangle (DOQ) is a
computer-generated image of an aerial photo. It has been
orthorectified--altered so that it has the geometric properties
of a map; DOQ's in fact meet National Map Accuracy
Standards. Thus the user can measure distances
accurately on a DOQ.
24,000-scale topographic map. Mosaicking is facilitated by
the fact that the images overlap. The DOQ's are
referenced to the North American Datum of 1983 and use
the Universal Transverse Mercator projection. Their
resolution is such that each pixel represents a square
meter.
The standard gray-scale DOQ includes an ASCII keyword
header followed by a series of 8-bit binary image lines. The
average file size for a black-and-white DOQ is 55
megabytes . Header information includes photographic
source type, date, production software, and date of the
digital elevation model metadata used in orthorectification.
Also, primary and secondary datum coordinates for the
upper left pixel are included to assist in referencing other
digital geospatial data. To view or manipulate one of these
images, the user must extract the header information from
the image and be equipped with editing software designed
to handle large image files.
A minority of the DOQ's are not gray scale, but
color-infrared, a false-color scheme used for certain
scientific and analytic purposes. These files average about
150 megabytes and are stored in band-interleaved-by-pixel,
or BIP, format.
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: Various.
Currentness_Reference: Publication date.
Status:
Progress: Complete
Maintenance_and_Update_Frequency: As needed
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -119.03487
East_Bounding_Coordinate: -112.22842
North_Bounding_Coordinate: 37.83482
South_Bounding_Coordinate: 32.49765
Keywords:
Theme:
Theme_Keyword_Thesaurus: Theme_Keyword_Thesaurus
Theme_Keyword: doqq
Theme_Keyword: doq
Theme_Keyword: digital orthophoto
Theme_Keyword: digital orthophotoquad
Theme_Keyword: digital image map
Theme_Keyword: aerial photograph
Theme_Keyword: quarter-quadrangle orthophoto
Access_Constraints: None
Use_Constraints: None
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Mr. Clarence Everly
Contact_Organization: Mojave Desert Ecosystem Program (MDEP)
Please request information by submitting a request via
email, fax or phone contact; you may also visit
www.mojavedata.gov, where you can make a map of the
Mojave to print or download in Adobe Acrobat PDF format,
access planimetric data and remotely sensed imagery, or
download geospatial data in ArcInfo export format.
Security_Information:
Security_Handling_Description: None
Security_Classification: Unclassified
Security_Classification_System: Unknown
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.
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: raster
Raster_Object_Information:
Raster_Object_Type: Pixel
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Universal_Transverse_Mercator:
UTM_Zone_Number: 11
Planar_Coordinate_Information:
Planar_Distance_Units: Meters
Geodetic_Model:
Horizontal_Datum_Name: NAD83 (WGS84)
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.
Please request information by submitting a request via
email, fax or phone contact; you may also visit
www.mojavedata.gov, where you can make a map of the
Mojave to print or download in Adobe Acrobat PDF format,
access planimetric data and remotely sensed imagery, or
download geospatial data in ArcInfo export format.
Metadata_Reference_Information:
Metadata_Date: 20010423
Metadata_Review_Date: 20010423
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Mojave Desert Ecosystem Program
Please request information by submitting a request via
email, fax or phone contact; you may also visit
www.mojavedata.gov, where you can make a map of the
Mojave to print or download in Adobe Acrobat PDF format,
access planimetric data and remotely sensed imagery, or
download geospatial data in ArcInfo export format.
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: Local time
Metadata_Access_Constraints: None
Metadata_Use_Constraints: None
Metadata_Security_Information:
Metadata_Security_Handling_Description: Unknown
Metadata_Security_Classification: Unclassified
Metadata_Security_Classification_System: None
Generated by mp version 2.7.8 on Tue May 01 11:33:09 2001