USGS High Resolution Orthoimage, Seattle / Tacoma, WA

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

Title: USGS High Resolution Orthoimage, Seattle / Tacoma, WA

Abstract: USGS High Resolution Orthoimage

Supplemental_Information:

1. How should this data set be cited?

   USGS (United States Geological Survey), 2003, USGS High Resolution Orthoimage, Seattle / Tacoma, WA: King County though USGS, King County, WA.

   Online Links:

   • None

   Other_Citation_Details:

   This data has been provided to King County through the USGS. The data is being made available through the King County GIS Center.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -122.05233309

   East_Bounding_Coordinate: -122.03790177

   North_Bounding_Coordinate: 47.60259646

   South_Bounding_Coordinate: 47.58876645

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 11-Jun-2002

   Ending_Date: 11-Jun-2002

   Currentness_Reference: Publication date

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: Raster Digital Data

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

   2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator

      Universal_Transverse_Mercator:

      UTM_Zone_Number: 10

      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.999600

      Longitude_of_Central_Meridian: -123.000000

      Latitude_of_Projection_Origin: 0.000000

      False_Easting: 500000.000000

      False_Northing: 0.000000

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 0.300000
      Ordinates (y-coordinates) are specified to the nearest 0.300000
      Planar coordinates are specified in Meters

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.
      

7. How does the data set describe geographic features?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • USGS (United States Geological Survey)

2. Who also contributed to the data set?

3. To whom should users address questions about the data?

   Triathlon
   Seattle, WA USA
   

   604-233-5000 (voice)
   604-233-5005 (FAX)
   

To produce colour orthoimagery of the Seattle/Tacoma Area

1. From what previous works were the data drawn?

   1192_6574_089 (source 1 of 4)

   Sensing, Selkirk Remote , 2002, USGS High Resolution Orthoimage, Seattle/Tacoma WA: USGS, Sioux Falls, SD.

   Type_of_Source_Media: Stable-base material

   Source_Scale_Denominator: 1:15,000

   Source_Contribution: Aerial photography used in orthorectification

   1193_6574_090 (source 2 of 4)

   Sensing, Selkirk Remote , 2002, USGS High Resolution Orthoimage, Seattle/Tacoma WA: USGS, Sioux Falls, SD.

   Type_of_Source_Media: Stable-base material

   Source_Scale_Denominator: 1:15,000

   Source_Contribution: Aerial photography used in orthorectification

   (source 3 of 4)

   Triathlon, 2002, DEM: Triathlon, Richmond, BC.

   Type_of_Source_Media: CD-ROM

   Source_Contribution: Digital Elevation Model used in the orthorectification process

   Field Control and ABGPS (source 4 of 4)

   Triathlon, 2002, Field control and ABGPS.

   Source_Contribution:

   ABGPS and ground control (i.e., horizontal/vertical, horizontal only and vertical only) were used in creating the project control

2. How were the data generated, processed, and modified?

   Date: 14-Feb-2003 (process 1 of 2)

   The horizontal accuracy of the orthorectified imagery is primarily determined by the quality of the Aerial Triangulation solution and the surface model (DEM). The AT process was initiated with the population of the Z/I project files with AGPS, ground survey, and project parameters which are prerequisite to initialization of ISAT. Upon completion of ISAT, a free-net adjustment was run to check for image blunders and poor image ties. Tie points were then corrected/added, ground control was measured, and the adjustment was run with the AGPS and ground control. QC of the adjustment was performed by withholding select ground control points. AT was finalized by densifying the control and performing relative and absolute orientations (RO and AO) for each model. The generation of the surface model was started with an ISAE test run of two models to establish and confirm the parameters for application to the automatic DEM modeling process. For this project, the software was instructed to model flat terrain and perform a high level of data smoothing. This ensured that the majority of the generated points modeled the actual terrain. Each stereo model was then reviewed, DEM points were edited and/or deleted, and breaklines were added, as required, to eliminate smearing and meet orthophoto accuracy standards. Orthorectifications were performed on only the core portion of each image in order to minimize inherent horizontal displacement that occurs radially from the photocenter. All orthophoto tiles were checked visually for relative horizontal accuracy in reference to adjacent tiles. Orthophoto measurements were taken for 41 horizontal ground control points in the project area. An RMSE was calculated for the XY error residuals of the positional differences between the surveyed values and the values measured from the rectified imagery.

   Person who carried out this activity:
   

   Doug Linwood
   Project Manager
   13800 Commerce Parkway
   Richmond, BC V6V 2J3
   Canada
   

   604-233-5009 (voice)
   604-233-5005 (FAX)
   dlinwood@triathloninc.com
   

   Hours_of_Service:

   Contact_Instructions:

   (process 2 of 2)

   King County reprojected the image files to WA State Plane North, NAD83/91 (HPGN) datum. The data was then retiled to the standard King County tiling scheme for raster data. The township-range tiles were compressed into JP2 format.

3. What similar or related data should the user be aware of?

1. How well have the observations been checked?

2. How accurate are the geographic locations?

   The relative accuracy was assembled by comparing adjacent rectified images. The absolute accuracy was assessed by measuring 41 of the ground control points in the rectified image against the actual surveyed co-ordinate position. The testing was for overall accuracy.

3. How accurate are the heights or depths?

4. Where are the gaps in the data? What is missing?

5. How consistent are the relationships among the observations, including topology?

Are there legal restrictions on access or use of the data?

Access_Constraints: None

Use_Constraints: None

1. Who distributes the data set? (Distributor 1 of 1)

   Michael Leathers
   King County GIS Center
   GIS Data Coordinator
   201 S. Jackson St
   Seattle, WA 98104
   USA
   

   206-263-4867 (voice)
   

   Hours_of_Service: Monday to Friday 9:00AM - 5:00PM

2. What's the catalog number I need to order this data set?

   tXXryy_02n098.jp2, where tXX refers to the PLSS township on which the tile scheme is based, and rYY indicates the range. _02 indicates the acquisition year is 2002, 'n' indicates natural color photography, with '098' representing 98/100ths foot (approximatly 1 ft) ground sample distance resolution (gsd).

3. What legal disclaimers am I supposed to read?

   King County disclaims any warranty of use of any digital product or data beyond that for which it was designed.

4. How can I download or order the data?

Dates:

Last modified:

Metadata author:

Michael Leathers
King County GIS Center
GIS Data Coordinator
201 S Jackson St
Seattle, WA 98104
USA

206-263-4867 (voice)
mike.leathers@metrokc.gov

Metadata standard:

FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)