Remote Sensing Technologies

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Test Site Catalog

Geometry Sites Resources

The geometric characterization involves understanding the processes by which pixel coordinates within an image can be mapped to known locations on the ground. Generally, this involves the use of well-surveyed, photo-identifiable targets placed within a scene. Geometry test sites are core to any Quality Assurance/Quality Control (QA/QC) strategy. These sites can be useful for evaluating geodetic accuracy of sensors.

Utilizing USGS Test Ranges for Accuracy Assessments

The USGS EROS has established three ranges that are suitable for use in the assessment of aerial and satellite imagery for their geometric and geodetic accuracy.  These ranges are located in and around the cities of Sioux Falls, South Dakota, Pueblo, Colorado, and Rolla Missouri.  Their locations are shown in the Google Earth image below.

These ranges were initially placed as the first three ranges of a series of ranges intended to be spread across the contiguous United States for an USGS-led aerial imagery quality assurance program that was then canceled.  At this time (2014) there are no firm plans to establish additional ranges.

Information about each of the three ranges is available online in the USGS Test Site Catalog (http://calval.cr.usgs.gov/rst-resources/sites_catalog/geometric-sites/).

The extent of each range varies in size with the Rolla, MO range being the smallest and the Sioux Falls range being the largest with the Pueblo range being close behind.  The Rolla range is approximately 2.5 mi x 2.5 miles in extent, making it primarily suitable for use in aerial imaging.   The larger areal extent of the Sioux Falls or Pueblo ranges makes them suitable for up to ~60km swath width satellite imagery.

Within each range, control points have been surveyed using GPS surveying equipment, typically to an accuracy of 2cm or less.  Generally, control points were chosen from existing features that can be readily identified in overhead imagery. These include the intersections of sidewalks, pavement, etc.  Occasionally, painted targets have been used.  Examples of both are shown below:

control_points

The survey points should be suitable for use in measuring the accuracy of imagery as fine as 3” (7.5cm) ground sample distance (GSD).  Surveyed latitude, longitude, and altitude measurements are available for each control point, as well as pictures such as those above, are available to assist in point identification and to provide context for each point.

To properly measure the accuracy of any geospatial imagery, users should follow established guidelines such as those established by the Federal Geographic Data Committee (FGDC), in particular the Geospatial Positioning Accuracy Standards, Part 3 (FGDC-STD-007.3-1998)  These can be found at:  http://www.fgdc.gov/standards/standards_publications/

These ranges and the control information within them are used by the USGS to assess the quality of remotely sensed imagery.  As such, the information is sensitive and distribution is limited.  To request control point information, including the supporting information described above, please contact the USGS Project Manager, Greg Stensaas, at the contact information below:

Greg Stensaas, RST Project Manager
USGS EROS Science Center
47194 252nd St
Sioux Falls, SD  57198
Tele: (605)594-2569
E-mail: stensaas@usgs.gov

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URL: Remote Sensing Technology
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Page Last Modified: January 8, 2013