Geodetic Control in Wisconsin
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Geodetic Control in Wisconsin
- 1. Geodetic Control in Wisconsin Wisconsin Land Information Association La Crosse, Wisconsin May 17, 2011 John Ellingson Wisconsin State Geodetic Advisor john.ellingson@noaa.gov , cell 202-306-6904
- 2. NGS Mission Statement To define, maintain and provide access to the National Spatial Reference System (NSRS) to meet our nation’s economic, social, and environmental needs.
- 4. Geodetic Datum is a reference system from which measurements are made Examples: NAD 27, NAD 83, WGS 84, ITRF Adjustment is a mathematical process of adjusting observed positions based on standard (control) positions Ex: NAD 83(1986), NAD 83(1991), NAD 83(1997), NAD 83(2007), NAD 83(2011)
- 5. Constancy of Position vs. Accuracy of Position Consistent coordinate systems have existed for essentially 200 years The accuracy has continually improved
- 7. HORIZONTAL SHIFTS From NAD 27……..to NAD 83
- 8. Quick Demo: Obtaining Geodetic Control……Using NGS’ DSWorld software with Google Earth
- 9. Horizontal changes Example: Station “Kollath” (PID NH1578), Dane County Southwest of Madison
- 10. NGS CORS map http://www.ngs.noaa.gov/CORS/GoogleMap/CORS.shtml
- 11. Reasons for the new Multi-Year CORS Solution - Public release in July 2011 Info at => http://beta.ngs.noaa.gov/myear/
- 14. “DSWorld” - Open the NGS main page at www.ngs.noaa.gov Roll Pointer over “TOOLS” button “DOWNLOAD PC SOFTWARE”
- 15. Click on: User Contributed Software
- 16. click on DSWORLD (Version *.**)
- 17. DSWorld Installation Tip Hint: Save the “DSWorldV210.zip” download file in a folder that is within two directories of your C: drive prompt…. Examples: C:SWorldSWorldV210.zip or C:olderSWorldSWorldV210.zip
- 18. Download “GOOGLE EARTH” at : http://earth.google.com/download-earth.html Click here
Editor's Notes
- The National Spatial Reference System is a consistent coordinate system that defines latitude, longitude, height, scale, gravity, and orientation throughout the United States. Originally part of the Coast and Geodetic Survey, this mission arose from a need for accurate positions for nautical charts to improve coastal commerce. Geodetic control monuments, often brass disks, have traditionally been constructed and then measured to provide locations and/or elevations. As technology has improved, moved away from passive controls to continuously operating stations (shown as red symbols). Continued maintenance and improvement is vital to providing accurate information, including flood mapping and inundation models, subsequent to earthquake activity, and coast areas, habitat restoration planning.
- NGS is mandated to define the datums for the United States. A datum is a set of constants specifying the coordinate system used for geodetic control, which is part of the NSRS. This datum is used for all federal civil mapping, but is available for public and private use. The challenge is to adapt the system following technological improvements, such as utilization of GPS surveying procedures.The current horizontal datum is the North American Datum 1983 and the current vertical datum is the North American Vertical Datum 1988.