Geodetic Control in Wisconsin


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  • 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.
  • Geodetic Control in Wisconsin

    1. 1. Geodetic Control<br /> in Wisconsin<br />Wisconsin Land Information Association<br />La Crosse, Wisconsin<br />May 17, 2011<br />John Ellingson<br />Wisconsin State Geodetic Advisor<br /> , cell 202-306-6904<br />
    2. 2. NGS Mission Statement<br />To define, maintain and provide access to the National Spatial Reference System (NSRS) to meet our nation’s economic, social, and environmental needs.<br />
    3. 3. Geodetic Datums<br />NGS is mandated to define the datums for the United States<br />Definition of a Datum: A set of constants specifying the coordinate system used for geodetic control<br />Part of the National Spatial Reference System (NSRS)<br />For all federal civil mapping<br />Challenge to update due to technological improvements<br /><ul><li>Current horizontal datum: NAD 83</li></ul>North American Datum of 1983<br /><ul><li>Current vertical datum: NAVD 88</li></ul>North American Vertical Datum of 1988<br />
    4. 4. Geodetic Datum is a reference system from which measurements are made<br />Examples: NAD 27, NAD 83, WGS 84, ITRF<br />Adjustment is a mathematical process of adjusting observed positions based on standard (control) positions<br />Ex: NAD 83(1986), NAD 83(1991), NAD 83(1997), <br /> NAD 83(2007), NAD 83(2011)<br />
    5. 5. Constancy of Position vs. Accuracy of Position<br />Consistent coordinate systems have existed for essentially 200 years<br />The accuracy has continually improved<br />
    6. 6. Positional Accuracy ImprovementsOver Time <br />
    7. 7. HORIZONTAL SHIFTS From NAD 27…… NAD 83 <br />
    8. 8. Quick Demo: Obtaining Geodetic Control……Using NGS’ DSWorld software with Google Earth<br />
    9. 9. Horizontal changes <br />Example:<br />Station “Kollath” (PID NH1578), Dane County Southwest of Madison<br />
    10. 10. NGS CORS map<br /><br />
    11. 11. Reasons for the new Multi-Year CORS Solution - <br />Public release in July 2011<br />Info at =><br />
    12. 12. NAD 83(2011) epoch 2010.00<br />New adjustment:<br /><ul><li>Target release is end of 2011
    13. 13. Reality is it may be Spring of 2012</li></ul>Will NGS develop a transformation tool?<br /><ul><li>There will likely be a local transformation tool</li></li></ul><li>NOTE: Due to very limited presentation time, this slide and the following five were not part of my live presentation . They were included in this printed handout as a reference for anyone interested in acquiring DSWorld or Google Earth.<br />DSWorld is a free NGS software program, Google Earth may be free<br />The next slides show you how to obtain them<br />
    14. 14. “DSWorld” - Open the NGS main page at<br />Roll Pointer over<br />“TOOLS” button<br />“DOWNLOAD PC SOFTWARE”<br />
    15. 15. Click on:<br />User Contributed Software<br />
    16. 16. click on<br />DSWORLD (Version *.**)<br />
    17. 17. DSWorld Installation Tip<br />Hint: Save the “” download file in a folder that is within two directories of your C: drive prompt….<br />Examples:<br /><br />or <br /><br />
    18. 18. Download “GOOGLE EARTH” at :<br />Click here<br />