Geodetic Control in Wisconsin
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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 Geodetic Control in Wisconsin Presentation Transcript

  • Geodetic Control
    in Wisconsin
    Wisconsin Land Information Association
    La Crosse, Wisconsin
    May 17, 2011
    John Ellingson
    Wisconsin State Geodetic Advisor , cell 202-306-6904
  • 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.
  • Geodetic Datums
    NGS is mandated to define the datums for the United States
    Definition of a Datum: A set of constants specifying the coordinate system used for geodetic control
    Part of the National Spatial Reference System (NSRS)
    For all federal civil mapping
    Challenge to update due to technological improvements
    • Current horizontal datum: NAD 83
    North American Datum of 1983
    • Current vertical datum: NAVD 88
    North American Vertical Datum of 1988
  • 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)
  • Constancy of Position vs. Accuracy of Position
    Consistent coordinate systems have existed for essentially 200 years
    The accuracy has continually improved
  • Positional Accuracy ImprovementsOver Time
  • Quick Demo: Obtaining Geodetic Control……Using NGS’ DSWorld software with Google Earth
  • Horizontal changes
    Station “Kollath” (PID NH1578), Dane County Southwest of Madison
  • NGS CORS map
  • Reasons for the new Multi-Year CORS Solution -
    Public release in July 2011
    Info at =>
  • NAD 83(2011) epoch 2010.00
    New adjustment:
    • Target release is end of 2011
    • Reality is it may be Spring of 2012
    Will NGS develop a transformation tool?
    • There will likely be a local transformation tool
  • 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.
    DSWorld is a free NGS software program, Google Earth may be free
    The next slides show you how to obtain them
  • “DSWorld” - Open the NGS main page at
    Roll Pointer over
    “TOOLS” button
  • Click on:
    User Contributed Software
  • click on
    DSWORLD (Version *.**)
  • DSWorld Installation Tip
    Hint: Save the “” download file in a folder that is within two directories of your C: drive prompt….
  • Download “GOOGLE EARTH” at :
    Click here