John Ellingson 2

Bio: John Ellingson currently serves as the National Geodetic Survey (NGS) State Geodetic Advisor to Wisconsin. In his role as the State Geodetic Advisor, John works with surveyors, engineers and GIS professionals, as well as local, state and Federal agencies, helping them better understand and use the geodetic control of NGS’s National Spatial Reference System. John is licensed as a Professional Land Surveyor and a Professional Engineer in Wisconsin. On October 1, 2016, John will be transitioning to the position of NGS Great Lakes Regional Advisor, where he will support the states of Michigan, Indiana, Illinois, and Wisconsin.

Progress Toward the International Great Lakes Datum Update

The earth’s crust in the Great Lakes Region continues to rebound from the disappearance of glaciers that covered the area thousands of years ago. This crustal movement, or isostatic rebound, causes gradual changes to the elevations of the bench marks surrounding the Great Lakes. Bench mark elevations are used to calibrate the water level gages, whose elevations are defined by a common datum developed by Canada and the United States. That common datum is known as the International Great Lakes Datum or IGLD. The US and Canada are now working to update IGLD to account for crustal changes that have occurred over the past 30 years. This presentation will provide more information on the process of updating IGLD and why it is important to do so.

datum, NGS, IGLD, Great Lakes