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by David Conner Geodetic Advisor to the State of Ohio National Geodetic Survey, NOAA Dave.Conner@noaa.gov

by David Conner Geodetic Advisor to the State of Ohio National Geodetic Survey, NOAA Dave.Conner@noaa.gov. GRAV-D the International Great Lakes Datum and a Tale of Subsidence Presented at a meeting of the Great Lakes Regional Height Modernization Consortium Columbus OH October 13-14, 2011.

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by David Conner Geodetic Advisor to the State of Ohio National Geodetic Survey, NOAA Dave.Conner@noaa.gov

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  1. by David Conner Geodetic Advisor to the State of Ohio National Geodetic Survey, NOAA Dave.Conner@noaa.gov GRAV-D the International Great Lakes Datumand a Tale of SubsidencePresented at a meeting of the Great Lakes Regional Height Modernization ConsortiumColumbus OHOctober 13-14, 2011

  2. What is GRAV-D? (1) • Gravity for the Redefinition of the American Vertical Datum • An NGS project whose target is to redefine the official civilian vertical datum as the geoid, realized through the use of GNSS technology and a gravimetric geoid model over at least the United States and its territories • GRAV-D could eliminate the need to use leveling to “bring in the datum” Last Updated 12 October 2010 (DAS)

  3. What is GRAV-D? (2) • Official NGS policy as of Nov 14, 2007 • Airborne Gravity Snapshot • Absolute Gravity Tracking • Re-define the Vertical Datum of the USA by 2022 (at current funding levels) • Part of the NGS 10 year plan (2008-2018) • Target: 2 cm accuracy orthometric heights from GNSS and a geoid model Last Updated 12 October 2010 (DAS)

  4. What is GRAV-D? (3) • GRAV-D means fast, accurate, consistent orthometric heights everywhere in the USA • GPS already gives fast accurate ellipsoid heights • If the geoid were modeled (and monitored) to highest accuracy…fast, accurate orthometric heights, anywhere, anytime • No need to use leveling to “bring in the datum” Last Updated 12 October 2010 (DAS)

  5. What is GRAV-D? (4) • GRAV-D will mean: • Primary access to the vertical datum will be through a GNSS receiver and a gravimetric geoid model • One consistent vertical datum for all of North America • CONUS, Alaska, Hawaii, PR, VI • Available for adoption by • Canada, Mexico, Caribbean, Central America Last Updated 12 October 2010 (DAS)

  6. FY12-13 Great Lakes Plan – GRAV-D FY12 = White, FY13 = Orange

  7. Sept-Nov 2011 GRAV-D

  8. IGLD … what is it? The IGLD is a dynamic height system. Dynamic heights, by definition, define a water level surface. Their use is not limited to the Great Lakes but they are the base height system used for IGLD 85 in the Great Lakes. Dynamic heights are the reference of choice for large hydraulic systems everywhere. IGLD heights are corrected dynamic heights. NAVD 88 heights are orthometric heights.

  9. IGLD … “I” is for International! Management of these waters is governed by International Treaty administered by the International Joint Commission with representatives from the US and Canada. US scientific agencies have Canadian counterparts. Published Great Lakes water level data are coordinated by government agencies in both countries to ensure agreement. Coordinated basic hydraulic and hydrologic data are required to solve numerous international problems related to joint use of Great Lakes waters

  10. IGLD … Why is it important? The Great Lakes are a vast hydraulic system with water levels and flows influenced by engineered channels and control structures. The entire region is tilting due to post-glacial rebound (aka glacial isostatic adjustment … GIA) at a rate of about 60 cm (two) feet per century. The absolute rate of change at a given location must be considered along with the relative rate of change across the region. The overall Great Lakes basin is tilting

  11. National Spatial Reference System (NSRS) NOS has two fundamental backbone systems … - GPS CORS (3-D) by NGS - Tide and Water Level Gauges (height) by CO-OPS Cleveland Water Level Gauge and GPS CORS

  12. Who and What is CO-OPS? The Center for Operational Oceanographic Products and Services (CO-OPS) is an element of NOAA. Their responsibilities include: Monitoring tides/water levels and currents. Maintaining a network of some 54 water level gauges throughout the Great Lakes and their connecting channels. Determining heights associated with the International Great Lakes Datum (IGLD), in cooperation with NGS and our International partners in Canada.

  13. Vertical rate of change due to Post-Glacial Rebound International Great Lakes Datum of 1985 (IGLD 85), IGLD 2015 is coming

  14. Lake Erie … ~ 1-2 ft Seasonal fluctuation, ~ 6 ft Long term fluctuation Storms can cause short term fluctuations of up to ~ 8 ft

  15. IGLD … Why is it useful? It is a dynamic height system and can be used to relate various data to a common water level surface The IGLD provides a mechanism for the US and Canada to reference heights to a common datum throughout the Great Lakes region Each country has adopted other vertical datums for general use. The Canadian vertical datum is CGVD 28. The US vertical datum is NAVD 88.

  16. IGLD … When/where is it used? It is used for basic hydraulic and hydrologic data related to engineering and scientific works on or near Great Lakes waters in both the US and Canada These works include things related to navigation and management of water … navigation charts, dredging, marine boundary determination, bridges, locks, dams, sewage and drainages systems, and much more.

  17. IGLD … Why is there more than one? The IGLD is revised about every 30 years to remove the effect of GIA from published heights. IGLD 85 is the current datum. It was preceded by IGLD 55, USLS 35, and various outer datums. Efforts are underway now to compute IGLD 2015

  18. From the Great Lakes Commission http://www.glc.org/ Resolution: Maintaining Accuracy of the International Great Lakes Datum (IGLD) Adopted on February 23, 2010 Whereas, movement of the earth’s crust across the Great Lakes - St. Lawrence River system occurs on a very gradual, continuous and non-uniform basis (in some areas in the magnitude of centimeters per decade), referred to as “glacial isostatic adjustment” or rebounding of the land surface from the weight of glaciers that retreated over 10,000 years ago; and Whereas, water levels in the Great Lakes - St. Lawrence system fluctuate on a short-term, seasonal, and long-term basis, requiring careful and accurate measurements within an accurately established vertical datum; and Whereas, the safety and economic viability of the Great Lakes commercial navigation industry, the extensive recreational boating community and ports/harbors across the region all rely heavily on accurate water level forecasts and maintenance of congressionally authorized dredging programs to provide depths in the navigation channels including waterways connecting the Great Lakes; and

  19. page 2 of 3 Whereas, all coastal zone management, including erosion prediction, flood prediction and response, and coastal structure design, construction and maintenance, rely upon an accurate vertical elevation datum; and Whereas, all coastal habitat restoration, rehabilitation, creation, enhancement, improvement and protection activities currently underway and expected to be implemented under the Great Lakes Restoration Initiative require an accurate vertical datum; and Whereas, prediction of the magnitude, timing and duration of climate variability and global climate change as it affects the Great Lakes – St. Lawrence River system, and the development of adaptive management approaches thereto, require accurate water level measurements and forecasts; and Whereas, the vertical elevation datum for the Great Lakes, known as the International Great Lakes Datum (IGLD), first established in 1955 and last updated in 1985, needs to be updated every 25 to 35 years to reflect continuous and differential changes in land surface elevations across the region.

  20. page 3 of 3 Therefore, Be It Resolved, that the Great Lakes Commission urges the National Oceanic and Atmospheric Administration (NOAA) to prioritize the IGLD update to complete this work by 2015, and to coordinate their activities with Canadian federal and provincial partners, to ensure that this foundational vertical datum is maintained to the highest accuracy possible using the best available technologies; and Be It Finally Resolved, that the Great Lakes Commission urges the U.S. Congress to provide necessary financial resources to complete the IGLD by 2015, and further requests that the Canadian federal government provide a commensurate share to ensure timely completion of this important endeavor. Adopted at the 2010 Seminnual Meeting of the Great Lakes Commission, Washington, D.C., Feb. 22-23, 2010.

  21. Fairport Harbor, a Tale of Subsidence

  22. 3053 GARAGE FRR-1000-0 3053 FENCE NOS GAUGE HOUSE 3053 E 3053 WORKS K321 3053 D 3053 GATE 3053 LIGHTHOUSE X 323 3053 F A.MOSS 9/05/2006 FAIRPORT, OH 9063053

  23. Gauge reference marks Subsidence 5 cm/25 years

  24. Gauge reference marks Subsidence 5 cm/25 years

  25. Fairport Harbor – more nearby mining activityThe OHLA CORS is subsiding at ~4mm/year, four times faster than other CORS in the areaThe first order level line across northern Ohio was established 30 years ago, has not been re-leveled, and there are no definite plans to do so.Where else is subsidence ocurring, and how would we know?

  26. Additional Information The NGS 10 year plan (2008-2018) http://www.ngs.noaa.gov/INFO/NGS10yearplan.pdf The GRAV-D Project http://www.ngs.noaa.gov/GRAV-D Socio-Economic Benefits of CORS and GRAV-D http://www.ngs.noaa.gov/PUBS_LIB/Socio-EconomicBenefitsofCORSandGRAV-D.pdf Last Updated 12 October 2010 (DAS) 29

  27. Further Information • NOAA, NOS, National Geodetic Survey www.ngs.noaa.gov • NOAA, NOS, Center for Operational Oceanographic Products and Services http://www.co-ops.nos.noaa.gov/ For data request information incl IGLD55 and USLS35: User Services: (301) 713-2815

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