Transcript GRAV-D International Great Lakes Datum and a Tale of Subsidence the

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
by
David Conner
Geodetic Advisor to the State of Ohio
National Geodetic Survey, NOAA
[email protected]
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)
2
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 (20082018)
• Target: 2 cm accuracy orthometric
heights from GNSS and a geoid
model
Last Updated 12 October 2010 (DAS)
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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)
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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)
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FY12-13 Great Lakes Plan – GRAV-D
FY12 = White, FY13 = Orange
Sept-Nov 2011 GRAV-D
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.
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
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
National Spatial Reference System (NSRS)
Cleveland Water Level Gauge and GPS CORS
NOS has two fundamental
backbone systems …
- GPS CORS (3-D) by NGS
- Tide and Water Level Gauges
(height) by CO-OPS
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.
Vertical rate of change due to Post-Glacial Rebound
International Great Lakes Datum of 1985 (IGLD 85), IGLD 2015 is coming
Lake Erie … ~ 1-2 ft Seasonal fluctuation, ~ 6 ft Long term fluctuation
Storms can cause short term fluctuations of up to ~ 8 ft
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.
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.
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
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
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.
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.
Fairport Harbor, a Tale of Subsidence
3053 GARAGE
FRR-1000-0
3053 FENCE
NOS GAUGE HOUSE
3053 E
K321
3053 WORKS
3053 D
3053 GATE
3053 LIGHTHOUSE
X 323
3053 F
A.MOSS
FAIRPORT, OH
9063053
9/05/2006
Gauge reference marks
Subsidence 5 cm/25 years
Gauge reference marks
Subsidence 5 cm/25 years
Fairport Harbor – more
nearby mining activity
The OHLA CORS is subsiding
at ~4mm/year, four times
faster than other CORS in the
area
The 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?
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)
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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