Geoid Modeling, GRAVD and Height Mod

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Geoid Modeling, GRAV-D and Height Mod
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Why make a new vertical datum?
Courtesy of Dr. Dennis Milbert
20 FEB 2009 Salt Lake City, UT
ACSM-MARLS-UCLS-WFPS Conference 2009
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Vertical Shift due the National Readjustment of
2007
20 FEB 2009 Salt Lake City, UT
ACSM-MARLS-UCLS-WFPS Conference 2009
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Hybrid Geoid Height Models (e.g., GEOID09),
Gravimetric Geoid Height Models (e.g., USGG2009)
and Conversion Surfaces using GPS on BM data

Earths Surface
Ellipsoid
Hybrid Geoid
Gravimetric Geoid

• Gravimetric Geoid systematic misfit to BMs but
  best fits true heights
• Hybrid Geoid converted to fit local BMs, so
  best fits NAVD 88 heights
• Conversion Surface model of systematic misfit
  derived from BMs in IDB

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(Beta) GPSBM 2009 for CONUS
20 FEB 2009 Salt Lake City, UT
ACSM-MARLS-UCLS-WFPS Conference 2009
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USGG2009 (Beta)
GEOID09 (Beta)
20 FEB 2009 Salt Lake City, UT
ACSM-MARLS-UCLS-WFPS Conference 2009
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Extent of Gravity Coverage Shown are the
differences between NGSIDB value and EGM08 model
20 FEB 2009 Salt Lake City, UT
ACSM-MARLS-UCLS-WFPS Conference 2009
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GRAV-D Gravity for the Redefinition of the
American Vertical Datum

• Official NGS policy as of Nov 14, 2007
• 38.5M over 10 years
• Airborne Gravity Snapshot
• Static Geoid
• Absolute/Satellite Gravity Tracking
• Time Dependent Geoid
• Re-define the Vertical Datum (using gravimetric
  geoid as reference surface) of the USA by 2017

http//www.ngs.noaa.gov/GRAV-D/
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A North American Geoid
20 FEB 2009 Salt Lake City, UT
ACSM-MARLS-UCLS-WFPS Conference 2009
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For a more thorough discussion,see the
USGG2009/GEOID09 session later today