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Beyond GEOID12: Implementing a New Vertical Datum for North America Daniel R. Roman, Ph.D. Neil D Weston, Ph.D.

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Presentation on theme: "Beyond GEOID12: Implementing a New Vertical Datum for North America Daniel R. Roman, Ph.D. Neil D Weston, Ph.D."— Presentation transcript:

1 Beyond GEOID12: Implementing a New Vertical Datum for North America Daniel R. Roman, Ph.D. Neil D Weston, Ph.D.

2 Outline Why isn’t NAVD 88 good enough anymore? Selection of a datum surface (W 0 ) – Tide gauges – SST/MODT Aerogravity coverage Summary TSC04B: Heights, Geoid, & Gravity Paper 5691, 08 May 2012, 0900 F.I.G. Working Week May 2012 Rome, Italy 2

3 Why isn’t NAVD 88 good enough anymore? Approximate level of error known to exist in the NAVD 88 zero elevation surface TSC04B: Heights, Geoid, & Gravity Paper 5691, 08 May 2012, 0900 F.I.G. Working Week May 2012 Rome, Italy 3

4 TSC04B: Heights, Geoid, & Gravity Paper 5691, 08 May 2012, 0900 F.I.G. Working Week May 2012 Rome, Italy 4 Available Tide Gauges

5 SST, TBM’s and the Geoid P,T,S ≠ constant/uniform Geoid + SST = LMSL (as seen at tide gauge) TSC04B: Heights, Geoid, & Gravity Paper 5691, 08 May 2012, 0900 F.I.G. Working Week May 2012 Rome, Italy 5 Geoid = “Global” MSL surface Local MSL SST/MODT

6 SST (MODT) Models Foreman et al Thompson-Demiorov 2006 TSC04B: Heights, Geoid, & Gravity Paper 5691, 08 May 2012, 0900 F.I.G. Working Week May 2012 Rome, Italy 6

7 Tide Gauge comparisons limited to where SST models exist TSC04B: Heights, Geoid, & Gravity Paper 5691, 08 May 2012, 0900 F.I.G. Working Week May 2012 Rome, Italy 7 62,636, m 2 /s 2

8 Current GRAV-D Coverage TSC04B: Heights, Geoid, & Gravity Paper 5691, 08 May 2012, 0900 F.I.G. Working Week May 2012 Rome, Italy 8 GRAV-D: Gravity for the Redefinition of the American Vertical Datum

9 Summary NAVD 88 is insufficient to meet cm-level needs Must use highly accurate gravimetric geoid New W 0 best fits most Tide Gauges – SST models remove significant variability in LMSL – Same W 0 value adopted by IAU and IERS – Neglects Arctic but also Mexico & Caribbean TSC04B: Heights, Geoid, & Gravity Paper 5691, 08 May 2012, 0900 F.I.G. Working Week May 2012 Rome, Italy 9

10 Summary U.S.A & Canada have agreed to use this W 0 – Will serve as Canadian Vertical Datum in 2013 – It is the likely value for U.S. in 2022 GRAV-D aerogravity will bridge gap – Satellite gravity models will provide unification – Surface gravity & DEM’s give high frequency – Aim is for cm-level accuracy in geoid and GNSS TSC04B: Heights, Geoid, & Gravity Paper 5691, 08 May 2012, 0900 F.I.G. Working Week May 2012 Rome, Italy 10


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