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The Impact of Littoral Aerogravity on Coastal Geoid Heights

The Impact of Littoral Aerogravity on Coastal Geoid Heights. Daniel R. Roman, Ph.D. XXIV General Assembly of the I.U.G.G. Session GS002: Gravity Field, Paper 9009 Thursday, 5 July 2007, 1110-1124. Talk Outline. Collection Scheme Installation & Equipment GLS05 & GLS06 aerogravity

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The Impact of Littoral Aerogravity on Coastal Geoid Heights

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  1. The Impact of Littoral Aerogravity on Coastal Geoid Heights Daniel R. Roman, Ph.D. XXIV General Assembly of the I.U.G.G. Session GS002: Gravity Field, Paper 9009 Thursday, 5 July 2007, 1110-1124

  2. Talk Outline • Collection Scheme • Installation & Equipment • GLS05 & GLS06 aerogravity • GLS05 lidar comparisons in Tampa Bay, Florida • GLS06 tide station comparisons in northern Gulf Coast (MS, AL, FL) • Summary

  3. VDatum Transformation Tool • Bathy/topo lidar studies • Develop tide surfaces based on mapped features and currents • 7 regions done thus far • Tampa Bay region is already done (GLS05) • Northern Gulf Coast (GLS06) in progress http://nauticalcharts.noaa.gov/csdl/vdatum.htm

  4. N Tide gauge height ellipsoid Instantaneous Ocean Surface LMSL mDOT geoid Geoid (N) = LMSL – Mean Dynamic Ocean Topography (mDOT) Geoid (N) = Inst. SSH – mDOT – Tides – Sea State – inst. DOT

  5. GSL06 & GLS05 Aerogravity

  6. Crossover Differences in GLS06 & GLS05

  7. Residual Gravity in GLS06 & GLS05

  8. Lidar Data: a work in progress • So far, none of the 2006 data have been processed • Limited portions of the 2005 data have been reduced • Data are available in the Bay of Florida region and Tampa Bay region. • Since Tampa Bay is an established VDatum region, we’ll look at it more closely.

  9. Gravity vs. Lidar Collections in GLS05

  10. Gravity vs. Lidar Collections in GLS05

  11. Port Tampa 5.961 UT 0.227 m -0.32 m -0.40 m 5.967 UT 0.239 m 0.031 m 6.759 UT -0.23 m 6.754 UT 0.016 m St. Petersburg 6.745 UT 0.047 m 0.062 m 6.738 UT 6.714 UT 0.175 m 6.706 UT 0.202 m 6.696 UT 0.193 m 0.176 m 6.687 UT 6.983 UT 0.182 m 0.179 m 6.677 UT 6.990 UT 0.191 m 7.001 UT 0.240 m 6.667 UT 0.156 m 7.011 UT 0.237 m Port Manatee 7.020 UT 0.248 m Averaged Residual Lidar Profiles in Tampa Bay (lidar – DOT - geoid) on 29 MAY 2005 0.03 – (-0.40) 0.43 m 0.06 – (-0.32) 0.38 m 0.18 – (-0. 23) 0.41 m

  12. Gravity Data: Mainly Complete • As the GLS05 gravity data are very limited, they could not be used to analyze the gravity field near Tampa Bay other than to provide rough agreement • GLS06 data are much more complete • In conjunction with a DOT model and Tidal Bench Marks (TBM’s), the gravimetric geoid (USGG2003) can be analyzed • This is a simpler comparison than the lidar surface as much of the time-varying aspects are averaged away

  13. Implied Geoid Changes for GLS06

  14. Geoid Heights Compared with Tide Gauges • Top image shows USGG2003 comparison • Triangles note the locations of Tide Gauges within the study area • Note that the dm-level trend along shore • Bottom image shows aerogravity enhanced model comparison • Note there is very little along shore trend • Inclusion of aerogravity seems to have improved the geoid height model with respect to MSL

  15. Proposed Aerogravity Flights for October 2008 and Beyond

  16. Summary • GLS05 gravity is insufficient to clean database • GLS05 lidar still being developed & need better ties • More tide station comparisons in/out of VDatum area • GLS06 gravity very useful in cleaning database • Must still resolve difference in NW GLS06 study area • Will likely need a ground survey comprised of several absolute and many relative observations • GLS06 lidar must be completed

  17. Outlook • A combination of lidar and aerogravity will help to refine future gravimetric geoid models by combining them with ocean and tide models and observations • Such models will become indispensable for such tools as VDatum that seek to accurately and consistently transform between various datums • Work under this study is still in progress, though new data will be collected • Future collection and a larger effort for the entire Gulf Coast region is being planned and budgeted

  18. For Further Information and Related Work • Jarir Saleh, CERP Poster Session, Paper 8789, July 4 On Some Aspects of GLS06 Data Quality assessment and downward continuation • Yan Wang, CERP Poster Session, Paper 12026, July 5 Accurate Account of the Topographic Effect on the Geoid Computations

  19. NGS Staff Daniel R. Roman dan.roman@noaa.gov Yan M. Wang yan.wang@noaa.gov Jarir Saleh jarir.saleh@noaa.gov NRL Staff John M. Brozena john.brozena@nrl.navy.mil Vicki A. Childers vicki.childers@nrl.navy.mil Questions? • NASA Staff • Scott B. Luthcke Scott.B.Luthcke@nasa.gov • David L. Rabine David.L.Rabine.1@gsfc.nasa.gov • Hannes Greim greimh@gmail.com • University of Maryland • Michelle A. Hofton also with NASA michelle@avalon.gsfc.nasa.gov • Sandra A. Martinka formerly NRL sam@atmos.umd.edu

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