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Effect of High Resolution Altimetric Gravity Anomalies on the North America Geoid Computations

Effect of High Resolution Altimetric Gravity Anomalies on the North America Geoid Computations. Yan M. Wang and D. Roman National Geodetic Survey NOAA Montreal, Canada, May 17-21, 2004. Recent geoid computations at NGS.

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Effect of High Resolution Altimetric Gravity Anomalies on the North America Geoid Computations

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  1. Effect of High Resolution Altimetric Gravity Anomalies on the North America Geoid Computations Yan M. Wang and D. Roman National Geodetic Survey NOAA Montreal, Canada, May 17-21, 2004

  2. Recent geoid computations at NGS • Milbert, D. G., 1991b: GEOID90: A high-resolution geoid for the United States. Eos, 72(49), pp. 545-554. • Smith, D.A. and D.G. Milbert, 1999: The GEOID96 high resolution geoid height model for the United States, Journal of Geodesy, V. 73, N. 5, pp. 219-236. • Roman, D.R. and D.A. Smith, 2000, Recent investigations toward achieving a one centimeter geoid, presented at GGG2000 session 9 of the IAG Symposium in Banff, Alberta, Canada from July 31 - August 4, 2000. • Roman, et al., Assessment of the New National Geoid Height Model, GEOID03 , ACSM Meeting, 4/19, 2004.

  3. Gravimetric geoid computation Stokes integral /1DFFT • Topographic reduction: terrain correction at 1/3/30 arc seconds • EGM96 remove/restore: gravity anomaly of the reference model is removed, reference geoid is added back to residual geoid • Indirect effect

  4. Data Used for USGG2003 • NGS gravity database: 1,264,372 • NIMA gravity data: 2,064,898 • Altimetric gravity anomaly: 688,876 • GTOPO30 and NGSDEM99 • EGM96 global gravity model up to degree and order 360 • Ellipsoidal correction from Sideris et al. (2003)

  5. Altimetry Gravity Models

  6. RMS Values of Gravity Differences(mgal)

  7. Geoid Differences(Mean/RMS values in cm)

  8. GPS/leveling Differences (cm)

  9. GPS/leveling Differencesin Florida (cm)

  10. GPS/leveling DifferencesBy Region (Mean/ RMS values incm)

  11. Conclusions • Altimetry gravity models differ at ±3 mgal RMS values (excluding few outliers in KMS99) • Geoid differences can reach 10 cm in coastal regions (land area), few cm in areas thousand miles away from the ocean • Geoid changes caused by GSFC00.1 improve the US gravimetric geoid

  12. Conclusions (cont.) • Sea surface topography implied by GSFC00.1 MSS and USGG03 closely emulate the POCM4b • Ocean/land interface problems (diff. reference systems, lack gravity data)

  13. Web Information • http://www.ngs.noaa.gov/GEOID/PRESENTATIONS/

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