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xGeoid16 – what’s new and the results

xGeoid16 – what’s new and the results. S Holmes 1 , X Li 2 and YM Wang 3 1 SGT Inc. USA 2 ERT Inc. USA 3 National Geodetic Survey, NOAA, USA International Symposium on Gravity, Geoid and Height Systems 2016 Thessaloniki | Greece | 19 – 23 September 2016. Outline.

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xGeoid16 – what’s new and the results

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  1. xGeoid16 – what’s new and the results S Holmes1, X Li2 and YM Wang3 1 SGT Inc. USA 2 ERT Inc. USA 3 National Geodetic Survey, NOAA, USA International Symposium on Gravity, Geoid and Height Systems 2016 Thessaloniki | Greece | 19 – 23 September 2016

  2. Outline Introduction to xGEOID model series Data used in xGEOID16 Airborne data editing/adjustment Geoid computation and validation Conclusions and future work

  3. GRAV-D and Next Vertical Datum Next vertical datum for North America will be based on a gravimetric geoid (GEOID2022) by combining the latest satellite models, GRAV-D airborne gravity over the whole U.S.A. and terrestrial gravity data. Currently GRAV-D covers over 50% of the planned areas Experimental geoid (xGEOID) series has been computed annually since 2014 (http://beta.ngs.noaa.gov/GEOID/xGEOID/) This year’s model is xGEOID16

  4. xGEOID16 Two geoid models for comparison purpose: - xGEOID16A: using all available data EXCLUDING GRAV-D - xGEOID16B: using all available data INCLUDING GRAV-D airborne gravity data All models are computed in an area enclosed between latitude 5˚ to 85˚; longitude 170˚ to 350˚ at 1’x1’ grid size. Data used: GOCO05S satellite gravity model EGM2008 NGS terrestrial gravity data 3" digital elevation model GRAV-D airborne gravity data (model B only)

  5. Thinned Raw Residuals wrt EGM2008 (δg, mGal)

  6. GRAV-D Data Editing/Adjustment GRAV-D data were cleaned by a) Removing block biases (relative to EGM2008) b) Removing line biases by using crossover adjustment c) Removing outliers, down-weighting suspect values

  7. Block Median Relative to EGM2008 (Removed)

  8. Line Biases from Crossover Adjustment (Removed)

  9. Residuals wrt EGM2008, RETAINED in Data Grid after Edit

  10. GRAV-D Information EXCLUDED from the Final Residual Grid

  11. GRAV-D Geoid Contribution (Alaska)

  12. GRAV-D Geoid Contribution (Gulf of Mexico)

  13. Validation Against GPS/LevelingStandard Deviation of Discrepancies (cm)(Summary)

  14. Summary xGEOID models provide a preliminary view of GEOID2022 where GRAV-D is flown. The GRAV-D airborne gravity contribution can reach decimeters in areas where the existing terrestrial gravimetry is poor or unavailable. GPS/L comparisons showed that the xGEOID16B should have a relative accuracy of ~1.5 cm along GSVS11 and GSVS14.

  15. Future Work Computation of xGEOID17 Continuation of research on: - data cleaning - data editing - error modeling - topographic effect Preparation of a new geoid model for GSVS17

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