2. A Comparison of Continuation Models for Optimal Transformation of Gravimetric Data By: Joanelle Baptiste Elizabeth City State University, NC Supervisor: Dr. Daniel Roman 8/6/04

3. Line Office (Overview) NOAA Ocean Service (NOS) National Geodetic Survey (NGS) Geosciences Research Division (GRD)

4. Terms to be familiar with Ellipsoid Geoid Gravimetric Gravity anomaly: Δg = g obs -γ Mean Sea Level

5. Models of the Earth

6. Figure of the Earth

7. OCEAN Earth’s Surface “Ellipsoid” Geopotential Surface “Geoid” P Q h N Geoid height N = h – H Gravity anomaly Δg = g P 0 – γ Q P 0 plumb line Ellipsoid height, h = distance along ellipsoid normal (Q to P) Orthometric height, H = distance along plumb line (P 0 to P) Geoid height, N = distance along ellipsoid normal (Q to P 0 ) P, Q and P 0 all have the same lat, lon values. H ∟ ∟

9. Planar Approach Earth’s curved surface flat plane of the model space

10. Findings: predicted less actual Height 1km Min. -0.8 Max. 0.9 Ave. 0.0 St. Dev. 0.1 2km-1.71.6-0.20.2 3km-2.82.2-0.50.2 4km-3.92.5-0.90.3 5km-5.22.4-1.50.4 6km-6.32.3-2.30.4 7km-7.71.8-3.20.5 8km-9.11.1-4.20.5 9km-10.60.4-5.40.6 10km-12.2-0.8-6.70.6

11. Residual Values 1 km 8 km

12. Conclusion The planar method can be used to upward (or downward) continue data with some controls Because of systematic effects (ringing), a region for continuation larger than actually desired should be used (add about 0.5 degrees to latitude/longitude limits) Systematic average must also be accounted for and may be data dependent (i.e., a bias is introduced)

13. Importance of this Research Supervisor/field assignment Operational applications -Engineering -Navigational aid -Storm surge -Coastal flooding

14. Accomplishments via EPP Contributions : Participant NOAA

15. Acknowledgements NOAA EPP staff Dr. Daniel Roman Mr. Edward Allen Mr. Eric Linzey Ms. Sonita Tiwari Ms. Lucy Hall Ms. Laura Cutrer Class of 2004 (all my love)

16. Questions?

17. The End