1. Integration of Gravity Data Into a Seamless Transnational Height Model for North America Daniel Roman, Marc Véronneau, David Avalos, Xiaopeng Li, Simon Holmes, and Jianliang Huang Session 5: Paper S5-075

2. Gravity for the Redefinition of the American Vertical Datum (GRAV-D) Overview Not just aerogravity – Use to clean/salvage two million terrestrial data – Makes improved geoid – Must use satellite data – Yields a vertical datum Neighboring countries – Must develop a North America Model Session 5 Paper S5-075 1730 10 OCT 2012 Gravity Geoid and Height Systems Venice, Italy 09-12 OCT 2012 2

3. GRAV-D Status Session 5 Paper S5-075 1730 10 OCT 2012 Gravity Geoid and Height Systems Venice, Italy 09-12 OCT 2012 3 TX09

4. Discussion of GRAV-D intent Goal of a cm-level accurate geoid Must meld different gravity sources To do this: must resolve systematic errors in gravity observations – Compare aerogravity to satellite data – Constrain aerogravity to GRACE/GOCE – Combined satellite & airborne gravity field model- somewhere between deg 100-250 – Use aerogravity to fix errors and bridge spectral gap with terrestrial surveys – Derive shortest wavelengths from high resolution terrain and density models – Develop a seamless gravity field to 10,800 Rigorously transform to generate geoid heights and DoV’s 4 satellite models (GRACE/GOCE) terrestrial gravity airborne gravity Variance (m 2 ) Satellite-Airborne Transition Band Airborne-Terrestrial Transition Band Session 5 Paper S5-075 1730 10 OCT 2012 Gravity Geoid and Height Systems Venice, Italy 09-12 OCT 2012 ATTB: 150-450 (100-540 with tapers)

5. EGM2008 540 (GOCO03S) – EGM2008 540 (GRACE)

6. ATTB: Degrees 150-450 (100-540)

7. Historical surface data agreements with EGM08

8. More clear Systematic features in Historical surface data, focus on long wavelength

9. More clear short wavelength Systematic features in Historical surface data are detected after adding airborne information

10. Line 3613 Line 5357 Line 2144 Line 5162

11. EGM2008 (GRACE Only) EGM2008 (GOCO03S) GOCO03S+Aerogravity

13. Summary GOCO03S benefits EGM2008 Systematic errors in terrestrial data still exist Such errors lead to systematic geoid errors Must resolve these for cm-level accuracy Aerogravity in Texas differs from terrestrial at the 3-5 mGal range Can be discerned in some terrestrial profiles Data cleaning will be required to resolve these Session 5 Paper S5-075 1730 10 OCT 2012 Gravity Geoid and Height Systems Venice, Italy 09-12 OCT 2012 13

14. Alaska examples

15. QUESTIONS? Session 5 Paper S5-075 1730 10 OCT 2012 Gravity Geoid and Height Systems Venice, Italy 09-12 OCT 2012 15