1. 45 th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Hilton Anchorage Hotel Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Part II: GRAV-D Airborne Survey Update Daniel R. Roman and Vicki A. Childers

2. Survey Priority Order Alabama test region Puerto Rico/US Virgin Islands Gulf of Mexico (except Florida) Alaska Eastern US Seaboard (& FL)/Great Lakes Western US Seaboard Hawaii, Guam/CNMI, American Samoa Interior CONUS Aleutian Islands

3. GRAV-D Airborne Surveys Gulf of Mexico 2008-09 (AL08, LA08, LA09, TX09) Puerto Rico/US Virgin Islands 2009 (PV09) Alaska 2008-11 (AK08, AK09, AK10-01, AK10- 02, AK10-03) California 2011 (CA11-01) - 11 surveys, ~10% of total area flown 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 3

4. Gulf of Mexico Surveys 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 4

5. Gulf of Mexico Preliminary Gravity 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 5

6. Puerto Rico/US Virgin Islands 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 6

7. Preliminary Gravity Puerto Rico 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 7

8. California 2011 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 8

9. California 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 9

10. Alaska Surveys 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 10 2008 2009 2010 2010&11 2011 Plan Fairbanks Anchorage

11. 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 11 AK Preliminary Gravity

12. Basic Airborne Operations Instrumentation: – Relative gravity meter aboard aircraft – Inertial measurement unit – GNSS receivers included in both instruments – GPS base stations (three for redundancy) Gravity tie – New absolute measurement – Relative tie to meter height in plane 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 12

13. GRAV-D Team Vicki Childers Theresa Diehl Sandy Preaux Justin Dahlberg Greg Watson Tim Wilkins Carly Weil (not pictured) Also pictured NOAA pilots Scott Price and Mark Sweeney 2010 NGS Convocation13

14. Field Capability Developing the project from scratch Instrumentation – Acquisition, engineering, installation, troubleshoot Operating procedures Data Handling – QC: equipment working, data quality sufficient – Metadata creation, data archival, shipment to HQ 14

15. Field Capacity: Challenges Field team depth Need a dedicated aircraft – Present NOAA capacity is limited – Need both a long- and a shorter-range aircraft – Mods for USGS magnetometer Needed instrumentation – Inertial measurement unit – Electronics racks

16. Data Processing: Software Development GPS processing – GrafNav – Kinematic GPS Challenge Gravity data processing – Aerograv Problem – Newton software – Programmer has created user-friendly version for 2.0 Newton 2.0

17. Airborne Data Flow

18. GRAV-D Web Page Program events are recorded here Survey progress will be displayed Plan to make data and software available here 18 http://www.ngs.noaa.gov /grav-d

19. Project Challenges Optimum survey heights: 5Kft, 20kft, 35kft? – Alabama AL08 tested flights at all three altitudes – Downward continued noise amplified 7 times in 35kft data, 2 times in 20kft data – Comparisons of gravity field recovery with EGM08 continued to h=0 shows poor results at 35kft 20,000 ft was identified as best height – Still above most weather – Aliasing issues can be dealt with

20. Newton 1.0 Residuals Δg: +NGS ‘A-EGMs’ (N=1080) vs. Terr. (h=0m) 35,000 ft 20,000 ft 5,000 ft

21. Improvements to GPS Processing? GPS Challenge produced 15 solutions from 9 groups We will look to use the software that yields the best results GrafNav will continue to be field QC software 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 21

22. Improvements to Gravity Processing Thorough analysis of all aspects of gravity data processing Rigorous treatment of all corrections Final challenges remain: – Off-level correction – Low-pass filtering 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 22

23. Early Version Data Residuals with AGM08 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 23

24. AK08 Residual Gravity Profiles 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 24 As compared with Min = -50.76 Max = 31.46 Mean = 1.52 SD = 4.42 Original

25. Early Version Crossover Errors 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 25

26. Crossover Plots for AK08 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 26 As compared with Min = -12.90 Max = 12.03 Mean = -0.19 SD = 4.29 mGal Original

27. AK08 Residual Gravity Profiles 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 27 Lines 121-124 (Airborne – EGM08)

28. AK08 vs EGM08 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 28 EGM08AK08

29. Break time! Next up: Geoid Modeling 45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 29