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
Dec 23, 2015
45th 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
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
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 flown45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska
Thursday, 0800-12003
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, 0800-12004
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, 0800-12005
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, 0800-12006
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, 0800-12007
California 2011
45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska
Thursday, 0800-12008
California
45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska
Thursday, 0800-12009
Alaska Surveys
45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska
Thursday, 0800-120010
2008
2009 20102010&11
2011 Plan
2011 Plan
Fairbanks
Anchorage
45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska
Thursday, 0800-120011
AK Preliminary Gravity
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, 0800-120012
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 Convocation 13
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
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
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
Airborne Data Flow
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
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
Newton 1.0 ResidualsΔg: +NGS ‘A-EGMs’ (N=1080) vs. Terr. (h=0m)
35,000 ft 20,000 ft 5,000 ft
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, 0800-120021
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, 0800-120022
Early Version Data Residualswith AGM08
45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska
Thursday, 0800-120023
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, 0800-120024
As compare
d with
Min = -50.76Max = 31.46Mean = 1.52 SD = 4.42
Ori
gin
al
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, 0800-120025
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, 0800-120026
As compare
d with
Min = -12.90Max = 12.03Mean = -0.19SD = 4.29 mGalO
rigin
al
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, 0800-120027
Lines 121-124
(Airborne – EGM08)
AK08 vs EGM08
45th Annual Alaska Surveying & Mapping Conference February 21-25, 2011
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska
Thursday, 0800-120028
EGM08AK08
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, 0800-120029