45 th annual alaska surveying & mapping conference february 21-25, 2011 hilton anchorage hotel...

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



Gulf of Mexico Preliminary Gravity




Puerto Rico/US Virgin Islands




Preliminary Gravity Puerto Rico




California 2011




California




Alaska Surveys



Thursday, 0800-120010

2008

2009 20102010&11

2011 Plan

2011 Plan

Fairbanks

Anchorage



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



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



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



Thursday, 0800-120022

Early Version Data Residualswith AGM08



Thursday, 0800-120023

AK08 Residual Gravity Profiles



Thursday, 0800-120024

As compare

d with

Min = -50.76Max = 31.46Mean = 1.52 SD = 4.42

Ori

gin

al

Early Version Crossover Errors



Thursday, 0800-120025

Crossover Plots for AK08



Thursday, 0800-120026

As compare

d with

Min = -12.90Max = 12.03Mean = -0.19SD = 4.29 mGalO

rigin

al

AK08 Residual Gravity Profiles



Thursday, 0800-120027

Lines 121-124

(Airborne – EGM08)

AK08 vs EGM08



Thursday, 0800-120028

EGM08AK08

Break time!

Next up: Geoid Modeling



Thursday, 0800-120029

45 th annual alaska surveying & mapping conference february 21-25, 2011 hilton anchorage hotel...

Documents

alaska surveys

pv09 alaska

geoid modeling

ak preliminary gravity

childers slide

gulf of mexico surveys

relative gravity meter

ngs convocation13 slide