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Airborne Gravimetry Projects by Technical University of Denmark
Arne V. Olesen and Rene Forsberg DTU Space, National Space Institute Technical University of Denmark
17/04/2008 Presentation name 2 DTU Space, Technical University of Denmark
Good Global models
GRACE, GOCE, EGM2008, EGM2020? Altimetry contributes over the oceans (O. Andersen, DTU-13)
But need more detailed gravity in many places to get ’few centimeter’ geoid model for GNSS based height systems.
Strong danish research tradition in physical geodesy: Krarup, Tscherning
GRAVSOFT package for geoid computation (Forsberg)
GOCE gravity GOCE geoid +/- 100 m
Why airborne gravity?
17/04/2008 Presentation name 3 DTU Space, Technical University of Denmark
Advantages of airborne gravity: – intermediate and short
wavelengths ..impossible from space
– seam-less coverage between land and ocean (high population dens, flooding mitigation)
– inaccesible areas (jungles, ice sheets, marshes, shallow water …)
– Fast and economical
Airborne Gravity FP4 – Environment and climate, 1996 AGMASCO Airborne Geoid Mapping System for Coastal
Oceanography
How to get this to work? Challenges: accelerations in all directions and
where is the plumb line? and we want accuracy ~0.000001 G or 1 mGal
17/04/2008 Presentation name 4 DTU Space, Technical University of Denmark
Bottom line: • We were successful • Reasonable noise level • Good control of the medium
to longer wavelengths • ie geodetic quality
17/04/2008 Presentation name 5 DTU Space, Technical University of Denmark
Malaysia: 02, 03, 14, 15, 16+ Philippines: 14 Indonesia: 08, 09, 10, 11 1600 hours airborne ~430,000 km
Southeast Asia
17/04/2008 Presentation name 6 DTU Space, Technical University of Denmark
Joint BIG+NGA+DTU project
Contribution to global models (EGM201?) and an effort to establish a satellite based height system for Indonesian Archipelago
The survey in numbers:
•2008 - 2011
•730 hours airborne
•205,000 km
•1.6 mill. sq.km
Indonesian airborne gravity and geoid mapping survey Multi-year, not finished yet
Very dynamic region (ring of fire), strong variations in gravity field
2009+10
2008 2010+11
17/04/2008 Presentation name 7 DTU Space, Technical University of Denmark
jawa
sulawesi papua
Indonesia national vertical datum network 40 years of tedious leveling work under the tropical sun
Indonesia Mean Dynamic Topography, DTU-13 (O. B. Andersen)
17/04/2008 Presentation name 8 DTU Space, Technical University of Denmark
-Fill-in by EGM08 (mainly marine)
-2D PSD estimation with FFT
-Isotropic averaging of PSD
-Conversion to degree variance
GOCE R5 Airborne
How much did the airborne data mean Can we put a number on?
17/04/2008 Presentation name 9 DTU Space, Technical University of Denmark
East Africa
Contribution to EGM2008 and EGM2020
Cooperation with National surveys in Ethiopia, Tanzania, Mozambique and Malawi
Effort to establish nationwide satellite based height systems
17/04/2008 Presentation name 10 DTU Space, Technical University of Denmark
17/04/2008 Presentation name 11 DTU Space, Technical University of Denmark
Mozambique/Malawi area Mean Std. dev. Minimum Maximum
Airborne -11.8 33.9 -180 146
GOCE R5-DIRECT residuals -1.9 24.5 -141 141
EGM08 residuals -1.5 15.3 -123 91
GOCE R5 residuals EGM08 residuals
17/04/2008 Presentation name 12 DTU Space, Technical University of Denmark
East Africa
Very turbulent flight conditions The L&R meter cannot handle
this turbulence level but the iMAR still works fine
Other sensors would not cope with this: Chekan, GT-1A
17/04/2008 Presentation name 13 DTU Space, Technical University of Denmark
LOMGRAV: Lomonosov ridge airborne gravity and magnetic survey
Collect geophysical data to support Danish claim for continental shelf beyond 200 nautical miles
17/04/2008 Presentation name 14 DTU Space, Technical University of Denmark
New bathimetry map from IBCAO + gravity Døssing et al, 2010
17/04/2008 Presentation name 15 DTU Space, Technical University of Denmark
ICEGRAV Antarctica 2010+2011+2013 airborne geophysical survey IAA – UTexas – NPI – BAS – DTU •Gravity •Magnetics •Ice penetrating radar
17/04/2008 Presentation name 16 DTU Space, Technical University of Denmark
What is under the ice?
17/04/2008 Presentation name 17 DTU Space, Technical University of Denmark
The PolarGap campaign (ESA) A logistic challenge Iljushin IL 76 (fuel, air drop) Basler BT67 (camp input) Twin-Otter (survey plane)
17/04/2008 Presentation name 18 DTU Space, Technical University of Denmark
•A few pictures from antarctica
PolarGap FD83 camp
The camp
The team
The fuel
17/04/2008 Presentation name 19 DTU Space, Technical University of Denmark
The last piece
17/04/2008 Presentation name 20 DTU Space, Technical University of Denmark
2-axis
Chekan L&R (TAGS) 3-axis
GT-2A AirGrav (Sanders) Strapdown
iMAR RQH Gradiometer
Falcon (Lockheed Martin)
1 mGal @ 5-7 km
Geodesy, science and exploration
0.5 mGal @ 2-4 km
Widely used for exploration
better than 1 mGal @ 4 km
The new kid
0.2 mGal @ 0.3 km
(but weak in medium to long waveband)
Common airborne gravimeters
17/04/2008 Presentation name 21 DTU Space, Technical University of Denmark
Gradiometry over Northern Zeeland (shale gas exploration)
CPH CPH
17/04/2008 Presentation name 22 DTU Space, Technical University of Denmark
Gradiometry over Northern Zeeland (shale gas exploration)
17/04/2008 Presentation name 23 DTU Space, Technical University of Denmark
The near future •New inertial sensor (iMAR RQH) •PhD, developing algorithms for IMU •Still international demand for geodetic quality airborne gravity data (coastal zone, Africa)
•Consultancy, capacity building •MEMS for drones
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