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