recent development in gravity and bathymetry … · recent development in gravity and bathymetry...

Recent development in gravity and bathymetry mapping from satellite

altimetry - The DTU10 fields

Ole B. Andersen

ESA/ESRIN, Symposium on Oil & Gas, September, 2010

2 DTU Space, Technical University of Denmark

• Global Altimetric gravity from Satellite (sea surface height) • Double retracking / repicking• The Arctic Ocean – Completing global Coverage• Accuracy, Coherency• Bathymetry + Bouguer Anomaly estimation. • DTU Space: Proprietory gravity fields

• Examples–Arctic / Polar regions / East Greenland –Florida Keys

Outline



Main Offshore Sedimentary Basins

• From KMS02 -> DTU10 Focused on improving gravity field in – Shallow water regions – Polar regions



Mapping the sea surfacefrom spaceUsing radar.



DTU10 Features - Truly global gravity field (90°S-90°N)- 1-2 km resolution grid (1 minute = 1/60 °)- Based on retracked / repicked Satellite altimetry

h = N + MDT + n(t)

Gravity from Sea surface heights

rN

rNg γγ 2−

∂∂−=Δ

High Res gravity on the ocean surface



Double Waveform retracking/repicking

First Retrack: Gain more data and better spatial coverageSecond Retrack: Enhanced SSH estimation (repicking/retracking)

First Retracking:EAPRS rule-based Expert System (P. Berry, Leicester University UK):Identify 12 different waveform type (ocean, ice, patch, specular……..) Retrack using specially designed retrackers.

Globally: 9% gain but focused on Polar and Near Shore regions.

Waveform



Polar Regions: Heavy Gain in Coverage

ORIGINAL ESA ERS-1 DATA Retracked ERS-1 1Hz

14489 Data KMS02 DNSC08/DTU10

Standard 18.1 4.1 / 4.0

Max 119.9 42.0



Old ”Global” marine gravity field (i.e. Sandwell/Smith lim: 72N)

Polar Gap: ERS2/ENVISAT + ICESAT + ArcGP

ArcGP complete Polewards coverage above 86 °N

ERS-1/2 Radar up to 82 °N (KMS02)

ICESAT laser between 80 °N and 86°N



DTU 10 Free Air Gravity Anomalies

Land fill in: EGM2008 gravity anomalies



Coastal regions heavily improved

A´ll > 10.000 obs Std(KMS02)

Std(SS 16.1)

6.54 7.11

4.27

4.05

4.98

5.05

5.40

4.16

4.06

5.74

5.36

5.60

Std(DNSC08)

KMS02-DNSC08 %Improvement

Purple (0-20 m DEPTH) 3.46

3.14

3.83

4.89

4.38

4.89

48

Dark Blue (20-50 m) 26

Light Blue (50-200 m) 6

Green (200-500 m) 15

Yellow (500-1000 m) 22

Red + Pink (1000-5000 m) 13



Strong currents

Steep Bathymetry

Large differences KMS02, DNSC08,SS16.1

Lots of marine Gravity

Gulf of MexicoFlorida Keys

10100 marine Obs Std Dev (mGal)

KMS02 4.99

SS 16.1 / SS18.1 5.89 / 3.12

DTU10 2.78

Difference KMS02-DNSC08 Difference SS16.1 – DNSC08



Δg ”Error estimate

mGal



Coherence Spectrum (Caribbean)

202550100 13Wavelength (km)

800 km Marine

gravity profile

RMS signal 32 mGal,

RMS Diff: 2.86 mGal

Cohe

renc

e

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1DNSC08KMS02

17.5 km



DNSC08 Bathymetry

Consistent 1-min grid to DNSC08 Gravity

For easy estimation of Bouguer gravity anomalies.

Improved GEBCO – 1min bathymetry using DTU10 Gravity

Example DNSC08-Bouguer

by D. Fairhead – GTECH



Whats Next

• Cryosat II

• Delay Dobbler

Advantages: Higher accuracyHigher Track resolution (300 m)Stabil accuracy (no sig wavehgt)

And Then: Sentinel – 3



DTU Space assist in:

Potential field research &Proprietary Field Generation

Optimal merging of dataGlobal grids + Survey dataRegional subset (Q-control)

Example of merging DNSC08 gravity

Field with airborne data off eastcoast

Of Greenland for exploration

Off+Onshore Northeast Greenland

Bathymetry prediction

Global grids + Survey data

Bouguer Anomaly prediction

Merging Gravity + Bathymetry

DNSC08 Bathymetry



SummaryDNSC08 / DTU10

Resolution: 1 minute by 1 minute (2 km by 2 km)True global gravity field (90°S to 90°N)

Internet point of download: FTP: ftp.spacecenter.dk/pub/DTU10WWW: www.space.dtu.dk

Proprietory grids / quality control / data services etc: Contact Ole B. Andersen [email protected]

Additional Consistent Products

Mean Sea Surface / MDTAltimetric derived BathymetryError/Accuracy field.

Aknowledgement:P. Knudsen (DTU Space).P. Berry, J. Freeman (De Montfort)S. Kenyon, N. Pavlis(NGA)

ftp://ftp.spacecenter.dk/pub/DTU10



Thank you

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