A presentation about SAR Remote Sensing in the field of ARGOMARINE Project

1. SAR Remote Sensing in
Argomarine
M. Babiker, T. Hamre,
Nansen Environmental and Remote Sensing Center (NERSC)
Norway
New Strategies and Technologies for safety of Navigations in the
Mediterranean Sea
21 November 2012, Petroferraio, Italy

2. Outline
n Background
n SAR remote sensing for oil spill
n SAR for Argomarine
n Summary

3. Background
Oil spills seriously affect the marine ecosystem and cause political and scientific concern
since they have serious effects on fragile marine and coastal ecosystem. The amount of
pollutant discharges and associated effects on the marine environment are important
parameters in evaluating sea water quality. Satellite images can improve the possibilities
for the detection and monitoring of oil spills as they cover large areas and offer an
economical and easier way of continuous coastal areas patrolling.
http://www.myhero.com/go/hero.asp?hero=Oil_Team_cfes_US_2012

4. 15 November 2012 Last updated at 20:11 GMT
BP gets record US criminal fine over Deepwater disaster
BP has received the biggest criminal fine in US history as part of a $4.5bn
(£2.8bn) settlement related to the fatal 2010 Deepwater Horizon disaster.

5. ESTIMATES OF GLOBAL INPUTS OF OIL TO THE
MARINE ENVIRONMENT
• Natural seeps: 46%
• Discharges from consumption of oils (operational discharges from
ships and discharges from land-based sources): 37%
• Accidental spills from ships; 12%
• Extraction of oil: 3%
http://oils.gpa.unep.org/facts/sources.htm

6. The most commonly used remotely sensed system to detect ocean
pollution is Synthetic Aperture Radar (SAR) imagery.
The Prestige oil spill, Spain, caused by the sinking of an oil tanker in 2002

7. SAR = Synthetic Aperture Radar
An active instrument that transmit/receive EM radiation, store data in
amplitude and phase (real and imaginary part)
• Works in the presence of clouds, day and night
• Operates at microwave (or radar) frequencies
• Fine resolution is independent of the platform height, so images with the
same geometric resolution (order of 10 m) can be obtained from satellites
as from airplanes

8. z
Antenna
Azimuth
Range
Swath
x
y
Illuminated area!
A short pulse is emitted by the antenna and then the amplitude and
phase of the backscattered signal is recorded as a function of time This is
repeated over again while the platform is moving Thus a 2-dimensional
image is generated.

9. Advantages compared to optical remote sensing
All weather capability (small sensitivity of clouds, light rain)
Day and night operation (independence of sun illumination)
No effects of atmospheric constituents (multitemporal analysis)
Sensitivity to dielectric properties (water content , biomass, ice)
Sensitivity to surface roughness ( ocean wind speed, currents ,oil spill )
Accurate measurements of distance (interferometry)
Sensitivity to man made objects
Sensitivity to target structure (use of polarimetry)
Subsurface penetration

10. SAR-based oil spill monitoring in Argomarine:
SAR image ordering and acquisition for the test areas
The following Satellite were investigated:
ENVISAT ASAR (launched March 2002)
ALOS PALSAR (November 2006)
TerraSAR-X (June 2007)
COSMO-SkyMed (June 2007)
Radarsat-2 (December 2007)

11. NERSC set up automatic download of images for the two test areas, using
software tools developed by NERSC in other RTD projects
During the project period
208 ENVISAT ASAR images
were downloaded for the
Tuscan Archipelago
And 280 images for The
National Marine Park of
Zakynthos.
3 TerraSAR-X were ordered and
purchased
3 Radarsat2 images ordered
and purchased

12. SAR analysis for oil spill detection and classification
A selection of archived images from the ENVISAT ASAR (Advanced Synthetic
Aperture Radar) covering both study areas were analyzed.
The Next ESA SAR Toolbox (NEST) was used to analyse the ASAR data.
An ENVISAT ASAR Wide swath image acquired on the 7 June 2008 covering the Tuscany Archipelago (B) oil spills map
generated from image (a) Red is potential oil spill, light blue currents and waves black low wind speed. A confirmed oil spill
is demarcated with green circle.

13. An ENVISAT ASAR image mode image acquired on the 14 March 2008 covering Zakynthos (B) oil
spills map generated from image (a) Red is potential oil spill, light blue currents and waves black low
wind speed.

14. Classification of oil spills and surface phenomena in dual
polarisation images
All the available methods
and models for
discrimination between oil
spills and look-likes using
polarimetric SAR are still
experimental and no
concrete method or model
are available for that.
Alternating polarizations ENVISAT
ASAR image (VV/VH) acquired on
the 01 August 2003 (A) VV
polarization (B) VH polarization
(C) RBG image from VV, VH and
VV/VH (D) Wind speed and
direction generated from the
image.

15. Alternating polarizations
ENVISAT ASAR image (VV/
VH) acquired on the 11
May 2007 (A) VV
polarization (B) VH
polarization (C) RBG
image from VV, VH and
VV/VH (D) Wind speed and
direction generated from
t h e i m a g e .
Most of the surface
phenomena, oil spills and
look-alikes investigated can
be detected clearly in both
polarizations VV and the
HH, on the other hand the
same features can’t be
detected using cross
polarizations (VH, HV).

16. SAR estimates of wind and currents
The CMOD4 and Doppler shift algorithms have been applied on a selected
ENVISAT ASAR images from the two areas to estimate wind speed and current.
An ENVISAT ASAR wide Swath (VV) of the 27 of August 2010 covering the Tuscan Archipelago.

17. ENVISAT ASAR wide Swath (VV) of the 15 of October 2010 covering Zakynthos Island.

18. Distribution and density of oil spills in the test
areas
Seventy two archived ENVISAT ASAR (Advanced Synthetic Aperture Radar) Wide
Swath images were analyzed for oil spill distribution and density.
The oil spill detection algorithm was applied for all the images and only dark
features with high potential to be oil spill were analyzed. A density map was
created for each study area.

19. Summary
SAR is the most applicable spaceborne sensor for operational oil spill
detection, mostly
because of its all-weather/all-day detection capabilities and wide coverage
The largest challenge in detection of oil spills in SAR images is accurate
discrimination between oil spills and look-alikes.
For operational purposes, there is a need for coordination between satellite
overpasses and aerial surveillance flights.
Future SAR missions are crucial for sustainable operational oil spill detection
services.

20. Tha
nks