IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS003 Poster presentation 1892
Robust Satellites Techniques for oil spill detection and monitoring
Mr. Daniele Casciello
DIFA PHD
Pergola Nicola, Tramutoli Valerio, Lacava Teodosio
In last years, the environmental pollution of the sea due to technological hazards, as the oil spills, outcoming
from different sources (oil rigs releases, illegal vessels discharges, tanker accidents, etc.) still
continue. As stated in different conferences, there is an urgent need for improved management of the
sea and coastal zones in terms of monitoring and mitigation of technological hazards. Satellite remote
sensing could contribute in multiple ways, in particular for what concerns early warning and real-time
(or near real-time) monitoring. Several satellite techniques exist, mainly based on the use of SAR
(Synthetic Aperture Radar) technology, which are able to recognise, with sufficient accuracy, oil spills
discharged into the sea. Unfortunately, such methods cannot be profitably used for real-time detection
in whatever geographic area, because of the low observational frequency assured by present satellite
platforms carrying SAR sensors (which can offer observation frequency from few hours up to few
minutes at medium and low latitudes). On the other hand, the potential of optical sensors aboard
meteorological satellites, has not been yet fully exploited and no reliable techniques have been
developed until now for this purpose. A new satellite technique for oil spill detection and monitoring is
discussed in this paper. It is based on the general approach called RST (Robust Satellite Technique,
Tramutoli, 2005) which was already applied for monitoring other natural hazards related to volcanic
activity, earthquakes (Tramutoli, 2001), floods, forest fires (Tramutoli, 1998). Briefly, RST approach is
an automatic change-detection scheme that considers a satellite image as a space-time process,
described at each place (x, y) and time t, by the value of the satellite derived measurements V (x, y, t).
Generally speaking an Absolute Local Index of Change of the Environment (ALICE) is computed and this
index permits to identify signal anomalies, in the space-time domain, as deviations from a normal state
preliminarily defined, for each image pixel, (e.g. in terms of time average and standard deviation) on
the base only of satellite observations collected during several year in the past, in similar observational
conditions (same time of the day, same month of the year). By this way local (i.e. specific for the place
and the time of observation) instead than fixed thresholds are automatically set by RST which permit to
discriminate signal anomalies from those variations due to natural or observational condition variability.
Using AVHRR observations in the Thermal (TIR), the approach was applied to Kuwait and Saudi Arabia
oil spill event occurred in January 1991 during the Gulf War (Cross, 1992, Casciello et al., 2004), to the
Seky Baynunah event occurred in March 1994 (Tseng, 1995) and now applied for the San George
Argentina Uruguay event occurred in February 1997 (Liu et al., 2000). To reduce problems of TIR
fluctuations due to the meteorological and climatological conditions a Robust Estimator of TIR anomalies
(RETIRA) was implemented and used too. This estimator, was quite effective to reduce this kind of
problems, and also to enhance the anomalous signals on the sea due to the oil polluted areas with a
good detection capability and a good reliability too (up to 0% of false alarms) in different observational
conditions. Thanks to the high repetition rate offered by NOAA polar satellites, the proposed method
offers a first opportunity to plan high-frequency monitoring systems for oil spill at global scale. Although
these results need to be confirmed by further analyses on number of events and in different
observational conditions, this work surely encourages to continue the research in this field. Moreover,
the complete independence of the RST approach on the specific sensor and/or satellite system, will
ensure its full exportability on the new generation of Earth Observation satellite sensors which, thanks
to their improved capabilities, could actually guarantee timely, reliable and accurate information.