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M. Vespe et al.
8.3.4.1 Contextual Data – Risk of Pollution
The contextual data are exploited to identify and properly map areas of influence of
both ports and main ship corridors. Specifically, data sources used for the traffic density estimations are (i) ICOADS data for long term observational records, and (ii)
Automated information System (AIS) for almost NRT and more accurate assessments. Whereas for port influence areas, the World Port Index data are injected,
weighted on the basis of the availability of oil terminals. Once processed and identified the main areas at risk, both data sources are integrated and mapped into a GIS
layer to present the risk information integrated output.
8.3.4.2 Metocean Data – Detection Capability
The information considered here is related to metocean data that directly or indirectly could be exploited to identify phenomena affecting SAR imagery, in particular
the oil spill detection process. Specifically, the data sources used by the authors are
described below:
• Wind Data: can be thought of as the main driving force generating Bragg waves,
therefore directly affecting the detection capabilities. The data are retrieved from
SeaWinds on QuikSCAT monthly averaged products, containing information
about wind speed and direction 10 m above the sea surface. The data are processed and parameterised then in two variables (1) wind speed range for mapping
areas according to their suitability for oil spill detection, and (2) wind fronts
for mapping wind masses interaction associated with potential decrease of wind
velocity and thus yielding false positives.
• Sea Surface Temperature (SST): variations on the SST may affect the stability
of the atmosphere above. This effect may have an impact on the wind stress and
indirectly modify the sea surface modulation. False alarms are likely to happen in
the oil spill detection process under this specific circumstance. Water temperature
strong gradients are therefore mapped over SST layer. The Data for the mapping
of water fronts was retrieved from (1) AVHRR PathFinder V5 product providing temporal monthly averages as a result of the re-analysis of older AVHRR
data, and (2) MODIS/AQUA: derived from the MODIS IR channels using two
channels in either the thermal IR (11–12 μm) or channels in the mid-IR region
(3.8–4.1 μm).
• Chlorophyll-A: such information is injected as an indicator of biogenic activity that, under certain favourable circumstances of quantity of light energy and
inorganic nutrients, may produce the release of biogenic oil films, i.e. lookalikes. The relevant data are retrieved from the JRC Mersea (Mersea website)
monthly averaged regional products. The detection capability degree is derived
using Chlorophyll-A concentration threshold. This threshold is set on the basis of
the extensive analysis of ENVISAT SAR imagery over the Mediterranean Basins
(oligothrophic environment) with synchronous Chlorophyll-A measurements
from MERIS sensor.
M. Vespe et al.
8.3.4.1 Contextual Data – Risk of Pollution
The contextual data are exploited to identify and properly map areas of influence of
both ports and main ship corridors. Specifically, data sources used for the traffic density estimations are (i) ICOADS data for long term observational records, and (ii)
Automated information System (AIS) for almost NRT and more accurate assessments. Whereas for port influence areas, the World Port Index data are injected,
weighted on the basis of the availability of oil terminals. Once processed and identified the main areas at risk, both data sources are integrated and mapped into a GIS
layer to present the risk information integrated output.
8.3.4.2 Metocean Data – Detection Capability
The information considered here is related to metocean data that directly or indirectly could be exploited to identify phenomena affecting SAR imagery, in particular
the oil spill detection process. Specifically, the data sources used by the authors are
described below:
• Wind Data: can be thought of as the main driving force generating Bragg waves,
therefore directly affecting the detection capabilities. The data are retrieved from
SeaWinds on QuikSCAT monthly averaged products, containing information
about wind speed and direction 10 m above the sea surface. The data are processed and parameterised then in two variables (1) wind speed range for mapping
areas according to their suitability for oil spill detection, and (2) wind fronts
for mapping wind masses interaction associated with potential decrease of wind
velocity and thus yielding false positives.
• Sea Surface Temperature (SST): variations on the SST may affect the stability
of the atmosphere above. This effect may have an impact on the wind stress and
indirectly modify the sea surface modulation. False alarms are likely to happen in
the oil spill detection process under this specific circumstance. Water temperature
strong gradients are therefore mapped over SST layer. The Data for the mapping
of water fronts was retrieved from (1) AVHRR PathFinder V5 product providing temporal monthly averages as a result of the re-analysis of older AVHRR
data, and (2) MODIS/AQUA: derived from the MODIS IR channels using two
channels in either the thermal IR (11–12 μm) or channels in the mid-IR region
(3.8–4.1 μm).
• Chlorophyll-A: such information is injected as an indicator of biogenic activity that, under certain favourable circumstances of quantity of light energy and
inorganic nutrients, may produce the release of biogenic oil films, i.e. lookalikes. The relevant data are retrieved from the JRC Mersea (Mersea website)
monthly averaged regional products. The detection capability degree is derived
using Chlorophyll-A concentration threshold. This threshold is set on the basis of
the extensive analysis of ENVISAT SAR imagery over the Mediterranean Basins
(oligothrophic environment) with synchronous Chlorophyll-A measurements
from MERIS sensor.