Chemistry Reference
In-Depth Information
5.3 NUV/IALFS fusion and composite image generation
The NUV signature of an oil spill exhibits more or less intense brightness
gradients that are correlated with the thickness and the complex refractive
index of the spilled oil. A spatially inhomogeneous optical thickness of the
oil spill is associated with a spatially inhomogeneous transmission of the
water-leaving radiance through the oil film. In addition, changes in the sur-
face reflectance of the oil film may also contribute to the observed bright-
ness gradients. It was shown on the basis of field data that NUV images
can be calibrated with IALFS data to give the
lidar optical thickness
ț
o, l
of the oil spill (Robbe and Zielinski 2004, Robbe 2005). The lidar optical
thickness ț
o, l
is directly proportional to the thickness of the oil film. The
IALFS-based measurement of ț
o, l
corresponds to an excitation wavelength
of 308 nm and a detection wavelength of 344 nm (centre wavelength of the
water Raman band). So far, information on lidar optical thickness has only
been available within the field of view (FOV) of the IALFS, i.e. FOV =
28.4°. The proposed calibration procedure extends the measurement and
visualisation of lidar optical thickness to the FOV of the IR/UV-LS, i.e.,
FOV = 87.3°. This is not only beneficial for visualisation, but also for en-
hanced volume estimation. Figure 8 shows a fused NUV/ IALFS image of
lidar optical thickness overlaid with extracted thermal and ultraviolet fea-
tures. This is the thickness map generated by OSSAS; all essential infor-
mation required by the airborne sensor operator is integrated in a single
map.
6 External information processing
The high-level information products derived onboard the surveillance air-
craft are not only useful for the airborne sensor operator. They are also
beneficial for decision and response mechanisms on shore and at sea. The
use of the internally derived high-level information outside the surveill-
ance aircraft is defined as
external information processing
. The relay of
tactical information to ground stations is possible via data downlink. In
this context, it is beneficial that the generated high-level information re-
quires much less memory than the original raw data.
6.1 Internet-based GIS in airborne oil spill remote sensing
Geographical Information Systems (GIS) are instruments for management,
display and statistical analysis of geographic information. They turned out
to be useful for many scientific and commercial applications. The use of
GIS technology for the visualisation of remote sensing data and associated
