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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
aircraft line by line in the ultraviolet (À = 320 nm to 380 nm)
and in the thermal infrared (A = 8.5 um to 12.5 um). The MWR
is a passive, short-range sensor operating on three channels
(18.7 GHz, 36.7 GHz, 89 GHz) and is used to measure the oil
layer thickness. The LFS is an active, short range sensor used to
specify the oil type and the layer thickness. To collect evidence
concerning possible polluters a photographic and video camera
are used. Detailed descriptions of the sensors are given by
Trieschmann et al. 2001 and Trieschmann et al. 2003. Details of
the sensors are depicted in table 1. The most important features
of the sensors are highlighted in grey.
Table 1. Characteristic properties of the sensors
SLAR UV IR MWR LES
Range @ 300m wide narrow
; m. : narrow, +250m 2o
flight altitude +30km x t75m
Classification
br: no yes
capabilities :
Sensitivity on oil 50um
T A > 0.1 um to
film thickness N.A. 20.1u >10um to :
AR 20 um
m 2.5mm
Spatial resolution 60m by 10m pixel-
30m 3.5m 3.5m >5m to-pixel
(perp.) distance
Detection of oil no es
spills below surface y
Operating at night yes | no yes yes yes
Film thickness yes,
determination nO 50jum | yes, 0.1 jtm
to to 20 um
2.5mm
Measuring ; ; Conical,
; 8 Line-by-line
geometry , 5Hz
clouds,
Impaired by no clouds | clouds no flight
altitude
The German Exclusive Economic Zone (EEZ) is depicted in
Figure 1. The EEZ in the North Sea is monitored on 11
different flight routes. Assuming a SLAR swath width of 60 km
between 33% and 65% of the EEZ is covered during the
surveillance flights. The EEZ in the Baltic Sea is monitored on
2 flight routes. Over 93% of the EEZ is covered on both flight
routes. On average 2 surveillance flights a conducted each day.
i |
i G'E
ou Ww Sweden ^
Wi, (
A)
: . Baltic Sea |^
tu AI ee proms 1564
North Sea ^ Bb Cl oe |
Lote BY E S prts
AN Y - * ut m v A za"
\ e 5d 7
amt rj T T. i
jan wt T MS) x \
: E er x - e. ( Germany \
m \ f {
: + Netherland |
p IP ! | German Exclusive Economic Zone (EEZ)
9 50 100 150 Kiometers |
J EEZ Copyrght BIG 2004
Figure 1. The German EEZ
3. COMBINED SATELLITE/AIRCRAFT CAMPAIGN
In 2003 a 5 month oil spill monitoring campaign using satellite
data in near real time and aerial surveillance was conducted.
This campaign was part of the EU funded project
OCEANIDES.
RADARSAT-1 ScanSAR Narrow images and ENVISAT ASAR
Wide Swath images (Table 2) were acquired, processed and
visually analysed for oil slicks by Kongsberg Satellite Services
AS (KSAT, Tromse, Norway).
Table 2. Specifications for RADARSAT-1 and ENVISAT
ASAR imagery (ESA, 2002 and RSI, 1999)
RADARSAT-1I
ScanSAR Narrow
ENVISAT ASAR
Wide Swath
Spatial resolution [m] 50 150
Nominal area covered 300 x 300 400 x 400
[km]
Polarisation HH VV
For satellite evaluation the combined aircraft/satellite campaign
was conducted by using the following procedure:
l. The aircraft will take off at the time of the satellite
overpass to be at the centre of the EEZ at the time the
satellite analysis will be avaiable.
2. Max. 60 minutes after the overpass KSAT will inform
the German Pollution Control Authority by phone and
report: position, area and the confidence of the slick
(Low, Medium or High)
3. The crew onboard the aircraft will immediately be
informed by radio about the message from KSAT to
direct the aircraft to the location of the potential oil
slick.
If no oil spill is detected KSAT informs via e-mail.
The operators use the following guidelines to determine the
confidence level of a slick (Solberg, et al., 2004):
High confidence:
e The slick has a large contrast to gray-level surroundings.
e The surroundings are homogenous, with a constant gray-
level.
e. The wind speed is moderate to high, i.e. approximately 6 -
10 m/s.
e Ship or platform directly connected to slick
Medium confidence:
e The wind speed is moderate to low, i.e. approximately 3 -
6 m/s.
* The slick has a diffuse/low contrast to the grey-level
surroundings in moderate to high wind speed.
* The shape of the slick is irregular, i.e. the edges are not
smooth.
Low confidence:
* Low wind areas are located nearby.
e Natural slicks (e.g. biological, algae or fractal streaks at
very low wind) are located nearby.
e The slick has diffuse edges and/or an irregular shape.
The operator analysing the images use information about wind
speed, wind direction, oil rig location, coastlines and national
territory borders as auxiliary information.
After receiving the information about possible oil slicks the
aircraft tried to confirm this information. Figure 2 shows an
example of an oil slick from an oil rig detected on a
RADARSAT-1 image and confirmed by the aircraft. The
corresponding information reported from KSAT and the aircraft
crew are depicted in Table 3.
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