77
1 INTRODUCTION
The integration of radar technology with Vessel Traffic
Services (VTS) significantly enhances the detection and
management of oil spills. Radar systems offer direct
detection capabilities by identifying changes in radar
backscatter caused by oil on the water surface. Oil spill
on the sea surface dampens the sea clutter observed by
the radar. This is a result of dampening of the wind
generated capillary wave [1]. The suppression of
capillary waves by oil slicks creates characteristic "dark
spots" on radar images, serving as potential spill
indicators. Additionally, within the VTS framework,
radar indirectly aids in oil spill detection by monitoring
vessel movements and identifying any unusual
behaviour that might suggest a spill incident.
VTS centres play a crucial role in disseminating
information about potential oil spills. When radar
systems detect anomalies indicative of a spill, VTS
networks relay this information to relevant authorities.
Similarly, reports from vessels about oil spills are
rapidly disseminated through the VTS system.
Furthermore, VTS facilitates traffic management
during oil spill response operations. This includes
rerouting vessels to avoid the spill area, establishing
exclusion zones to protect the environment and
facilitate cleanup efforts, and streamlining
coordination with other responders.
The integration of radar data with VTS systems
provides a more comprehensive situational awareness
during oil spill response. For example, if radar detects
an oil slick, VTS data can help identify potential source
vessels in the vicinity. This integration also contributes
to faster response times by enabling rapid generation
and dissemination of alerts.
Prompt detection and monitoring of oil spills in the
marine environment are critical for effective
environmental protection and response strategies.
Leveraging Radar and VTS for Enhanced Oil Spill
Detection
M. Fiorini
1
& R. Trevisani
2
1
Leonardo s.p.a, Roma, Italy
2
GEM elettronica, San Benedetto del Tronto (AP), Italy
ABSTRACT: The Norwegian Clean Seas Association for Operating Companies (NOFO) conducted oil-on-water
exercises in 2018 to evaluate new oil spill response technologies, including advanced radar systems. This study
assesses radar performance based on data collected during these exercises, focusing on the potential of radar
technology to enhance Vessel Traffic Services (VTS) systems. By analysing radar data from various simulated oil
spill scenarios, key strengths, weaknesses, and areas for improvement were identified. Findings highlight the
benefits of integrating radar technology into VTS for improved oil spill detection, tracking, and response. This
includes recommendations for expanding VTS system features to leverage radar data more effectively, such as
developing algorithms for automated oil spill detection and implementing real-time data fusion techniques. The
study demonstrates the potential of radar- enhanced VTS systems to significantly improve oil spill response
capabilities, particularly in challenging conditions.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 19
Number 1
March 2025
DOI: 10.12716/1001.19.01.10
78
Spilled oil rapidly spreads across the water surface,
forming a toxic film that disrupts oxygen exchange and
severely harms aquatic ecosystems. Early detection is
vital for enacting containment measures and
mitigating the long-term impacts on marine life,
ecosystems, and local communities.
This paper presents a comparative analysis of X-
band and Ka-band radar systems, focusing on their
efficacy in detecting oil spills on the sea surface.
However, it is important to acknowledge that radar-
based oil spill detection has limitations, as it can be
influenced by factors such as weather conditions, sea
state, and the features of the oil film.
2 SATELLITE VERSUS LAND/SHIP-BASED
RADAR
Satellite-based radar, particularly Synthetic Aperture
Radar (SAR) such as the European Space Agency
(ESA), COSMO-SkyMed Series, [2], has been
extensively employed for the detection of oil spills
from space. SAR technology is valued for its ability to
provide high spatial resolution imagery that is
independent of range, while operating effectively
under all weather conditions and during both day and
night. This capability enables the remote and near real-
time monitoring of marine oil spills, which is critical for
prompt emergency response and environmental
protection, especially in regions where direct on-site
assessment is impractical.
The detection of oil spills by SAR is achieved
through the identification of dark patches on the sea
surface, which result from the damping effect of oil on
capillary waves. These dark areas contrast with the
surrounding sea clutter, allowing for the delineation of
oil-contaminated zones. However, the presence of
natural look-alikes, such as areas of low wind or
biogenic films, may lead to false positive detections,
[3]. Consequently, advanced image processing and
classification techniques have been developed to
improve the accuracy of spill identification.
Despite its advantages, SAR detection is subject to
certain limitations. The effectiveness of detection is
influenced by sea state and wind conditions, with
optimal performance observed at wind speeds ranging
from approximately 1.5 m/s to 6 m/s (i.e. Beaufort Sea
State up to 3). At wind speeds below this range, the
contrast between oil and the sea surface diminishes,
while higher wind speeds cause increased scattering of
radar signals, thereby reducing detection capability,
[3]. Additionally, the temporal resolution of satellite-
based radar is constrained by satellite revisit intervals,
although recent developments in satellite
constellations have sought to address this limitation.
Recent advances have been made through the
integration of machine learning and deep learning
algorithms with SAR imagery, resulting in enhanced
detection accuracy and speed. Automated and robust
identification of oil spills from satellite data has thus
been increasingly realized, [4].
In contrast, land-based and shipborne radars,
commonly operating within the X-band frequency,
have been utilized for oil spill detection at closer
ranges, typically up to 24 NM at the very latest. These
radar systems can be adjusted to mitigate sea clutter
effects and have demonstrated success in detecting
surface slicks, particularly in coastal and port
environments.
The deployment of shipborne radar offers flexibility
for targeted monitoring and can serve as a
complementary tool to satellite data by providing
higher temporal resolution and immediate local
surveillance. Furthermore, such systems are generally
less costly and can be rapidly deployed in response to
spill events.
However, the detection range of land and ship-
based radars is inherently limited by their lower
altitude relative to satellites. Similar to satellite radar,
environmental conditions such as sea state and wind
speed impose constraints on detection capability.
Moreover, the spatial coverage of these systems is
substantially narrower, and their operation may
require manual control or integration with additional
sensors to ensure effective monitoring.
A comparative analysis reveals that satellite-based
radar systems provide extensive coverage ranging
from regional to global scales, with high spatial
resolution that remains consistent regardless of range.
Temporal resolution, however, is limited by satellite
revisit times.
Conversely, land and ship-based radars offer
continuous local monitoring with higher temporal
resolution but are restricted in spatial coverage. Both
systems exhibit robustness to weather conditions,
though detection efficacy is optimal under moderate
wind speeds.
From a cost and deployment perspective, satellite
infrastructure entails higher expenses, whereas land
and ship-based radar systems are comparatively
economical and more flexible in deployment.
Table 1. Comparative summary
Aspect
Land/Ship-Based Radar
Coverage
Area
Limited to coastal or
local areas
Spatial
Resolution
Moderate, depends on
antenna and altitude
Temporal
Resolution
High, continuous local
monitoring possible
Weather
Independence
Affected by weather
but generally robust
Sea State
Sensitivity
Similar constraints as
satellite radar
Cost and
Deployment
Lower cost, flexible
deployment on
ships/land
Detection
Accuracy
Good, but limited by
range and
environmental
conditions
Use Case
Local monitoring, spill
tracking,
complementary to
satellite data
To summarise, satellite-based SAR remains the
preeminent technology for large-scale, all-weather oil
spill detection due to its broad coverage and high
spatial resolution, making it indispensable for initial
spill identification and ongoing monitoring.
Nevertheless, its temporal resolution is limited by
orbital parameters. Land and ship-based radar systems
provide valuable complementary capabilities, offering
enhanced temporal resolution and localized flexibility,
albeit with range and environmental limitations.
79
3 NOFO OPV EXERCISE
This study is based on data collected during the
Norwegian Oil on Water (NOFO OPV) exercise
conducted on the Frigg field in Norway in 2018 (Figure
1). The NOFO OPV, a biennial exercise conducted in
collaboration between the Norwegian Coastal
Administration and the Norwegian Clean Seas
Association for Operating Companies (NOFO), is
unique in its use of actual oil releases. This allows for
realistic testing of the latest technologies for remote
sensing, containment, and recovery of oil spills,
attracting international participation and attention.
More than 10 cooperating units (Table 2), including
both aerial and naval assets, were involved in the
exercise activities.
Figure 1. NOFO OPV 2018 Exercise Area (Image from
EMODnet: European Marine Observation and Data
Network)
Table 2. OPV 2018 principal operating units [5]
Name
Type
Role
KV Sortland
Patrol Vessel
Oil discharge, Remote
Sensing Exercise
Command and Safety
Strillborg
Offshore Supply Vessel
Experiment with In- Situ
Burning Oil
Torsborg
Offshore Supply Vessel
Experiment with Oil,
Recovery System, (MOS
Sweeper 50)
OV Utvær
Pollution Control Vessel
Exercise Safety
Siem Symphony
Offshore Supply Vessel
Experiment with Oil
Containment Boom
(Spillraider 1200s)
Bøen
Trawler
Oil Spill Protection
Vestbris
Trawler
Oil Spill Protection
Midnight 01 (LN- KYV)
Aircraft
Remote Sensing
Finnguard 01
Aircraft
Remote Sensing
Swecoast 503
Aircraft
Remote Sensing
The 2018 exercise was carried out on the Frigg field,
a decommissioned gas field in the North Sea that
provides a suitable environment for controlled oil spill
experiments, in an area within 10 NM of the position
59° 59’ 00” N, 002° 27’ 00” E.
On the first day (June 6th, 2018), a total volume of
72 m
3
oil emulsion was discharged into the area. The
emulsion was released directly in front of the recovery
system at a distance of approximately 300 m. Part of the
oil spill was recovered, and the other part was
dispersed into the environment, creating a long streak
of oil on the sea surface. The spill was followed by
recovery operations utilizing oil skimmer systems and
oil containment booms. Recovery and oil dispersion
activities continued into the second day (June 7th,
2018). Marine weather conditions remained stable
throughout the two-day trial, with mean wind speeds
ranging from 16 to 21 knots and wind directions
predominantly from north to north-northeast (N-
NNE). The experience at NOFO OPV 2018 highlighted
both the advantages and disadvantages of these
systems and the effect of radar characteristics and
parameters on the outcomes.
Figure 2. OFO OPV 2018 Oil Discharge Scenario From KV
SORTLAND
3.1 Spilled Oil Properties
The 2018 NOFO OPV exercise utilized a specially
formulated oil emulsion derived from evaporated
Oseberg Blend crude oil. This specific crude oil was
chosen due to NOFO's extensive experience in creating
emulsions with it. While the composition of Oseberg
Blend can fluctuate slightly based on production rates,
it is generally classified as a light, paraffinic crude oil
with a density of approximately 840 g/l.
To simulate the weathering process of oil on water,
the Oseberg Blend was evaporated at temperatures
exceeding 200°C. This evaporation process aimed to
replicate the characteristics of oil that has been exposed
to the marine environment for roughly one day,
creating a more realistic scenario for the exercise.
To create a stable oil emulsion for the NOFO OPV
exercise, a specific mixing ratio was used:
− Up to 40% evaporated Oseberg Blend: This forms
the base of the emulsion.
− Up to 10% tungsten (IF 380): Tungsten was added
to increase the emulsion's density, making it easier
to observe and track in the water.
− Minimum 50% seawater: Seawater is the primary
emulsifying agent, helping to disperse the oil and
create a stable mixture.
This formulation builds upon previous exercises.
The 2018 OPV emulsion was largely reused from the
2016 exercise. However, due to the hydrogen sulphide
(H2S) that can accumulate in stored seawater
emulsions, up to 10 litres of H2S remover were added
to ensure the safety and quality of the emulsion [5].
Table 3. Oseberg Blend Properties [6]
Whole Crude Properties
Density @ 15°C (g/cc)
0,827
API Gravity
39,6
Total Sulphur (% wt)
0,20
Pour Point (°C)
-15
Viscosity @ 20°C (cSt)
4,14
Viscosity @ 40°C (cSt)
2,70
80
4 DUAL BAND RADAR SYSTEM
The GEMINI-DB radar system, produced by GEM
Elettronica (an Italian company controlled by
Leonardo s.p.a.), was installed on one of the
cooperating vessels and deployed during the NOFO
OPV trial on both June 6th and June 7th. This dual-
band radar, operating in both X-band and Ka-band, is
designed to provide enhanced situational awareness in
the surveillance of infrastructures and is particularly
well-suited for detecting oil spills in challenging
maritime environments. The combination of X-band
and Ka-band allows the GEMINI-DB to overcome the
limitations of each individual band, providing both
high sensitivity to small oil spills at short ranges (Ka-
band) and robust performance in challenging weather
conditions and at longer ranges (X-band).
Table 4. GEMINI-DB System Characteristics
System Characteristics
Ka-band Radar
X-band Radar
Radar Technology
Pulsed Magnetron
Radar
Pulsed Doppler
Radar
Transmitter Type
Magnetron / Non-
Coherent
Solid State /
Coherent
Transmitter Peak
Power
10 kW
400W
Frequency
[33.600:34.100]
GHz
[9.300:9.500] GHz
Antenna Gain
40 dB
31 dB
Antenna Polarization
Circular
Horizontal
Antenna Horizontal
Beamwidth at -3dB
< 0.3°
< 0.9°
Figure 3. GEM GEMINI-DB X-Ka Dual Band Radar System
The X-band radar employs pulsed Doppler
technology with solid-state transmitters, whereas the
Ka- band radar uses pulsed radar technology based on
magnetron. The lower frequency of the X-band results
in reduced clutter return, enabling more efficient
filtering of external disturbances caused by waves and
rain.
The Ka-band radar, due to its millimeter-
wavelength operation, is significantly more sensitive to
the scattering of very small objects, such as raindrops
and wind-induced facets on the sea surface providing
higher sensitivity for detecting the subtle changes in
backscatter caused by oil. The Ka-band's use of circular
polarization partially mitigates its limitations in rain
and enhances its detection capabilities for depolarizing
objects.
On the other hand, the X-band excels at medium to
high ranges, higher sea states, and poor meteorological
conditions due to its lower frequency. This broader
operational capability of the X-band aligns with its
adoption as the standard for navigation radar under
IMO regulations.
A very first version of the GEMINI-DB radar system
with a non-coherent transceiver was deployed during
NATO Harbour Protection Trials 2008 hosted in
Eckernförde, Germany, demonstrating its versatility in
diverse surveillance applications.
The concept behind this radar system is to combine
the strengths of both bands: Ka-band for improved
small target detection at short range and X-band for
longer detection ranges and better clutter rejection,
making it a valuable tool for oil spill detection and
response [7].
4.1 Radar Installation and Data Acquisition
The GEMINI-DB dual-band radar was temporarily
installed on the Norwegian Coast Guard patrol vessel
KV Sortland at a height of 19 meters above the
waterline.
The radar's radiating sector was positioned on the
port side of the ship, covering an area of approximately
210 degrees.
This configuration allowed for comprehensive
surveillance of the oil spill area during the NOFO OPV
exercise.
Figure 4. GEM GEMINI-DB radiation sector on KV
SORTLAND offshore patrol vessel
During the trials, the following data were recorded:
− X-band raw signal (digitalized): This provides the
raw data from the X-band radar, capturing the
backscattered signals from the sea surface and any
potential oil spills.
− Ka-band raw signal (digitalized): Similar to the X-
band data, this records the raw signal from the Ka-
band radar, offering higher sensitivity for detecting
smaller oil spills.
− GPS data (Latitude/Longitude/Course Over
Ground/Speed Over Ground @ 1 Hz frequency):
This provides precise information about the vessel's
position and movement, which is crucial for
accurately geo-referencing the radar data and
tracking the oil spill's location.
− Gyrocompass data (Heading/Roll/Pitch @ 10 Hz
frequency): This data captures the vessel's
orientation and motion in detail, allowing for
compensation of any movements that might affect
the radar measurements.
81
Figure 5. GEM GEMINI-DB Radar System
installation on KV SORTLAND offshore patrol vessel
A total period of 19 hours with oil-on-water was
recorded, providing a substantial dataset for analysing
the performance of the GEMINI-DB radar in detecting
and tracking oil spills under various conditions.
Additionally, GEM elettronica Oil Spill Detector
(OSD) elaborator was installed on board KV
SORTLAND to process radar and navigation data for
the automatic extraction of oil spill tracks. The GEM
OSD software supported oil spill dispersion operations
during the whole trial. An image of the graphical user
interface is shown in Figure 6.
Figure 6. Screenshot of the graphical user interface of GEM
Oil Spill Detector (OSD) software
Such information should be shared from ship to
shore, enabling the VTS or, more generally, the shore-
side center of the eNavigation, to fulfill one of its core
mission: the protection of the maritime environment,
[8].
Vessel Traffic Services (VTS) and Coastal
Surveillance Systems (CSS), [9], [10], are crucial for
mitigating maritime oil spills, acting as essential
components of marine safety and environmental
protection.
Upon the detection of a potential spill, whether
through advanced radar systems equipped with oil
detection capabilities, visual observation, or reports
from vessels in the vicinity, the eNavigation shore-side
center acts as the first responder. Their immediate
action involves alerting the appropriate emergency
response teams, including specialized pollution
cleanup crews with expertise in containment and
recovery, relevant environmental agencies responsible
for assessing ecological damage and coordinating long-
term remediation efforts, and port authorities who
manage harbor operations and ensure the safety of port
facilities. This rapid notification process is critical in
minimizing the time it takes to initiate an effective
response, thereby reducing the spread and impact of
the spill.
The eNavigation shore-side operators then
coordinate the complex and multifaceted response
efforts that follow, which may include directing vessels
involved in the cleanup operation to the precise
location of the spill using real-time tracking and
communication systems. They also provide crucial
navigational assistance to these vessels, guiding them
through potentially hazardous conditions and
ensuring the safe and efficient deployment of
containment booms, skimmers, and other specialized
equipment to contain the spill's spread. This optimized
vessel positioning is essential for maximizing the
effectiveness of the cleanup operation.
Simultaneously, the eNavigation shore-side
continuously monitors the movement of the oil spill,
utilizing predictive models and real-time data to
forecast affected areas and inform the development of
dynamic response strategies. This continuous
monitoring allows response teams to adapt their tactics
as the situation evolves, ensuring that efforts remain
focused and effective, and minimizing the overall
environmental damage.
The eNavigation shore-side center also serves as a
central hub for information exchange, providing
updates to all stakeholders, including government
agencies, industry representatives, and the public,
ensuring transparency and facilitating a coordinated
response.
Furthermore, the eNavigation shore-side plays a
vital role in ensuring the safety of navigation in the
affected area, which is critical for preventing further
incidents and protecting both the environment and
human life.
Depending on the location and extent of the spill,
the eNavigation shore-side will manage vessel traffic
by providing early warnings to approaching ships,
alerting them to the presence of the spill and potential
hazards. They also establish temporary exclusion
zones with clearly defined boundaries to prevent
further contamination of the affected area and protect
response personnel and equipment operating on-
scene. Deviating shipping routes to guide vessels
safely around the spill is another key function,
ensuring that maritime traffic can continue to move
efficiently while avoiding both direct contact with the
oil and the potential for secondary incidents. This
traffic management is not only critical for preventing
secondary incidents, such as collisions or groundings
that could exacerbate the situation and lead to further
release of pollutants, but also for ensuring the efficient
and safe movement of vessels in the vicinity, including
those directly involved in the cleanup operation. The
eNavigation shore-side center's comprehensive traffic
overview and communication systems are
indispensable for coordinating complex navigational
maneuvers. The eNavigation shore- side leverages
advanced technology and dynamic coordination to
minimize both immediate and long-term
environmental and economic damage from oil spills.
Ultimately, the eNavigation shore- side ensures the
safety, efficiency, and resilience of maritime operations
in the face of such disasters.
82
5 RESULTS
The first processed oil spill radar images analysed were
captured approximately two hours after the initiation
of the OPV trial (Figure 7). During the oil emulsion
release operation from KV Sortland, the vessel
maintained an almost constant trajectory with a Course
Over Ground (COG) of 10°T and a Speed Over Ground
(SOG) of about 2 knots. After two hours, the oil
emulsion release was stopped, allowing for
observation of the full spatial extent of the oil streak
within the radar's coverage area.
X-band and Ka-band radar images were time-
integrated over a period of 1 minute to enhance the
discrimination performance of the oil slick against sea
clutter. Longer integration periods were not
considered, as the navigation sensor errors associated
with the ship's own motion compromise radar image
stabilization, leading to performance degradation over
extended integration times.
Figure 7 displays radar images of the oil spill: the
Ka-band radar image is shown on the left, while the X-
band radar image is on the right. A closer analysis
reveals damping areas behind the targets illuminated
by the radar. These sectorial areas result from beam
shading effects caused by the physical dimensions of
the targets obstructing the radar beam. If not properly
managed, these areas may lead to false oil detections
(false alarms). To mitigate this issue, automatic oil spill
detection (OSD) processors typically apply sectorial
inhibition masks behind the position of large targets.
The tracks of these targets are, usually, provided to
OSD systems by ARPA tracking systems or AIS
receivers.
Figure 7. NOFO OPV 2018 Oil Spill PPI Radar Integrated
Images (6 km range scale): Ka-band (left) and X-band (right)
Analysis of the integrated radar data revealed that
the oil emulsion formed a long, narrow streak with a
total range extent of about 5.5 kilometres. The width of
the streak varied from 100 to 400 meters, resulting in a
total affected surface area of approximately 1.98 km
2
.
Figure 8. The three measurement areas superimposed on the
oil spill shape polygon (Ka-band radar)
To evaluate the impact of the oil spill on the X-band
and Ka-band radar signals, three measurement areas
are selected within the spill region. These areas are
positioned at different grazing angles.
To normalize the measurements from the two
radars and assess the difference in damping over the
oil slick, the mean clutter reflectivity, 𝜎0 , is considered.
The surface clutter cross section, 𝜎c (m
2
), of a patch
defined by the intersection at the earth’s surface of the
azimuth beamwidth with a range gate at a range R (m)
is calculated using the radar equation [11]:
( )
3
44
22
4
r
c
t pc
R P LF
PG G
=
where Pt is the transmitted peak power (W), Pr is the
received power (W) from the surface clutter patch, G is
the antenna gain, Gpc is the pulse compression gain, λ
is the radar wavelength (m), F is the pattern
propagation factor that incorporates the effects of the
antenna pattern and the radar environment. 𝐿 is a
series of loss factors:
2
,t q bs r r m
L L L L L L=
In which:
L
t
is transmitter loss,
L
r
is radome loss,
Lbs is antenna beamshape loss,
L
q
is ADC quantisation loss,
L
r,m
is receiver mismatch loss.
The mean clutter reflectivity, 𝜎0, is then calculated
from the clutter cross section, 𝜎c:
0
c
A
=
In which A (m
2
) represents the area of the clutter
patch, being the product of its width and its depth [12].
Figure 9. Clutter patch area
2 cos
az
c
bs
c
AR
L


=

where 𝑐 is the speed of light (299792458 m/s), Rc is the
ground range (m), 𝜓 is the grazing angle, 𝜏 is the pulse
width of the compressed pulse (s).
Figures 10, 11, and 12 show the radar received
power (upper: Ka-band, lower: X-band) corresponding
to observation areas 1, 2, and 3, respectively, from
which the mean clutter reflectivity values are
calculated.
The various damping measurements of the oil slick
on capillary waves, measured using X- and Ka- band
radars, were found to be generally consistent across the
three observation areas and they are reported in
Table 5.
83
In the first observation area, positioned at a grazing
angle between 0.25° and 0.32°, the mean clutter
reflectivity difference between the oil dumped area
and the clean sea surface averaged -4.7 dB for the Ka-
band, while the X-band radar exhibited a difference of
-2.7 dB. In the second observation area, with a grazing
angle between 0.32° and 0.44°, the mean clutter
reflectivity difference for the Ka-band averaged -4.9
dB, whereas the X-band radar exhibited a difference of
-2.5 dB. Finally, in the third observation area,
positioned at a grazing angle between 0.45° and 0.85 °,
the mean clutter reflectivity difference for the Ka-band
averaged -4.8 dB, while the X-band radar exhibited a
difference of -2.5 dB.
Table 5. measured average oil damping on sea clutter
reflectivity
Area
Number
Grazing
Angles
Mean Clutter
Reflectivity
Difference on Oil
Damping (Ka-band)
Mean Clutter
Reflectivity
Difference on Oil
Damping (X-band)
1
0.25° to 0.32°
-4.7 dB
-2.7 dB
2
0.32° to 0.44°
-4.9 dB
-2.5 dB
3
0.45° to 0.82°
-4.8 dB
-2.5 dB
According the analysis, the X-band radar exhibited
an average damping on the clutter reflectivity ranging
from -2.5 dB to -2.7 dB, while the Ka-band radar
showed a damping between -4.7 dB and -4.9 dB.
Consequently, the Ka-band demonstrated an
additional advantage ranging from -2 dB to -2.2 dB. It
should be noted that this advantage was evaluated
under the conditions recorded during the NOFO OPV
2018 trial, characterized by wind speeds between 16
and 21 knots and a thin oil film resulting from the
utilized oil emulsion, [13].
Figure 10. MEASUREMENT AREA 1 – Radar received power
on sea surface affected by oil spill (Upper: Ka-band, Lower:
X-band)
Figure 11. MEASUREMENT AREA 2 – Radar received power
on sea surface affected by oil spill (Upper: Ka-band, Lower:
X-band)
Figure 12. MEASUREMENT AREA 3 – Radar received power
on sea surface affected by oil spill (Upper: Ka-band, Lower:
X-band)
The differences observed between the two radars
are not limited to the damping effect on the capillary
waves by the oil spill. Additional differences emerge in
their ability to discriminate thin oil streaks. This
discrimination capability is strongly influenced by the
higher resolution of the Ka-band radar, which proves
to be one of the most critical parameters for this type of
sensor designed for oil spill detection. These
differences in discrimination are clearly visible in
Figure 13, where it is reported the radar image (upper
image: Ka-band, lower image: X-band) of the oil spill
after about 22 hours after the oil emulsion release.
Here, the Ka-band radar successfully distinguishes
84
thin oil emulsion streaks as narrow as less than 15
meters.
These performance characteristics become
particularly important as the oil spill evolves over time,
causing its geometric shape to become less regular and
more fragmented, with thin oil streaks emerging that
are difficult to detect using low/medium resolution
radar systems. Under these conditions, a high-
resolution radar like the Ka-band radar used in this
study enables more accurate and efficient execution of
critical oil spill dispersion operations.
Figure 13. Differences on oil patches discrimination (Upper:
Ka-band, Lower: X-band)
6 CONCLUSIONS
This study demonstrated that Ka-band radar
outperforms X-band radar in oil spill detection during
the NOFO OPV 2018 trial, offering higher contrast,
finer resolution, and greater sensitivity to thin oil
layers and capillary wave damping. Ka-band data
showed nearly 2 dB greater sea clutter damping than
X-band, confirming previous findings and enabling
more precise spill delineation.
However, Ka-band’s performance is limited by
adverse weather conditions, where X-band radar
remains more reliable. The complementary strengths
of both bands, as integrated in the GEMINI-DB dual-
band radar system, provide a robust, all-weather
solution for vessel traffic service (VTS) operators,
enhancing early spill detection and response.
Future work should develop automated detection
algorithms, optimize dual-band parameters, and
integrate radar with other sensors to further improve
oil spill monitoring and environmental protection.
REFERENCES
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