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Benefits and limitations of marine radar for wide area security surveillance

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Introduction

The purpose of this white paper is to examine the benefits and limitations of shore based marine

radar for waterside security applications. This technology has been deployed for over 60 years inVessel Traffic Service (VTS) systems, and is more recently being used in security applications.

When radar is combined with tracking and rule processing software in a security system, widearea surveillance can be automated, allowing facilities to effectively enhance waterside

surveillance and meet the intent of security regulations without increasing their security staff size.

Radar Based VTS Systems

Marine radar has been used on land for VTS systems since 1948, when the first system wasdeployed in Douglas, Isle of Man. Several months later, trials were conducted in Rotterdam, and

once the technology was proven, a number of European ports deployed radar based VTS systems

in the 1950s. Today there are over 500 VTS systems in service globally. The VTS industry hasgiven us much insight into the strengths and limitations of shore based radar as applied tosecurity systems.

Figure 1: VTS test site in Rotterdam, 1948. Source: Photo collection D. Zwijnenburg, VTS Manual 2002

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Benefits and limitations of marine radar for wide area security surveillance

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Radar Based Security Systems

In the past 10 years as the interest in port security has increased, shore based marine radar is also

 being deployed in wide area surveillance systems. Some of the larger companies providing thesesystems are L-3, Lockheed Martin, and Honeywell. Smaller companies like Observation

Technologies and SSR are also deploying some systems, and VTS companies such as Tidelandand Kongsberg are repositioning their VTS systems toward security solutions. The number of

shore based radar security systems is much smaller, but substantial growth is seen in the next 5 to10 years as an efficient alternative to waterside surveillance using solely video analytic solutions.

A common question by ports is “can we use our VTS radars for security?” The answer is that

it’s not practical to do so, because the missions of security and VTS are different, and so thesettings of the radar need to be different as well. Even if a compromise configuration were

implemented to support both, both VTS operators and security personnel need to have the option

of changing the configuration to respond to a situation, which may impact the other mission.

Benefits of Radar Based Waterside Security Systems

The primary benefits of a radar based waterside security system are 1) automation of wide areasurveillance, 2) improved surveillance effectiveness over other technology such as CCTV, and 3)

cost savings in personnel, equipment, and maintenance. Each of these benefits will be addressed below, as will system requirements needed to achieve them.

 Au tomation o f Wide Area Surveil lance

Automating surveillance is a force multiplier for a security team because the system works 24hours a day, 7 days per week to monitor selected areas and only alerts an operator when there is a

 potential threat. The radar itself will not provide this benefit, however. The radar data must be processed to filter out noise and to determine when there is a potential threat. Once a threat has

 been identified, an operator needs to be alerted, and the information needed to assess the threatneeds to be presented to the operator. Typical components of such a system are shown in figure

2 below.

Radar

Sensor   Tracker 

  Rule

Processor 

Display

System

 Alarm

Response

CCTV

Response

 AIS

Radar

Sensor   Tracker 

  Rule

Processor 

Display

System

 Alarm

Response

CCTV

Response

 AIS

Fi ure 2: Data flow of an automated surveillance s stem

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 Radar Sensor

The radar sensor is marine radar that is modified for waterside surveillance. The powerof the radar can range from 4KW to 25 KW, and the waveguide length of the antenna can

range from 6 to 9 feet or more. The radar must be equipped with hardware to convertradar video data to raw image data that can be transmitted to tracker software over a

network.

Tracker

The tracker software is a component of the system that receives raw radar data and

extracts the radar returns that are most likely to be objects of interest. Returns that arefiltered out may be from land, structures, waves, and birds. Returns that are typically of

interest are from boats. Important features that tracker software must have in order to provide this processing are the ability to:

  Define an area of interest  Exclude reflections from land

  Define the number of returns required to start or stop a track

  Allow the operator to tune the radar

  Send track data to a rule processor

 Rule Processor

The rule processor receives track data from the tracker, and decides which of the tracksmay be a threat. This decision process is based on user defined rules, which allow the

system to differentiate between normal activity and potential threats. One rule may bethat if a vessel has an AIS transponder, that it is not a threat. The rule processor must

also be able to send data to a display system to generate an alarm and to initiate a cameraresponse other wise known as “slue to queue.” A summary of rule processor capabilities

is:

  Ingest track data from one or more radar sensors

  Ingest data from an AIS receiver

  Prioritize track data based on user defined rules

  Send display data to the display system

  Create an alarm response when a threat is determined

  Prioritize tracks and assign cameras to the threats

  Send camera pointing commands to the CCTV system

 Display SystemThe display system provides situational awareness to the operator, usually by showing potential threats and CCTV images over a reference image or map. In this way the

operator can see the location and movement of threats, and can quickly assess them witha live CCTV image.

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 Alarm Response

The alarm response component receives alarms from the rule processor and displays thealarm to the operator. The alarms are stored and sorted, and in some systems can initiate

an automated response.

CCTV Response

The CCTV response receives camera control commands from the rule processor, and

uses them to automatically control one or more cameras to point to the threats.

Effect iveness of Radar vs. CCTV

CCTV surveillance has an inherent trade off between range and field of view. A typical securityCCTV camera may have a 45° field of view at wide angle, but a short detection range of 250

meters or less. The camera can be zoomed to support a range of say 1000 meters, but at that

range the field of view may be only 2°. A radar sensor does not have this trade off. Radars candetect small boats at long ranges, up to 6 or even 12 Nautical Miles (NM), and have a 360° fieldof view.

CCTV is often combined with Video Analytics (VA) to automate surveillance. While VA can

generate good results in controlled environments, it is not as effective in an outdoor wide area because of the changing lighting and sea state conditions.

While radar is more effective as a sensor because of these two trade offs, a pan tilt camera is still

required as an assessment tool. The radar and processors can detect and initially identify whatmay be a threat, but ultimately an operator must make a decision based on a CCTV image to

verify friend or foe. Radar can replace the detection cameras in a CCTV system, but not theassessment cameras.

Cost Savings of Radar Systems

An automated radar surveillance system can provide substantial savings in the cost of other

technologies in equipment, infrastructure, maintenance, and personnel.

Equipment costs are lower because one sensor can cover such a large area. For instance, a singleradar set to a modest range of 1 NM can cover a circle area of 3.14 square NM, or over 100

million square feet. A 1000 meter camera with a 2° field of view, on the other hand, will only

cover about 18 thousand square feet. Using this example, the radar can cover the area that over5000 cameras can. As a further example of the effectiveness of the coverage of radar in theexample below, 24 cameras were required for waterside surveillance coverage using video

analytics, but only one radar and one long range camera was required to effectively cover the port area depicted in Figure 3.

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Figure 3: Example of video analytic CCTV coverage vs. radar surveillance

24  Cameras for detection 1 radar for detection, 6 cameras for verificationPartial coverage Full coverage

Extensive set up, tuning Less set up and maintenanceLimited operations in weather and light 24/7 operations

Infrastructure costs are lower because fewer sensors are required, which mean power and

communications network components have to be brought to fewer locations. Maintenance is lesswith a radar system because if there are fewer sensors, less communications infrastructure to

maintain, and typically personnel costs are lower because an automated radar system will allow personnel to do tasks other than monitoring the security system until there is an alarm.

Limitations of Radar Based Waterside Security Systems

Limitations in a radar surveillance system are the same limitations in many electronic

surveillance systems. They are probability of detection, nuisance and false alarms, resolutionand discrimination, and dropped tracks.

Probability of Detection (Pd) is the probability that an object of a predefined size (say a small

 boat of 8M or larger) will be detected in an area of interest. Pd can be measured at several pointsin the data flow shown in Figure 2. There is a probability that an object will be in the raw data

sent from the radar to the tracker. This is controlled by the sensitivity settings of the radar.There is a probability that an object will be tracked by the tracker and sent to the rule processor.

This is controlled by the tracker settings and there is a probability that an object will cause therule processor to trigger an alarm. This is controlled by the rules that have been defined by the

user. For the purposes of this paper, System Pd is measured at the display system, meaning thatthe radar has to detect the object, the tracker has to track it, and the rule processor has to send it

to the display system.

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foe.

Turning False Alarm A fast turning boat can cause a newtrack to be formed if it turns fastenough to leave the area predicted

by the tracker.

This is not a commonoccurrence, but if it happens theinterrogation camera is still

pointed toward the boat and canbe manually adjusted if desired.

Dropouts Momentaryloss of track

Dropouts are common in all radarsystems and can increase if thesystem sensitivity is set too low or ifthe track parameters or incorrect.

 Alarms have been generatedand the camera is still pointed tothe object. Visual verification ofthe vessel’s presence has beenverified by the operator on thefirst alarm and can continue tobe monitored if the vessel is athreat

Resolution Mergedtarget

Two boats very close to one anotherproduce only one track.

If the boats are close enough tobe one track, then they aretypically close enough to be

captured in the same image.This is issue is mitigated by theoperator looking at the CCTVimage.

Hiding Missedtarget

 A smaller boat behind (parasiticvessel) a large one produces onlyone track.

It is possible for a smaller vesselto go undetected in thisscenario. The mitigation is touse CCTV cameras.

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References

BRIGGS, J. N.: ‘Target Detection by Marine Radar’ (The Institution of Electrical Engineers,

2004)

IALA AISM: ‘IALA Vessel Traffic Services Manual’ (VTS Manual, 2002)

SKOLNIK, M.I. (Ed.): ‘Radar Handbook’ (McGraw-Hill, New York, 1970)

ROHAN, P.: ‘Surveillance Radar Performance Prediction’ (Peter Perigrinus for the IEE, 1983)