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Underwater Security and Surveillance

Introduction

Underwater Security addresses the protection of land facilities and valuable assets that are vulnerable to attack from the waterside. Attacks may take the form of armed combat divers or the use of explosives against target vessels or facilities. A complete Underwater Security program also includes examining ships for contraband containers fixed to the hull.

Techniques commonly used are underwater video cameras and acoustics (sonar). In most harbors underwater vision is extremely limited. Sonar, however, is not limited by optical conditions.

Scanning sonar can be used to sweep or "clear" areas to ensure they are clear of foreign objects such as mines, Improvised Explosive Device - IEDs, or contraband. Multibeam sonar can be used to detect the presence of divers, whether in a secure area within a defined perimeter or an underwater area under surveillance for law enforcement purposes. Sonar altimeters may be used to create an "acoustic fence", providing an alert for further investigation.

Kongsberg Mesotech Ltd. is a leader in the development of scanning and multibeam sonar and its application to all facets of underwater security. Applications for sonar can be classified into these categories:

Diver Detection

Diver Detection or Underwater Surveillance, as it is also known, is a complex and challenging task due to limitations placed on various technologies by the subsea environment. A white paper prepared by Kongsberg Mesotech explores the different approaches and their effectiveness.

Effective ranges for diver detection are from 400 meters to greater than 800 meters, depending on a variety of factors. Underwater Intruder systems will operate on a range scale of 800 meters in order to provide the longest possible alert time, thereby enabling an effective response. Due to the detection range involved, divers are represented by icons on the display. The capability to view a sonar image for confirmation can be provided through "zoom" capability on the sonar system, or through a mobile sonar or underwater video system deployed using a boat or ROV.
 


The above video has been reduced to be playable on web. To view the video at full resolution use the link below - file size about 27MB.


At ranges less than 200 metres, a higher frequency sonar can be employed that will also enable confirmation at close ranges. This example demonstrates detection of Surface Swimmers.
 

The above video has been reduced to be playable on web. To view the video at full resolution use the link below - file size about 105MB.

 

Hull Inspection

Ship hulls are scanned to determine if explosives or contraband (usually narcotics) have been attached. Magnetic mines may be attached anywhere to a steel hull below the waterline. Containers for smuggling narcotics are often secured to bow thrusters or rudder structures. Clearance divers are typically used to search the hull for mines or containers, a time consuming and difficult process, particularly in limited visibility. High Resolution Scanning Sonar can examine a ship's hull in a short period of time and is able to resolve raised objects on the hull only a few centimetres high. When properly deployed, details as fine as weld seams are visible as shown in this scan.

Hull Scan of Barge - Click to view larger image
   Hull Scan of Barge - Click to view larger image.


Scanning sonar is positioned most easily by using an ROV with sufficient power to hold against currents and to press the structure of the ROV against the hull. This provides a steady platform for the high resolution scanning sonar and enables high quality scans that readily define features such as this small container attached to a ships hull.

Small container attached to a ships hull - Click to view larger image
   Small container attached to a ships hull - Click to view larger image


The KONGSBERG MS1000 scanning sonar is an ideal solution for vessel hull inspection. This high resolution sonar is capable of rendering complete vessel hull imagery that can detect foreign objects down to several centimetres. The sonar is lightweight, hand portable, and provides imagery on a laptop computer. It can easily be used by a single person to perform a complete bow – to stern vessel hull inspection and present data as a single (mosaicked) image that provides a complete view of the submerged portion of any vessel. Vessel inspections can be completed in far less time than diver searches with little or no risk. Merging the scans together using a KONGSBERG software package can provide a complete picture of the ship’s hull, verifying the areas scanned are clear, and documenting that areas have not been missed.

Bow to stern vessel hull inspection
  Bow to stern vessel hull inspection.

Berth Clearance

High Resolution Scanning Sonar can examine a ship’s berth in the greatest level of detail to determine if a berth is clear of objects that could represent a threat to a visiting warship, cruise liner or other high value asset. Berth inspections can be conducted in real time and comparisons made to previous scans in post processing using commercial software packages or KONGSBERG 's KeyPoint TM image processing software.

Sonar imagery is obtained in real time using a portable laptop computer equipped with the MS1000 software. A single person can easily provide a complete security inspection of a vessel pier and the surrounding underwater terrain by performing an interlocked series of scans. The sonar head can be oriented to provide horizontal coverage (for the seafloor near the pier) and may be vertically oriented to provide vertical coverage for inspection of pier walls.

A single person can easily provide a complete security inspection of a vessel pier and the surrounding underwater terrain
   Complete security inspection of vessel pier and surrounding underwater - Click to view larger image

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