Sonar & the USCG

By Dennis Bryant
Friday, March 07, 2014
A civilian contractor steadies a M18 Mod 2 Kingfish Unmanned Underwater Vehicle (UUV) as it is lifted with a crane onto the deck of an 11-meter rigid-hull inflatable boat. (U.S. Navy photo by Mass Communication Specialist 2nd Class Blake Midnight/Released)

The USCG Plans to Widen its use of the subsea surveillance technology. The question is: is the investment warranted?
 

The U.S. Coast Guard is planning to widely use sonar to support its maritime security and marine environmental protection missions. The agency currently has limited capability to detect objects below the water’s surface and relies on others (such as the U.S. Navy or the commercial sector) when such detection is needed.
Sonar is an acronym for Sound Navigation and Ranging.  The principle is similar to radar, used in the atmosphere. While radar uses radio waves, sonar relies on sound waves, which propagate much better than radio waves do in water.  There are two major types of sonar – passive and active.  Passive sonar only listens, detecting sounds made by vessels, persons, fish and other things in the water, or the water itself (e.g., waves).  Active sonar transmits a sound signal that then is reflected off an object within range and returns to the transducer.  Measuring the time difference between transmission and reception provides an indication of the range of the target.  Measuring the angle of the received signal provides an indication of the direction of the target. 
Sonar transmissions are made in a variety of frequencies, depending upon the intended purpose.  Low frequency transmissions have the advantage of very long range.  On the other hand, these sonar transmissions can only detect very large objects and with minimal accuracy relative to range or bearing.  Mid-frequency transmissions have a range measured in miles and are able to detect objects such as submarines and large whales with good accuracy relative to range and bearing.  This is the type of sonar utilized almost exclusively by the military, having virtually no commercial application.  High frequency and ultra-high frequency sonar transmissions have a short range, but are able to detect small objects.  This type of sonar is utilized commercially and is the type under consideration by the Coast Guard.
Sonar in the form of echo-sounders has been utilized for years by ships to determine the depth of water under the keel.  A signal is transmitted straight down.  The signal reflects back when it hits the seabed.  The time difference provides the operator with an accurate measure of the depth.  More sensitive versions are in use as fish finders.  These devices differentiate between the strong signal generated by reflections off the seabed and weaker signals generated by reflections off objects in the water column.  Sophisticated versions provide more detailed information, allowing determination of the size of the fish school, etc.  Sonar transmitters can even be attached to trawl nets, allowing for better placement of the nets relative to the target species. Stronger and more sophisticated sonar can be used to penetrate the upper layer of the seafloor, allowing determination of characteristics such as bottom type (i.e., mud, sand, gravel) and depth to hard strata.  This information can prove valuable for determination of anchorage grounds and for laying of submarine cables and pipelines.
Sonar is used commercially to examine hulls, pilings and underwater structures such as offshore platforms.  This type of sonar is sometimes handheld by a diver or mounted on the end of a pole.  Increasingly, it is mounted on remotely operated vehicles (ROVs) or on unmanned underwater vehicles (UUVs).  ROVs have greater capabilities regarding power and data transmission, since they are tethered to a shore location or to a manned vessel.  UUVs have less power and data transmission capabilities, but can get into tighter spaces and have longer potential range.
Diver detection sonar is used for detection of divers and submerged swimmer delivery systems, such as those used in several of the James Bond movies.  This sonar provides detection, classification and tracking information on human underwater incursions that could endanger lives or property.  It is being employed around some marine facilities worldwide, but not yet to a great extent.  Limpet mine imaging sonar is used for detection of small underwater objects.  Originally used for detection of limpet mines potentially attached to the hulls of ships, it can now be used to detect caches of drugs and other contraband.  This type of sonar may also be used to detect hull damage and underwater structural damage.
The Coast Guard proposes to utilize commercially-available sonar equipment to broaden its capability to locate, image and classify submerged and underwater targets of interest (TOIs).  This would include such things as terrorist attacks and environmental threats (i.e., pipeline leaks).  This usage is aimed at protecting human safety, preventing property damage, and protecting the marine environment. 
Use of the sonar by the Coast Guard is envisioned as of short duration and within a limited geographic area.  For example, it might be used to protect a high-level dignitary during a visit to a waterfront facility.  Alternatively, it could be used to examine an offshore facility from which oil is emanating to determine the location and extent of damage or other cause of the discharge so that it can be promptly remedied. 
At least for now, the Coast Guard intends to utilize commercially-available sonar with frequencies above 50 kHz.  As a result the capabilities, limitations and potential adverse effects of equipment are reasonably well-known.  This, combined with the short duration and limited geographic scope of the sonar use, will serve to minimize any environmental impact.  Further, the Coast Guard proposes to consult with other agencies, such as the Fish and Wildlife Service (FWS) and the National Marine Fisheries Service (NMFS) prior to each planned use in all but emergency situations to determine whether there are particular environmental concerns that should be considered, such as endangered species in the vicinity.  The Coast Guard also plans to utilize observers to monitor usage and identify any unexpected risks, such as boaters or swimmers approaching the area. 
The sonar systems under consideration by the Coast Guard operate within the hearing range of toothed whales (150-180 kHz) and pinnipeds (75 Hz – 75 kHz).  Some clupeid fish (i.e., herring, shad, sardine, menhaden) may also react to these sonar transmissions.  Minor adverse impacts could also occur in the unlikely situation if a ROV or UUV were to touch down on seagrass, coral or sediment.  The use of low-power HF and UHF sonar (as opposed to high-power MF military sonar) minimizes adverse environmental impact by reducing the area ensonified by the equipment. 
The purpose of the Coast Guard proposal is to broaden the agency’s capability to locate and classify underwater threats and other targets of interest and to more safely and effectively accomplish the Coast Guard missions.  Targets of interest could include combat swimmers or divers; explosives or other offensive devices that could be delivered to underwater hulls, piers or other shore structures; and objects that have become submerged as a result of natural or man-made disaster and have the potential to interrupt maritime transportation, trade, commerce, recreational boating or other maritime activities.  The use of HF (50-999 kHz) and UHF (1,000 kHz and higher) active sonar technology would provide operational commanders with enhanced ability to support maritime security, marine safety, and maritime stewardship with minimal impact on the environment. The likelihood of a terrorist attack by divers in U.S. waters is extremely low.  More likely are suspicious incidents that require prompt investigation and response, similar to the various private pilots that negligently stray into restricted airspace around the White House.  It is expected that the Coast Guard will more frequently use sonar to investigate suspected contraband stashes affixed to the underwater hull of incoming vessels, marine casualties, hazards to navigation, and environmental threats.  Used properly, sonar can provide the Coast Guard with important new capabilities.

(As published in the March 2014 edition of Marine Technology Reporter - www.seadiscovery.com)

Maritime Reporter August 2015 Digital Edition
FREE Maritime Reporter Subscription
Latest Maritime News    rss feeds

Technology

Keppel Delivers Jackup to UMW-OG

Keppel FELS, a wholly owned subsidiary of Keppel Offshore & Marine (Keppel O&M) has delivered UMW Naga 8, a KFELS B Class jackup rig, to Malaysia’s UMW Oil & Gas Corporation Berhad (UMW-OG).

Subsea 7 Bags $150 million Offshore UK Contract Maersk

Offshore contractor Subsea 7 has been awarded a $150 million subsea, umbilical, riser and flowline (SURF) contract by Maersk Oil for the development of the Culzean field in the UK North Sea.

SMOE Wins $1bln Multi-platform Culzean Contract

Singapore's offshore services provider Sembcorp Marine has won an engineering, procurement and construction (EPC) contract worth over USD1 billion for the Culzean

Navigation

Draft Increase at Southwest Pass, Mississippi River

The draft for the Southwest Pass on the Mississippi River has been increased from 45 to 47 feet following dredging, Inchcape Shipping Services (ISS) is advising.

USCG Rescues Unconscious Boater

The Coast Guard rescued an individual from a marsh flat in Barataria Waterway located approximately six miles north of Grand Isle, Tuesday. Coast Guard Sector

Worldwide Launch of Joint CIC

The Maritime Authorities of the Tokyo and the Paris Memoranda of Understanding (MoU) on Port State Control has launched a joint Concentrated Inspection Campaign

Finance

Dry Bulk Recovery Still a Long Way Off

The dry bulk shipping market will remain in recession due to contracting demand for iron ore and coal, and any recovery is not expected until 2017, according to

Egypt Picks Jordan LNG Cargo Winners

Egypt has picked Shell, Vitol and Trafigura in a tender to supply four cargoes of liquefied natural gas (LNG) via Jordan's Aqaba import terminal, trade sources said.

Cameroon Awards Kribi Deepwater Contract

Cameroon has awarded a contract for its Kribi port to a consortium led by French logistics group Necotrans, the two parties said. The deepwater port will allow

Maritime Security

Boat with 40 African Migrants Arrives on Spanish Island

A boat containing around 40 African migrants including a toddler girl landed on a beach on the Spanish island of Gran Canaria, sea rescue services said on Wednesday.

Twelve Syrians Drown Trying to Reach Greece

At least 12 people believed to be Syrian refugees drowned as two boats sank after leaving southwest Turkey for the Greek island of Kos on Wednesday, a senior Turkish naval official said.

Greek Coast Guard Seizes Weapons Ship Bound for Libya

Greek authorities have seized a freighter carrying an undeclared shipment of weapons en route from Turkey to Libya, coast guard officials said on Wednesday. A

News

Dry Bulk Recovery Still a Long Way Off

The dry bulk shipping market will remain in recession due to contracting demand for iron ore and coal, and any recovery is not expected until 2017, according to

New Cutter Suction Dredge: Modern and Efficient

Ellicott Dredges, LLC has debuted a new design 20” (500 mm) cutter suction dredge, the Series 2070 Dragon dredge.    Aiming to take advantage of modern, up-to-date

Boat with 40 African Migrants Arrives on Spanish Island

A boat containing around 40 African migrants including a toddler girl landed on a beach on the Spanish island of Gran Canaria, sea rescue services said on Wednesday.

Coast Guard

Twelve Syrians Drown Trying to Reach Greece

At least 12 people believed to be Syrian refugees drowned as two boats sank after leaving southwest Turkey for the Greek island of Kos on Wednesday, a senior Turkish naval official said.

Greek Coast Guard Seizes Weapons Ship Bound for Libya

Greek authorities have seized a freighter carrying an undeclared shipment of weapons en route from Turkey to Libya, coast guard officials said on Wednesday. A

Singapore Navy Foils Pirate Attack

The Republic of Singapore Navy ( RSN) disrupted a sea robbery on a tugboat in the eastern approaches of the Singapore Strait, says Ministry of Defence (MINDEF).

Subsea Defense

Japanese Sub Pitch puts off Australian Firms

Japan had been seen as frontrunner for Australian submarine deal, but Australian defence firms unhappy after talks with Japan. A Japanese consortium eyeing a A$50 billion ($35.

Britain Pumps GBP500mln into Scottish Naval Base

The Royal Navy’s submarine base at Faslane – home to Britain’s nuclear deterrent – is to receive a more than 500 million pounds investment grant from the Government, reports Reuters.

Russian-Chinese Naval Drills End

The second phase of the Russian-Chinese Joint Sea-2015 naval maneuvers has officially ended outside the port of Vladivostok in Russia’s Far East, says spokesman

 
 
Maritime Careers / Shipboard Positions Maritime Standards Naval Architecture Offshore Oil Port Authority Ship Electronics Ship Repair Ship Simulators Shipbuilding / Vessel Construction Winch
rss | archive | history | articles | privacy | contributors | top maritime news | about us | copyright | maritime magazines
maritime security news | shipbuilding news | maritime industry | shipping news | maritime reporting | workboats news | ship design | maritime business

Time taken: 1.0776 sec (1 req/sec)