Maritime Navigation and Communications Services

                              DGPS Testing for USCG - Biorka, Alaska                              

At LBA, we manufacture an unsurpassed line of shore transmitting and receiving antennas for all these services. We can supply all of the other equipment required for most shorestation applications.

With over 40 years experience in LF, MF, and HF transmission worldwide, we can design, furnish, install, and maintain virtually any type shore system anywhere in the world.

Critical operations in the MF and HF bands are typically associated with the communications requirements of the GMDSS, as well as traditional radiotelephone communications. The MF and LF bands are also used to support DGPS and LORAN navigation systems.

Below is a brief view of the various LF, MF, and HF modalities currently in use, andtheir technical outlines. We also provide convenient links to LBA products and services, and other resources useful to the maritime systems planner or manager.

An Overview of the Global Maritime Distress & Safety System

Since the invention of radio at the end of the 19th Century, ships at sea have relied on Morse code, invented by Samuel Morse and first used in 1844, for distress and safety telecommunications.

Over fifteen years ago the International Maritime Organization (IMO), a United Nations agency specializing in safety of shipping and preventing ships from polluting the seas, began looking at ways of improving maritime distress and safety communications.

This resulted indevelopment by IMO of a Global Maritime Distress and Safety System (GMDSS) to provide the communication support needed to implement the search and rescue plan. This new system is based upon a combination of satellite and terrestrial radio services, and has changed international distress communications from being primarily ship-to-ship based to ship-to-shore (Rescue Coordination Center) based.

It spelled the end of Morse code communications and provides for automatic distress alerting and locating.

Communications Requirements for GMDSS Sea Areas

GMDSS sea areas serve two purposes: to describe areas where GMDSS services are available, and to define what GMDSSships must carry.

Prior to the GMDSS, the number and type of radio safety equipment ships had to carry depended upon its tonnage. With GMDSS, the number and type of radio safety equipment ships have to carry depend upon the areas in which they travel.

The GMDSS consists of many separate systems the use of which depends upon the ship's sea area of operation. An array of radio navigation systems is also available to the mariner. Some of the principle systems which utilize the LF, MF, and HF bands are discussed further here.

 Digital Selective Calling (DSC) Systems

MF/HF radiotelephone service is offered to mariners as part of the GMDSS.

This service, called digital selective calling (DSC),allows mariners to instantly send an automatically formatted distress alert to the local Coast Guard or other rescue authority anywhere in the world. Digital selective calling also allows mariners to initiate or receive distress, urgency, safety and routine radiotelephone calls to or from any similarly equipped vessel or shore station, without requiring either party to be near a radio loudspeaker.

DSC acts like the dial and bell of a telephone, allowing you to "direct dial" and "ring" other radios, or allow others to "ring" you, without having to listen to a speaker. New VHF and HF radiotelephones have DSC capability.

 NAVTEX Alerting System

NAVTEX is an international, automated system for instantly distributing maritime navigational warnings, weather forecasts and warnings, search and rescue notices and similar information to ships.

A small, low-cost and self-contained "smart" printing radio receiver installed in the pilot house of a ship or boat checks each incoming message to see if it has been received during an earlier transmission, or if it is of a category of no interest to the ship's master.

A new ship coming into the area will receive many previously-broadcast messages for the first time; ships already in the area which had already received the message won't receive it again. No person needs to be present during a broadcast to receive vital information.  
 

Differential GPS (DGPS) Service

The DGPS Service broadcasts correction signals on marine radiobeacon frequencies to improve the accuracy and integrityto GPS-derived positions.

The US Coast Guard DGPS Service, for example, provides 10-meter accuracy in all established coverage areas. Many nations are implementing standard DGPS services modeled after the U.S. Coast Guard’s system to significantly enhance maritime safety in their critical waterways.

The US maritime DGPS service provides integrity alarms for GPS and DGPS out-of-tolerance conditions within 10 seconds of detection, availability of 99.7% per month, coastal coverage to the continental United States, the Great Lakes, Puerto Rico/US Virgin Islands, and selected portions of Alaska and Hawaii.

Typically, the positional error of a DGPS position is 1 to 3 meters,greatly enhancing harbor entrance and approach navigation.

 In addition, the US Coast Guard has extended the DGPS system to redundantly cover most of the continental United States in its Nationwide DGPS (NDGPS) program.

LORAN-C Navigation Service

LORAN-C was originally developed to provide radio navigation service for U.S. coastal waters and was later expanded to include complete coverage of the continental U.S. as well as most of Alaska.

Twenty-four U.S. LORAN-C stations work in partnership with Canadian and Russian stations to provide coverage in Canadian waters and in the Bering Sea. LORAN chains also operate in Europe and other parts of the world.

LORAN-C provides better than 0.25 nautical mile absolute accuracy for suitably equipped users within the published areas.

LORAN-C is approved as an en route supplemental air navigation system for both Instrument Flight Rule (IFR) and Visual Flight Rule (VFR) operations. It serves to also provide a host of other navigation, location, and timing services for both civil and military air, land and marine users.

3400 Tupper Drive (27834), P.O. Box 8026
Greenville, North Carolina 27835
800-522-4464 / 252-757-0279 / Fax 252-752-9155
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