header

Boat Electronics - Navigation and Marine Radio Systems Overview

Electronic & GPS Navigation Marine Radio - VHF, Single Sideband, Inmarsat C and Navtex Radars EPIRB

Yacht electronic systems and boat electronics navigation system includes decca radio navigation system and gps navigation Marine Radio Communication - VHF, Single Sideband, Inmarsat C and Navtex boat electronics. Navigation radio systems.

The microelectronics evolution has affected most of every part of daily life, including life aboard ship, where a variety of boat electronics makes life easier for the mariner. The three main areas to benefit from this are navigation, communication and safety.

Electronic Navigation Systems - GPS Navigation

Up to 1990, there were a number of boat electronic navigation systems available in the marketplace, such as Loran, Decca, satnav (satellite navigation) and RDF (radio direction finding), but since the American Global Positioning System (GPS) has been available to the public it has come to dominate. Originally developed as a military system, GPS consists of a constellation of satellites that between them provide worldwide coverage 24 hours per day.

Global Positioning System - GPS Navigation System

Global positioning system (GPS) receivers calculate position using information from a network of satellites and are accurate to within 100m (300ft). The GPS navigation system is actually more precise, but the service provided to civil users is deliberately downgraded for military security purposes. Enhanced, Differential GPS navigation units (DGPS) are accurate to within 10m (30ft) and provide a digital readout in latitude and longitude or as a bearing and distance from a chosen site. The latter is often easier to use for plotting position.

Receivers can also be programmed with 100 or more waypoints which are positions of charted objects or turning marks on the course. Boat GPS navigation systems usually have other functions calculating useful information about progress and course sailed.

Available hand-held GPS navigation sets, being affordable with accurate positioning, has made all other systems relegated to standby status in case the GPS suffers a breakdown or the US Government turns it off. The Decca system is expected to be withdrawn in the near future, leaving Loran as the main standby. More sophisticated instrument sets receive both GPS and Loran.

This has changed the style of navigation, with the most basic boat GPS systems being able to store a number of waypoints. When selecting a waypoint, the set tells you its distance from your position, its bearing, and the time needed to reach it at present speed, so a coastal passage becomes a string of waypoints that are in turn selected.

The almanac publishers now give the latitude and longitude of hundreds of seamarks and coastal features so they can be quickly loaded as waypoints without the need to plot them on a chart.

The next stage does away with paper charts entirely by replacing them with CD-ROM discs which display the chart on a screen. Each chart can also be overlaid onto a radar display while a cursor can be moved around the screen to pick off and display the waypoints.

Another electronic navigation system is the chart plotter which displays an electronic chart on a screen allowing the chart to be scrolled and can be worked on as on paper. A chart plotter and GPS combination is connected to an electronic self-steering system which directs it to steer between waypoints on the electronic chart, using GPS information keeping the boat on course.

Marine Radio Communication - VHF, Single Sideband, Inmarsat C and Navtex

Communication with other vessels, or with coastal radio stations, is universally carried by VHF radiotelephone. Open boats with no power supply can carry a hand portable set with all the marine channels and a 10 miles range. This is a valuable safety aid and coastal radio stations provide the means of linking into the normal telephone system. Mobile phones, which often give a range of 20 miles or more over water now offer this service.

Radio communication over a longer range consists of two alternatives: HF (high-frequency) radio, also called SSB (single sideband), and satellite. HF radio can give worldwide range but the sets are expensive and training is needed to obtain an operator's licence.

Satellite communication (or satcom) using the Inmarsat system is rapidly growing in popularity but both the equipment and the calls are expensive. A lower cost alternative for sailing yachts is Inmarsat C, which transmits text but not speech and requires only a small inmarsat antenna.

A very special quality of Inmarsat satellite phone is, that the set can be 'polled' from a shore station and will respond by giving its position, obtained from GPS navigation unit. In an emergency, the crew of a yacht can press a 'panic button' causing the Inmarsat to transmit an automatic distress call accompanied by the boat's position.

A useful aid is the Navtex receiver, which receives weather and safety information and prints it out. The benefit of the Navtex system is that there is no risk of missing an important message such as a gale warning.

Marine Radar

Radar can now be found on many small yachts though the basic fact that range depends on the height of the antenna above the sea. But both the size and the price of sets have fallen, as has the power requirement, while the picture quality has improved. On boats larger than 11m (35ft), radar is a useful electronic aid, and has position-fixing and collision-avoidance capabilities. Attend a course to learn to use radar to its fullest extent.

A radar set has a display screen linked to an antenna that transmits signals then receives radar reflections from the shore, buoys, or other vessels. A bearing and distance between the yacht and the objects is displayed on the screen and if marked on a chart, the range and bearing can be used to plot the boat's position. Radar is more accurate determining range than bearing so radar fix uses three ranges of charted objects. If the fix is another vessel, the course and speed can be determined and whether it represents a collision risk being useful in restricted visibility.

Maritime EPIRB

There are other devices that are exclusively concerned with safety being the EPIRB (Emergency Position Indicating Radio Beacons), a very robust automatic distress beacon whose signals are picked up by satellites, aircraft and shore stations.

Ships and fishing vessels have to carry an EPIRB that automatically floats clear and begins sending if the vessel sinks. Yachtsmen carry the miniature version that can be sewn into a foul-weather jacket or carried in a pocket. In addition to sending a distress signal, the device transmits a code identifying the user while the COSPAS-SARSAT satellites pin down EPIRB’s position to within about a square mile.

Tiny beacons, made by both Sea Marshall and Jonbuoy, are worn on foul-weather clothing, and sound the alarm if the wearer falls overboard. The signal acts as a homing beacon to help find the person in the water and causes the boat's GPS set to mark the position as a waypoint.

GPS Navigation and Inmarsat C radio communications along with maritime radar and EPIRB are yacht electronic systems.