Читать книгу SELF-STEERING UNDER SAIL - Peter Foerthmann - Страница 14

Until a few years ago it was generally the case that boat owners acquired their instruments one by one. Depth sounder, radar, compass, wind instrument, Decca, GPS, plotter, boat speed indicator and autopilot might easily be individually installed stand-alone units from several different manufacturers.

The situation today is very different, with a few major suppliers offering complete systems from which the sailor can choose as few or as many instruments as desired. Essential to this advance was the development of a specialised data protocol (data bus): functions such as the steering performance of an autopilot module can now be optimised in more demanding systems by connecting a dedicated course computer. An autopilot steering a boat between two waypoints obtained from a GPS interface can thus correct for cross-track error caused by currents running perpendicular to the boat’s course.

The changing role of companies within the industry from instrument manufacturers to system suppliers explains the current extreme concentration of the market on just three major players.

Autopilots may be divided into three groups:

a. Stand-alone systems which operate solely on the basis of a windvane or compass signal (e.g. AUTOHELM 800),

b. Systems which are linked to other modules via a data bus (e.g. SEATALK from Autohelm, NETWORK from B&G),

c. Intelligent systems in which the data of the individual modules is optimised by a relatively powerful computer (e.g. ROBERTSON AP 300, AUTOHELM 6000/7000, B&G HYDRA/HERCULES).

Module integration options with ROBERTSON

Today most autopilots operate as one module within a complex system. NMEA (National Marine Electronics Association) interfaces offer the prospect of expanding such a system to include instruments from other manufacturers. In reality, however, the claim that instruments from different system suppliers can communicate with each other using the same interfaces has proven to be something of a fallacy. There are, as many sailors have already discovered to their cost, several standards in existence even for NMEA interfaces. Of course no instrument manufacturer is to blame for any incompatibility; serious communication problems are always the fault of the instrument on the other side of the interface!

Provided with a fluxgate compass signal optimised by integrated navigation modules, an autopilot is perfectly capable of steering a boat from waypoint to waypoint - assuming of course that the wind decides to cooperate.

Navigating down below with the AUTOHELM NAVPLOTTER 100