Furuno’s new satellite compass

This is a fully solid state compass that delivers heading information that is accurate to 0.4° which is much better that of magnetic or gyro compasses. In addition, this compass can provide a wide range of other information based on the satellite positioning such as speed over the ground, rate of turn and pitch, roll and heave data. Whilst this level of information may not be required in normal workboat operations it can be vital for survey and other operations where data from soundings or sonar can depend on the movements of the vessel. The accurate and stable heading information can improve the stability of radar targets when the radar is being used for collision avoidance.

Satellite compasses work by comparing the position information generated by two adjacent GPS antennae. The SC33 measures and compares the very slight time differences between the two antennae which are situated just 30cms apart in the compass antenna. This information can be displayed in a number of ways including a traditional compass display and it can also be transmitted to other equipment via NMEA connections. Unlike heading information generated from a conventional satellite receiver the SC33 can still produce heading information when the vessel is at zero speed. “The underlying technology is the phase relationship between the two antennae”, commented Eric Kunz, Furuno’s senior product manager. “The SC33 compares the slight time differences that are measured in billionths of a second.”

In addition to operating on the signals from the US GPS system, this new compass can also operate using the Russian Glonass, the European Galileo and the Japanese QZSS satellite systems which act as a good backup.

The two antennae are housed in a sealed rectangular radome type unit that weighs 2.5 kilos. This should be mounted high in the vessel with a clear view around the horizon. Selecting a good mounting position can prevent multipath signals reflected from surfaces on the boat and Furuno can also supply bird repellent systems to prevent fouling on the antenna.