Satellite Compass Service Providers

A satellite compass gives true heading from GNSS with no gyro to spin up and no deviation to correct, but it only reads right if the antenna is sited and aligned correctly and the system is kept current. Satellite compass services cover that side of the work: installation and alignment of the antenna, the offset and configuration that make the heading true, software and firmware upkeep, interfacing to the bridge systems that use the heading, and fault diagnosis and repair.

Installation and the Antenna

The antenna unit decides everything. It has to be mounted with a clear view of the sky, away from radar beams, satellite communications antennas, and structures that reflect signals and cause the multipath errors a heading sensor cannot tolerate, and its fore-and-aft line has to be aligned to the ship's head with the heading offset entered so that the compass reads the ship's real heading and not one a few degrees out. On units with separate antennas the baseline length and orientation are measured and entered as well, and the offset is set against a known bearing, a transit or the ship's gyro alongside, so the reading is proven rather than assumed. Getting the siting and the offset right is the difference between a compass that holds heading and one that wanders or drops out, and it is the step that most rewards an experienced installer.

Software, Interfacing, and Repair

A satellite compass is usually the ship's transmitting heading device, feeding heading to the radar and ARPA, the AIS, the ECDIS, and the autopilot, so part of the service is proving that each of those reads the heading correctly over the standard IEC 61162 interface and that the compass still meets its type approval as a transmitting heading device under IMO Resolution MSC.116(73), the record a nav survey looks for. Firmware is kept current for the GNSS constellations and corrections it uses, and where the reading has failed an engineer traces the fault between the antenna, the cable, and the processor rather than swapping blind, drawing on ordinary satellite compass spare parts. Because it depends on the satellite signal, a compass that loses heading is checked for jamming, blockage, or a failed antenna, not only for a broken box.

A satellite compass is often looked at in the same visit as the gyro and magnetic compass and the autopilot, since one team keeps the whole heading chain honest, and where a heading source is past repair a replacement is fitted and aligned by the same people. Compare the satellite compass services below by service area and class approval, and give priority to the ones with the maker training to align and commission a heading device, not only to change a display.