Compass linearization — Evolution autopilots

The EV unit’s internal compass needs to compensate for local and the Earth’s magnetic fields. This is achieved using an automatic process known as linearization.

Initial linearization

Compass linearizationWhen the EV unit is first installed and powered-up (or after a factory reset or compass restart) linearization is required. A progress bar is displayed to indicate this:

The linearization process will start automatically after your vessel has turned approximately 100° at a speed of between 3 –15 knots. Linearization requires no user input, however at least a 270° turn is required before linearization can complete. The progress bar displays the progress, and will turn Red if the process is paused or otherwise interrupted. The time to complete linearization varies according to the characteristics of the vessel, the installation environment of the EV unit, and the levels of magnetic interference at the time of conducting the process. Sources of significant magnetic interference may increase the time required to complete the linearization process. Examples of such sources include: marine pontoons, metal-hulled vessels, and underwater cables.

You can speed-up the linearization process by completing a full 360° turn (at a speed of 3 – 15 knots). You can also restart the linearization process at any time by selecting the Restart Compass menu item.

Once the initial linearization is complete, the Deviation page is displayed and the current maximum compass deviation is shown:

Compass deviation

Compass deviationIf the reported deviation is 45° or higher, it is highly recommended that the EV unit is moved and re-installed in a location which is subject to less magnetic interference. After the linearization process has successfully completed you can check the current deviation value at any time from the Diagnostics pages.

Note

If “- -” is displayed as the Deviation value, it means that linearization has not been successfully completed yet.

Check the compass heading data

As part of the autopilot system commissioning process, it is recommended that you check the compass heading value displayed, against a good known heading source on various headings. Do NOT rely on the reported heading until compass linearization and alignment is complete.

Note

Once the linearization process has completed, it is possible that the heading value may have a slight offset of 2 to 3 degrees. This is common where installation space is limited, and the EV unit cannot be properly aligned to the vessel's longitudinal axis. In this case, it is possible to manually adjust the Compass Offset value.

System monitoring and adaptation

System monitoring and adaptationTo ensure optimum performance, after the initial linearization process is complete, the EV continues to monitor and adapt the compass linearization to suit current conditions.

If the conditions for linearization are less than ideal, the automatic linearization process temporarily pauses until conditions improve again. The following conditions can cause the linearization process to temporarily pause:

  • Boat speed < 3 knots.

  • Boat speed > 15 knots.

  • Rate-of-turn is too slow.

  • Significant magnetic interference is present.