Gyro vs GPS Compass for Autopilot Heading

What is a gyrocompass

A gyrocompass is a heading sensor that uses the principle of a spinning mass or solid-state gyroscopes to sense rotation and maintain a reference direction. In marine autopilots, gyro-based sensors are often integrated into the course computer or as a separate heading sensor, providing continuous heading data even when the boat is stationary or moving slowly.

Gyrocompasses do not rely on the Earth's magnetic field, so they are not affected by magnetic variation or onboard magnetic interference. They provide a stable heading reference that responds quickly to changes in course, which is valuable for autopilot control. For example, Raymarine Evolution autopilot packs use a 3D heading sensor that combines gyro and accelerometer data.

• Gyro sensors measure angular rate and integrate to determine heading.
• They are not affected by magnetic deviation from onboard equipment.
• Gyro-based heading sensors are common in modern autopilot systems.

What is a GPS compass

A GPS compass uses signals from satellites to determine the boat's heading by comparing the positions of two or more antennas. It provides an absolute heading reference that is independent of magnetic fields, making it useful for vessels with significant magnetic interference or for precise navigation.

GPS compasses require a clear view of the sky to maintain satellite lock, and they may have slower update rates compared to gyro sensors. They are often used as an additional heading source or for redundancy in autopilot systems, as seen in some marine autopilot reviews.

• GPS compasses use satellite signals to calculate heading from antenna positions.
• They are not affected by magnetic variation or onboard magnetic fields.
• They need a clear view of the sky and may have slower response times.

How autopilots use heading sources

Autopilots rely on a heading sensor to know the boat's current course and to make corrections. The heading sensor provides data to the course computer, which then commands the drive unit to adjust the steering. The quality and type of heading source can affect how smoothly and accurately the autopilot maintains course.

Many modern autopilot systems, such as Raymarine's Evolution series, use a 3D heading sensor that combines gyro and accelerometer data. This sensor is part of the autopilot system and is designed to provide stable heading information even in rough conditions. For a deeper look at heading sensor options, see our marine autopilot reviews.

Some autopilots can also accept heading data from external sources, such as a GPS compass or a separate gyrocompass, via NMEA 2000 or other networks. This allows boat owners to use an existing heading sensor or add redundancy. The EV-200 Power Pilot is one example of a system that integrates with external heading inputs.

• The heading sensor is a critical component of the autopilot system.
• Integrated sensors, like Raymarine's 3D heading sensor, combine gyro and accelerometer data.
• External heading sources can be connected via NMEA 2000 for flexibility.

Comparing gyro and GPS compasses

When comparing gyro and GPS compasses for autopilot heading, consider the boat's typical operating environment. Gyro-based sensors are generally more responsive and do not depend on satellite reception, making them suitable for all conditions, including near bridges or in harbors where satellite signals may be blocked.

GPS compasses provide an absolute heading that is not subject to magnetic variation, which can be beneficial for long-distance navigation or in areas with high magnetic interference. However, they require a clear view of the sky and may have a slower update rate, which could affect autopilot performance in dynamic conditions.

For most recreational boats, a gyro-based heading sensor integrated into the autopilot system is sufficient. If you already have a GPS compass on board, you may be able to use it as an additional heading source, but it is not a replacement for a dedicated gyro sensor. When comparing autopilot options, marine autopilot reviews can help you see what each system offers.

• Gyro sensors are more responsive and work in all conditions.
• GPS compasses offer absolute heading but need clear sky view.
• Integrated gyro sensors are standard in many autopilot packs.

What to pick for your situation

The choice between a gyro and GPS compass depends on your boat's existing equipment and your needs. If you are buying a complete autopilot pack, it likely includes a gyro-based heading sensor, so you do not need to worry about a separate GPS compass unless you want redundancy.

If you are building a custom system or upgrading an existing autopilot, consider whether you already have a GPS compass that can be integrated. Check the autopilot's compatibility with external heading sources via NMEA 2000. For a full list of options, see our complete autopilot packs guide.

For most boat owners, a gyro-based heading sensor is the practical choice because it is integrated, reliable, and does not depend on satellite signals. A GPS compass can be a useful addition for redundancy or for vessels with specific navigation needs. Explore core packs if you plan to keep an existing drive.

• Complete autopilot packs usually include a gyro-based heading sensor.
• Existing GPS compasses can be integrated if compatible.
• Gyro sensors are the standard for most recreational boats.

Frequently asked questions

Here are answers to common questions boat owners ask about gyro and GPS compasses for autopilot heading. These explanations focus on how the technologies work and how they fit into an autopilot system.

What to pick for your situation

Questions

Can a GPS compass replace a gyro compass for autopilot?

A GPS compass can provide heading data, but it is not a direct replacement for a gyro-based sensor because it requires clear sky view and may have slower updates. Many autopilots use gyro sensors as the primary heading source and can use GPS as a secondary input.

Do all autopilot packs include a gyro sensor?

Most complete autopilot packs include a heading sensor that uses gyro technology, such as Raymarine's 3D heading sensor. Core packs may not include a sensor, so you would need to purchase one separately.

Is a GPS compass more accurate than a gyro compass?

Accuracy depends on the specific models and conditions. GPS compasses provide absolute heading without magnetic variation, but gyro sensors are generally more responsive. Both can be accurate, but they serve different purposes.

Can I use my existing GPS compass with a new autopilot?

If your GPS compass is NMEA 2000 compatible and the autopilot supports external heading sources, you may be able to integrate it. Check the autopilot's specifications and the manufacturer's documentation.