Airmar GH2183 GPS Compass

This €650,- GPS compass is supposed to deliver a pretty good heading signal.

It reads in the brochure, 'Dynamic Compass Accuracy: 2° RMS (Best-in-Class)'. Clearly not suitable for commercial vessels, but fine for your chart plotter. Or so you would think. But in the video below you can see it's poor performance with only minor pitching. Not even rolling. This video was taken on a Dutch inland waterway. The waves were created by other vessels. We found that heavier pitching motions at sea result in a 22 degrees deviation either way. Inducing a heading signal that fluctuates a whopping 44 degrees. Nowhere near 2° heading accuracy in dynamic conditions.

The video below shows the weird change in heading signal when the boat pitches a little. I'll add a video a sea later.

Only after reading the manual (not the brochure) you will find that the sensor can best be placed on non-steel yachts. It is also best installed as low as possible in the boat and in the middle. That sounds to me like an open boat. Not a boat which is using an electronic chart plotter. The thing is, the GH2183 has no repeater. It's signals go right in to the computer / navigational software. So who would one use such a device in a very little boat, where you probably won't have a plotter?

Any way, to me it seemed like some of the advanced motion detectors were mounted on its side or something else went terribly wrong. So I send an email to the company I bought the sensor from.

This is the email I send to ‘’.

Dear sir / madam,

I own a HG2183 GPS + Heading sensor.

The GPS information seems very accurate with a high update frequency perfect for use on the electronic chart system / Nobeltec software.

But the magnetic heading is always off by a few degrees. It is actually never ever the same as the GPS heading. Sometimes it is more of than other times depending on the heading. This is of course caused by the ships deviation. But calibration doesn't seem to help, or change a thing. I also tried turning the sensor a bit to at least get the magnetic heading the same as the GPS heading in one heading, with zero wind and zero tide difference. But this never worked.

I understand that the magnetic heading system will never be perfect. So I won't complain to much about a system which has it's obvious cons. But the worst is yet to come. When the boat is pitching (not even rolling) the magnetic heading shifts at least 44 degrees in total. Let’s say from 22 degrees port to 22 degrees starboard.

This makes it useless for any radar plotter system. It is so far off that I wonder if the unit could be malfunctioning. It is certainly not near 2 degrees in a dynamic situation but al least 20 times as bad. It is so bad that it is impossible to steer by in a situation when heading is more important than true coarse, like crossing a shipping lane.

So I read the manual again and found out that the sensor is best installed at the center of the boat. Not many ships can do this. Or at least not with a GPS / Magnetic header sensor combination.

Did I choose the wrong sensor for my yacht? Or will it never work on a steel ship? Or could the sensor be defective? At this point I don't know what to do. For the sensor does not nearly perform as to be expected reading the product info in the brochure.

The sensor is installed on a steel ship, on the roof of the wheel house. Some 20 cm above the steel plating. I attached a picture of the boat so you can see what I mean.

I hope you can help.

Kind regards,

Rien van den Bergh

Up till now the people at Airmar have never replied to my email. Clearly I need some help to get this to work of the sensor is well off. But I almost can’t imagine Airmar selling a useless sensor for €650 euro. I will send the email again and let you know how it went.

Up till now I can’t say I’d recommend you to buy this sensor. I suggest you ask the retailer some serious questions concerning installation guidelines and expected performance.

Below you will find the pictures I mentioned in the email to Airmar. There you will see where the GPS / Heading sensor combination is located on the vessel.

Below you will find part of the GH2183 spec's, which seem promissing. At the time I though it would be a good enough midway system. Not to cheap but also not so expensive as a GPS Compass. Those will set you back €2700 to €3600.

GH2183 GPS Compas Specifications:

  • Static Compass Accuracy: 1° RMS when level

  • Dynamic Compass Accuracy: 2° RMS (Best-in-Class)

  • Heading Display Resolution: 0.1°

  • Settling Time: 1 second (adjustable)

  • Heading Data Output Update Rate

  • —10 Hz—NMEA 0183

  • —Adjustable up to 20 Hz—NMEA 2000®

  • Heading Variation: Yes

  • Rate-of-Turn Range: 0° to 70° per second

  • Rate-of-Turn Accuracy: 1° per second

  • Rate-of-Turn Data Output Update Rate:

  • —2 Hz—NMEA 0183 (Adjustable up to 10 Hz)

  • —Adjustable up to 20 Hz—NMEA 2000®

  • Pitch and Roll Range: ±50°

  • Static Pitch and Roll Accuracy: <1°

  • Dynamic Pitch and Roll Accuracy: <3°

  • Pitch and Roll Display Resolution: 0.1°

  • Pitch and Roll Boat Alignment: Yes (with software)

  • Pitch and Roll Data Output Update Rate:

  • —2 Hz—NMEA 0183 (Adjustable up to 10 Hz)

  • —Adjustable up to 20 Hz—NMEA 2000®

  • Supply Voltage: 9 VDC to 40 VDC

  • Supply Current: <120 mA

  • Power 1,100 mW

  • GPS Satellite Tracked: 14-channel (maximum)

  • GPS Satellites Acquired: 51

  • WAAS/EGNOS Satellites Tracked: Any Available

  • GPS Position Accuracy: 3 m (10’) with WAAS (95% of the time, SA off)

  • GPS-Fix Update Rate: 10 x per second (10 Hz)

  • Cold Start Acquisition: 60 seconds

  • Warm Start Acquisition: 37 seconds

  • NMEA 2000® Load Equivalency Number (LEN): 2

  • Certifications and Standards: CE, IPX6, RoHS, IEC60945

Follow the link below to check out the brouchure.

Follow the link below to check out the manual.