Raymarine Deviation Advice (fluxgate)

[RWS]

I just replaced the fluxgate compass (third one in 8 years) on my 2006 A.D. ST 6001 C Series Smart Pilot multifunction radar/autopilot/star wars gizmo.

I choose a better mounting location this time, resulting in a deviation of ONE DEGREE.

After the setup Iran N, S, E, & W at three different speeds, noting the autopilot setting vs. GPS COG vs. magnetic compass setting.

Base don the numbers below should I add (or subtract) a couple of degrees or just leave well enough alone?

Thank you,

RWS

 

[Capt. Bill1]

What the heck is going on at 15 knots!?

 

[Radioactive]

First off, for this purpose, disregard COG. It is only valid if there is zero current and/or wind. It is common for the vessel to have a heading different from COG.

When I had my Raymarine heading sensor ( the "fancy" upgrade, in fact ) it was usually rather correct. but note that you could run the correction routine simply by making a slow speed 360 degree turn ( timed to take two minutes, if memory serves me ). It was however usually quite accurate ( of course, in my neighborhood, there is very little difference between "true" and "magnetic" ).

The other consideration is that you are comparing one magnetic sensor to another. BOTH are susceptible to error. Some of the difference oi your chart may be comparing a "max Eastward error" to a "Max Westward error".

Similar to an old quote: "A man with two clocks never knows what time it is".

Always check each unit ( sensor, mag compass ) separately, against True bearings, measured visually. It is likely that each unit will have a different correction table, but both should be rather close. ( that is, better than your typical helmsman, +/- 2 degrees )

Note: Speed through water and SOG should have no, repeat, ZERO, effect upon these instruments. If you are having errors that vary with velocity, then you have other issues, such as nearby magnetic fields ( ie: wires with current flowing ) that are affecting the device reading.

 

[RWS]

quote:

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Originally posted by Capt. Bill1

What the heck is going on at 15 knots!?

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Wow, THANK YOU, GOOD CATCH !

That was a typo which I just fixed.

RWS