Autopilot Calibration

[Flying Knight]

My Raymarine autopilot won't let me calibrate for some reason. When going through the steps detailed in the manual the display says "Cal Lock". The only thing the manual has to say about this is its usually used in charter boats to keep people from screwing things up. Beyond that it doesn't state how to disengage, which I need to in order to recalibrate. Anyone know how to fix this?

[DotDun]

You don't mention the model of the AP.

IIRC, the cal lock can be released in the dealer setup.

[Cephious1]

I found the entire manual on line, when I searched google for my st4000. I recall that the units can be locked to prevent anyone from changing the calibration settings..if you forgot the code the news is not good the unit locks can only be redone by the manufacturer . You might want to check the raytheon web site for more info.


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[Ex-Calif]

Guessing you read that in the ST4000 manual.

In Standby mode you need to press and hold standby button for 14 seconds to enter "dealer" mode.

ST5000 same drill

[Flying Knight]

Originally Posted by Ex-Calif

Guessing you read that in the ST4000 manual.

In Standby mode you need to press and hold standby button for 14 seconds to enter "dealer" mode.

ST5000 same drill

I have the st4000+ and can confirm this works. I checked it yesterday and if I remember correctly doing this first activates an initial set of parameters that I could configure, but holding the standby button longer brought me to a second set that were the dealer options. At least I think that was my confusion. Seems like I had to hold it longer than 14 seconds. The instruction should read "Hold standby until the display reads 'Cal?'".

[Ex-Calif]

I find the Raymarine button pressing instructions confusing as well.

Particularly the internal fluxgate cal on the tillerpilot models...

I did turn after turn not realizing I was not in the right mode...

[djmarchand]

I know that this sounds heretical but why do you want to calibrate your autopilot? To get it to read the same as your magnetic compass, right? But why bother.

On my first boat with an autopilot I went through the laborious process of first swinging the magnetic compass, adjusting it and if necessary (it wasn't) making up a correction card. Then calibrating the autopilot to it.

But by the third boat, I just checked on a couple of courses how the autopilot tracked the magnetic compass and how the magnetic compass tracked a known course. It was always within 3-4 degrees.

If you are going to be dead reckoning over a couple of hundred miles offshore, then maybe it matters. But not for coastal navigation with a chartplotter.

David

[colemj]

In addition to calibrating the coordinates of the compass itself, the autopilot calibration procedure also compensates for magnetic interferences. In addition, most calibrating routines include calibrating the rate of turn, the response parameters, rudder gain and rudder/counter-rudder settings. These make a huge difference in performance.

Mark

[Flying Knight]

No, the autopilot was never calibrated after installation on the boat and deviates significantly from the actual heading it displays.

[DotDun]

Originally Posted by djmarchand

I know that this sounds heretical but why do you want to calibrate your autopilot? To get it to read the same as your magnetic compass, right? But why bother.

On my first boat with an autopilot I went through the laborious process of first swinging the magnetic compass, adjusting it and if necessary (it wasn't) making up a correction card. Then calibrating the autopilot to it.

But by the third boat, I just checked on a couple of courses how the autopilot tracked the magnetic compass and how the magnetic compass tracked a known course. It was always within 3-4 degrees.

If you are going to be dead reckoning over a couple of hundred miles offshore, then maybe it matters. But not for coastal navigation with a chartplotter.

David

Modern APs calibrate their compass to COG from the GPS +/- mag. variation. It's as simple as a few button pushes and steering the boat in a straight line for ~30 seconds.

[colemj]

Originally Posted by DotDun

Modern APs calibrate their compass to COG from the GPS +/- mag. variation. It's as simple as a few button pushes and steering the boat in a straight line for ~30 seconds.

That isn't how our AP compass is calibrated. Ours require a 360* circle done at a specific rate of turn and doesn't involve the GPS at all. The rest of the AP calibration is done by doing S-turns at various rates of turn - the AP does this itself and it involves a nominal straight line for 2-3 minutes.

Mark

[goboatingnow]

The circular process is to linearise the fluxgate compases and build a deviation table.

dave

[colemj]

Originally Posted by goboatingnow

The circular process is to linearise the fluxgate compases and build a deviation table.

dave

Yes, isn't that calibrating the compass?

Mark

[goboatingnow]

Originally Posted by colemj

Yes, isn't that calibrating the compass?
Mark

calibration is more correctly comparing it to a known reference, the primary purpose of the 360 thing is to build a deviation table. modern fluxgate compass are self calibrating in that they are shipped with a known positional accuracy, before been installed.

dave

[DotDun]

Originally Posted by colemj

That isn't how our AP compass is calibrated. Ours require a 360* circle done at a specific rate of turn and doesn't involve the GPS at all. The rest of the AP calibration is done by doing S-turns at various rates of turn - the AP does this itself and it involves a nominal straight line for 2-3 minutes.

Mark

What goboatingnow said.

What I was replying to was the process djmarchand explained as a laborious task of aligning the AP with the magnetic compass.