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Discussion Starter · #1 ·
On the 38 I just bought it has the raymarine package (2003 so is that the rl -80?) Anyways I noticed the course to the island is different than my other gps units. So in the set ups I see that instead of magnetic north with the automatic offset (is that 17 degrees?) someone manually changed it to 1. Thus when I set a course on the auto pilot based on the chart plotter it gets me there but the course reading on the auto pilot and the gps both is 16 or so degrees off from what it should say. I am guessing that this is the GPS compus set up (or the auto pilot setup?), but what was interesting is that the GPS and the autopilot both displays the wrong degree course heading (but the units get me there and back just fine, they both simply display the wrong course. I would have thought the GPS would know the direction you are heading since it is a GPS. Anyway I am guessing that I need to set the "auto pilot compus ???" or something to fix this? Every GPS I have had knows where it is going , so this is all new to me. Its intersting here the GPS is showing the wrong course that I am assuming it is getting from the auto pilot, but I am not really sure what is going on here, anyone know?

This post edited by Wolfpack 06/10/2008
 

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What model AP? I assume that you set the heading to display the correct magnetic course? Also check to make sure the map datum your using is WGS84 (IIRC - it is early and I have no caffene in my system yet :) ). The heading display you are looking at may be the AP compass or the GPS heading. The GPS does not know which way the boat is pointing it only knows the track where the boat has been and that is where the heading it displays comes from. That means that the heading it displays is delayed. The straighter the course you have been on and the faster the GPS updates its position the closer the GPS heading will be to the real world heading. Somewhere in the AP setup there is an adjustment to tweak the heading that is displayed from the AP compass. I don't recall for the RL80 offhand but it is in the AP manual. The GPS heading and the AP compass heading are usually never perfectly in sync. On top of that they both of those headings are also rarely in sync with the magnetic compass heading. Magnetic compass adjustment is another thread but depending on the compass, the install, where you are (due to local magnetic variance) and how long it has been since the compass has been compansated it may well be off more than a few degrees.
 

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If it's an S1G unit I would send it back to Raymarine. My Ap was a 2004 model and it was dangerously defective. After about a year of use it would not hold a course. At times it would make a hard turn without warning.

It turns out several of the caps were wired to the pc board backwards. As they failed my unit became worse and worse.

This problem was wide spread. Raymarine repaired it without charge.

Raymarine should have issued a recall for this model unit.
 

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Discussion Starter · #4 ·
well when the boat is on auto pilot it is heading straight, and even at 20 knots , the gps and the auto pilot both show a course that is 16 degrees off what is really happening. The prior owner set the offset 16 degrees off, thus the outcome is the gps and autopilot get the boat to the proper place, but show the wrong course. In the gps setting I changed the offset to automatic (I think that is 17 degrees for this part of the world). So what now happens is the compus course is correct, BUT when you are in the gps mode where it shows the boat as a triangle in the center of the screen and the lines scroll down as you head toward your weighpoint, the center triangle that represents the boat is not pointed straight, and pitched at a 17 degree angle as if the boat is heading off course, but the triangle moves straight up the screen (it does not track off course). Thus its almost like I have to set up the AP compus (you might know the proceedure of turning the boat in a slow circle over a 2 minute period of time). But the wierd thing is why does the GPS show the triangle poitched at an angle? I would have thought the GPS would know the correct course from satalite data, but its almost as if the GPS is displaying the course data from autopilot. So no with the corredct offset, the compus course displayed by the auto pilot and gps are correct, its just the gps thinks the boat is moving off course (not off the stright line, butt eh triangle represneting the boat on the GPS is pitched at an angle), I might not have an AP compus, I was reading and I think this is an option, so if it is an option and I do not have it, then maybe the autopilot is getting its data from the GPS, so if this is the case.... I better stop here, cause I am confused, I need to go read the manual cause I remember it talking about setting up the AP by making a 2 minute slow circle, and an external AP compus being a "option."

This post edited by Wolfpack 06/11/2008
 

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What model AP??? Odds are good that you have an AP compass. The option you thinking of is likely an upgraded compass. If the only issue is the boat marker not displayed correctly (the GPS is set to course up correct?) then maybe a system reset of the GPS is in order. Note that you will likely lose your waypoints so back them up before you do that.
 

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Discussion Starter · #7 ·
ok I got it, I pulled out the 5 books that came with the unit and read them last night, then took the boat out for sea trial, it seems I needed to reset the compus for the auto pilot. I did circles in the boat while the AP calculated deviation (it determined 1 degree deviation) , then I plotted a straight course and the autopilot communicated with the gps to determine what the compus heading should really be.

so now the AP, and the GPS are right on.

It seems the GPS course over ground is computed by GPS and its satalites, but the gps "heading" data is simply downloaded from the AP compus, thus when the AP compus was off, the gps heading was off (I did not notice that COG was right on.)

Anyway all fixed, thanks everyone for the input.
 
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