gps heading

[Guest]

Ok so I have just finished installing a full set of raymarine instruments.

These are networked via backbone seatalk ng.

 

i am getting a wide variation on heading/ track on my different instruments.

 

Eg, My compass shows 80deg my i70 control pilot says 83deg,

My raymarine chartplotter a50d shows 122deg. Now these should all share the same data.

 

The pilot control head can be adjusted.

the a50d has an internal gps.

 

So then on my garmin plotter which is seperate with external gps it shows 111degrees.

 

Any ideas how to get these to be the same?

 

Yes they are all set for magnetic compass heading.

 

Kinda average to give someone a heading to sail and they have 3 options over 50 degrees difference.

 

Thanks skins

[Absolution 7]

Hey Skinner... Your GPS heading won't make any sense until you are moving because it doesn't have a compass. If you're moored then it could report anything. Go for a motor and you'll probably find you're sweet.

[idlerboat 116]

Definately as above.

But In this day and age I would change eveything to true north.

Then makes sure you have done the full on water programing of your fluxgate compass.

Then correct it at the head unit to true.

It will always be a couple of degrees out to the gps based inputs.

 

This means that the only time you have to take into account deviation/ variation is if you are reffering back to a static compass. (say using a hand bearing compass, or the "boats compass").

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You set the chart plotter to North Up. ( like a paper chart) but dont have to use the mag north rose and deviation stats.

 

I always suggest that on a radar ONLY page that you set this up with heading UP. This makes it much easier to work out where other vessels are, but the radar overlay on the chartplotter (north up) still serves its purpose.

 

A normal magnetic compass will always be far less accurate than the fluxgate becuase you have to do a manual "compass adjustment" to get it close. It may also be prone to inacuracys and changes if the boat sits for an extended pieriod of time in the one spot and as you go through areas of local anomilies. (It is still good practice to "retune" your fluxgate compass from time to time)

 

As a final point, the fluxgate compass only drives your auto pilot when you are running to a compass bearing only. In this setting it makes no allowence for leeway..

When you are running to a lat lon (way point) the gps provides the data for heading and other features such as cross track error and adjustment.

In this mode you should see two lines. One is the boats orientation (the direction that the boat is pointing provided by the fluxgate compass) and the other, the direction the boat is acctualy traveling, provided by the gps data.

 

(You probaly know all this, but I just thought I would put the whole lot down for others who are setting up for the first time)

 

cheers.