True or Magnetic North?

truebrit

truebrit

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When referring to charts using gps,should the unit be set to read true or magnetic north, surely when a gps collects co-ordinates they are lat /long and thats that.When giving a third party (coastguard) your postion giving bearings should they be magnetic or true. well folks your knowledgable advice would be greatly appreciated.

<hr width=100% size=1>Mike....... V8s are sweet music
 
I work in true on charts, GPS and anything else, using GPS bearings, I set ti to read true, I only ever convert to magnetic iof I use the nagnetic compass, I find it easier, alot of the time I am steering with the gps heading. Not ness the right way to do things, but thats what I do. IMHO

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If you really mean a bearing eg from a conspic. obj. on land, a structure at sea or some-such then presumably you will have taken this using your handbearing compass and thus it's magnetic. No handbearing compass and you've used some other means then you might need to warn the third-party of the approximation depending how far out you reckon it could be.

Overall, its not much of an issue either way given the likely (in)accuracy of your bearing and the probable distance off.

ps like Colin I have my GPS set to true and work in true on the chart. Yeoman user see!

<hr width=100% size=1><font color=blue>A convert to steel boats and displacement cruising - the only way to go</font color=blue>
 
If giving say coastguard position, from GPS, would give them lat and long. Can't see many issues for whether GPS should be true or magnetic. If giving bearings, you should simply say if they are magnetic or true to avoid confusion. Most bearings given would be magnetic as taken from compass. Why give coastguard bearings when you can give them accurate GPS lat and long if you have a working GPS on board?


<hr width=100% size=1>There is no such thing as "fun for the whole family."
 
The manual of my autopilot recommends to set GPS bearing to magnetic.
That makes it consistent with the electronic compass, and this should avoid continuous corrections from the pilot, which receives both the gps and the compass signals.
In practice, I tried both settings, and never saw noticeable differences.
Then I decided to keep the GPS on true north.

Fully agree with Brendan - all the above does not affect the position anyhow.

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Bearing should be either magnetic or true and state which it is, if given as a position indicator. But not compass. And from a charted object helps too.


If using a GPS position make sure it is where you are and not the cross hairs on a chart plotter, Heard of a mayday sent that put there position middle of IOW and they where a commercial fishing boat [due to cross hairs in wrong place] Coast guard did a direction find and got them ok though.


<hr width=100% size=1>Julie ,
IMOSHO of course,/forums/images/icons/smile.gif
 
For what it's worth I have the GPS set at Magnetic so that it "agrees" with the compass. Mind you we always steer using the GPS so I don't think it matters. If I then have to consult chart I have to remember variation which is all good practice for when GPS packs up. Embarrassed to say that I've never noticed much deviation - well of the magnetic sort anyway - so I forget about it. As an aside, I've yet to find a charter yacht with a deviation table on board. Agree that if giving bearings to 3rd party then we would say what format they were in.

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All bearings on a chart are in degrees True, therefore if you are using a GPS, these should also be in True, otherwise confusion will reign. Your GPS should also be using the appropriate datum eg WGS 84, corresponding with the chart used.
Any adjustment for variation or deviation, is made when steering using your compass.
Hand compass bearings are normally only adjusted for variation, either when taking a fix, or reporting a position/bearing to HMG.
Don't forget, your compass can get deviation from most metal or electrical/electronic sources - this includes specs, beer cans, mobiles & some flares (metallic chemicals).

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Only thought about giving bearings from conspicuous objects etc,in the event of Gps on the blink (batteries flat,full of sea water etc!!)

<hr width=100% size=1>Mike....... V8s are sweet music
 
Than give them in magnetic, as read off the hand bearing compass, because if you are in trouble you have enough stress and diont want to start adding and subtracting variation!

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