joeh
Well-Known Member
hello forum
question : which should i set my hh gps to ? default is magnetic. i use paper charts only. thks
question : which should i set my hh gps to ? default is magnetic. i use paper charts only. thks
true or magnetic
- Thread starter joeh
- Start date
alec
Well-Known Member
I find True works for me but I expect we all have our own preferences.
Took me quite a while to convert but am now a true believer.
Took me quite a while to convert but am now a true believer.
Blue5
Well-Known Member
My HH set to true, same as the charts
michael_w
Well-Known Member
Magnetic for me. Saves on the sums.
rosssavage
Well-Known Member
Magnetic. Then if GPS fails suddenly, I can instantly revert to steering same heading by compass without having to add correction under a possibly high workload.
S
Skyva_2
Guest
Have always used True.
MoodySabre
Well-Known Member
True. The correction to magnetic is so small round here that it is within a reasonable "hand steering tolerance". For coastal hopping who looks at the compass anyway /forums/images/graemlins/shocked.gif
wotayottie
Well-Known Member
[ QUOTE ]
Magnetic. Then if GPS fails suddenly, I can instantly revert to steering same heading by compass without having to add correction under a possibly high workload.
[/ QUOTE ]
Got to say your reply really surprised me. Could understand it from some single handed traditionalist in an old sailing boat (probably carries a lead line too!) but in a mobo .........
When did your GPS last fail? And do you carry only one? For that matter, where does the high workload come from on a Mobo? And do you actually steer the boat by hand outside congested areas where you might have to dodge anyway?
I guess its sense still to have a compass as a back up but personally I have never had to steer by one in tens of thousands of sailing miles. Cant remember tha last time I had the cover off it.
Magnetic. Then if GPS fails suddenly, I can instantly revert to steering same heading by compass without having to add correction under a possibly high workload.
[/ QUOTE ]
Got to say your reply really surprised me. Could understand it from some single handed traditionalist in an old sailing boat (probably carries a lead line too!) but in a mobo .........
When did your GPS last fail? And do you carry only one? For that matter, where does the high workload come from on a Mobo? And do you actually steer the boat by hand outside congested areas where you might have to dodge anyway?
I guess its sense still to have a compass as a back up but personally I have never had to steer by one in tens of thousands of sailing miles. Cant remember tha last time I had the cover off it.
dukes4monny
Well-Known Member
Magnetic for me. My reasoning is: because I'm plotting with paper charts and taking bearings with a handheld compass and also my handheld GPS, I know that whichever I use, I have to adjust to True when plotting to the chart....
Simes
Well-Known Member
The answer has to be True. If you use magnetic then you have a calculation to make in both directions, you need to apply Variation to get to True or Deviation to get to Compass. At least in True you can use the data supplied direct to the chart.
Simes
Simes
savageseadog
Well-Known Member
Magnetic has to be the amateur approach. True is true, to which any corrections and variations can be applied.
Danny
Well-Known Member
Think I'll invent a binnacle compass with a movable lubber line linked to a servo mechanism fed via NMEA from the GPS so that the appropriate amount of variation for the boat's position is automatically applied so that it reads True instead of Magnetic.
/forums/images/graemlins/laugh.gif
/forums/images/graemlins/laugh.gif
lw395
Well-Known Member
So long as you know which you are using, do what's most useful to you.
If you want to take the bearing to waypoint straight to a steering compass, then mag is useful.
If you want to plot your course on the chart, then true is useful. Personally, I rarely plot my course on the chart, just my position.
Mostly I'm interested in the difference between a Bearing and a Course, and how they are both changing over time. So long as they are both true or both mag, I don't much care which, so long as I know. When sailing I mostly want to know whether I'm laying the next headland or whatever. The difference between course and bearing tells me this.
The compass is mostly used to tell me if the wind is backing or veering, when beating. When you don't have sails, stars or a horizon to steer to, then it gets used for short term course checking, as actually steering to a GPS can tend to make thew boat weave about.
There are many ways of using these instruments, its not really about right and wrong, more about being methodical and self-consistent.
Of course if you are in a watch system you need to check with other people and be prepared to understand other people's methods.
If you want to take the bearing to waypoint straight to a steering compass, then mag is useful.
If you want to plot your course on the chart, then true is useful. Personally, I rarely plot my course on the chart, just my position.
Mostly I'm interested in the difference between a Bearing and a Course, and how they are both changing over time. So long as they are both true or both mag, I don't much care which, so long as I know. When sailing I mostly want to know whether I'm laying the next headland or whatever. The difference between course and bearing tells me this.
The compass is mostly used to tell me if the wind is backing or veering, when beating. When you don't have sails, stars or a horizon to steer to, then it gets used for short term course checking, as actually steering to a GPS can tend to make thew boat weave about.
There are many ways of using these instruments, its not really about right and wrong, more about being methodical and self-consistent.
Of course if you are in a watch system you need to check with other people and be prepared to understand other people's methods.
bluedragon
Well-Known Member
[ QUOTE ]
When did your GPS last fail?
[/ QUOTE ]
Twice in the past 2 years! But not the unit....the signal was I assume corrupted by military jamming the first time, and second time who knows. The result was the same, the GPS suddenly had us zig-zagging off course and at an impossible speed. First time lasted about 15 mins off N.Devon in poor viz.
The purists will always go for true. I've always used magnetic in the past but have wondered whether now using GPS/Chart plotters I should shift over to true? However, we still use a hand bearing compass and the tillerpilot reads magnetic...so again why create confusion.
There is no correct answer to this IMO. Do whatever you have done in the past and will minimise mistakes, whether that be using T or M doesn't matter so long as it's clear to everybody on board.
When did your GPS last fail?
[/ QUOTE ]
Twice in the past 2 years! But not the unit....the signal was I assume corrupted by military jamming the first time, and second time who knows. The result was the same, the GPS suddenly had us zig-zagging off course and at an impossible speed. First time lasted about 15 mins off N.Devon in poor viz.
The purists will always go for true. I've always used magnetic in the past but have wondered whether now using GPS/Chart plotters I should shift over to true? However, we still use a hand bearing compass and the tillerpilot reads magnetic...so again why create confusion.
There is no correct answer to this IMO. Do whatever you have done in the past and will minimise mistakes, whether that be using T or M doesn't matter so long as it's clear to everybody on board.
lw395
Well-Known Member
15 minutes loss of gps should not cause anyone too much problem. So long as you realise there's a problem. Its another good reason not to steer to the GPS though, much better to have been steering a compass course since the last 'good' position.
bluedragon
Well-Known Member
Hence the value of using magnetic on both...
lw395
Well-Known Member
Depends how you look at it. The course you are steering is probably neither your 'bearing to waypoint' or COG. You could equally say it makes it easier to plot your position relative to WP if its all in true. I think the issue of potential jamming etc is a reminder that we should still be logging our course steered, particularly in poor vis, so that we can fall back on some DR.
Main thing is to have the information. And to understand what the machines are telling us.
Perhaps we should think a little more often 'what will we do if the GPS packs up now?'
Also, how does the GPS know what the variation is? Will it agree with your chart?
Main thing is to have the information. And to understand what the machines are telling us.
Perhaps we should think a little more often 'what will we do if the GPS packs up now?'
Also, how does the GPS know what the variation is? Will it agree with your chart?
LadyInBed
Well-Known Member
I'm a MagMan.
I normally only transfer Lat and Long's to chart, the exception is COG.
When working out a CTS on the chart, that gets transferred to the compass so GPS is not involved.
So whichever you use, you will have to convert at some point, so for me it is best to know that everything that comes to or from the chart needs converting.
I normally only transfer Lat and Long's to chart, the exception is COG.
When working out a CTS on the chart, that gets transferred to the compass so GPS is not involved.
So whichever you use, you will have to convert at some point, so for me it is best to know that everything that comes to or from the chart needs converting.