Magnetic vs True North for Electronic Nav Instrument Setting

[hardee]

This is getting really good. At first I was thinking Greg had switched the terms. It makes sense that with Magnetic as the primary setting, declination only changes the orientation of the charts. Then what Boris says about True makes some sense too.

I have the feeling it is going to come down to what the electronics guys at Rogers Marina decide, because it sounds like it will be dependent on what the participants on the electronic community on SleepyC can do to get along.

This is a really interesting thread. Thanks to all for all the enlightening comments. I am learning a lot.

Harvey
SleepyC

[hardee]

Sorry Duplicate Post -- again.

Harvey
SleepyC

[hardee]

So after going over this thread several times, and talking with several knowledgeable folks in my area, I am considering strongly that setting everything to magnetic may be the best move. (At least for the electronics) and I can tilt the paper when I need to to get the same picture. Truth is that the electronics are all showing course up or heading up anyway. (There is another one for consideration.) Does either course or heading have any advantage over the other. I don't often run a course, so generally use "heading up" for the MFD and now it is available on the AIS as well so both of those screens look the same.

Another twist.

Harvey
SleepyC

[NewMoon]

I like magnetic, and course up - the chart image doesn't keep shifting around as much as with heading up.

If I'm not following a course, my chartplotter defaults to heading up (track up, actually - based the direction I have been going, not where the boat is actually pointing). Don't have an electronic compass feeding heading to the chartplotter, or an autopilot holding me on course. Maybe I would choose differently if I did.

My Radar (stand-alone, not integrated on the chartplotter) displays heading up, in keeping with the idea that Radar shows what is - what I might be able to see if I looked straight ahead. Seems to make sense to me, or maybe I'm just used to it that way.

[thataway]

The reason to use "heading up" is that the radar will overlay accurately--with the new chart plotters at 10 HZ this should be accurate. The heading up is the direction the boat is traveling at that instant (10x minute sampling time, and of course will vary).

"Course up" is toward a waypoint--this may or may not be what your current heading is. If you have not set a way point, the GPS will probably revert to "heading up".

Because "course up" or North up, is a stable geographic point, the chart plotter should not move unless you are way off course (cross track error), and then only very slowly.

I use heading up. I want to see what is on the chart, and compare that to what I am visually seeing.

Generally when planing with a paper chart, it is easier for me to use North up orientation--since the Lat and Long lines are square to the chart's North up, and it is then easy to lay a course, and measure the angle with a protractor, without having to go to the rose, and step off with parallel rules.

Yes, there are times when it is nice rotate the paper chart to your course, so you can see what the visual picture will be. The chart plotter makes all of this un-necessary. However sometimes it is still very valuable to look at the paper chart the evening before a day's run, to look for alternate routes, coves, and hazards which you might not notice when looking at the chart plotter or computer.

The new Garmin xs series (1040xs for example) has WiFi built in, so you can interface it with the Garmin Blue Chart mobile, and transfer waypoints and routes directly from the i pad, or a computer. When planing on the i pad, I use N up. I don't know if you can do magnetic courses and then transfer to the MFD--but you can change to magnetic courses on the MFD, after the route is placed on the MFD. If your i pad does not have a built in GPS, the i pad can get position data from the Garmin MFD via WiFi.

[journey on]

I keep repeating this, just to make sure that it's clear that True/Magnetic compass reference is different from heading-up or course-up. Your direction will show differently depending on if you're in True or Magnetic. About 14 deg different in SoCal, different elsewhere.

True is geographic North and of course, Magnetic is magnetic North. The difference between Magnetic varies around the world, but True stays true.

Both represent only reference frames in geographic maps, electronic or paper. They're related, but not the same.

Heading-up or Course-up show you a direction within the True/Magnetic reference you've chosen. That is you can have heading-up shown in True or Magnetic, and the chart will rotate to accommodate the direction in the reference you've chosen. And Bob has given an excellent discourse on the advantages or either.

Please don't confuse the direction (Heading/Course) with the reference (True/Magnetic.). Do set the reference in all your instruments to one reference, either True or Magnetic.

Boris

PS: thank God for spell check.

[hardee]

Boris and Dr Bob, Thanks for the excellent posts here. This is been a very helpful discussion. I really appreciate all you time and effort spent here, (and not just on this topic but on all of them). My preference has always been to heading up on the MFD, but I have vacillated on the Northerly reference. I am working now on deciding, and will switch everything to one point soon. The quarter is still in the air. Thanks for keeping it spinning

Harvey
SleepyC