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Old 05-03-2017, 06:12 PM   #21
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[QUOTE=Capt.Bill11;549929][QUOTE=Seevee;549890]
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Originally Posted by Capt.Bill11 View Post

To each his own.

But true is what you plot on a chart. So why would you want to convert?

Magnetic North can and does move. True doesn't.

There is no need for magnetic in this day and age.

https://books.google.com/books?id=qN...egrees&f=false
Bill,

Neither Magnetic North nor true north moves, a least enough to be an issue (perhaps 500 miles in a lifetime) True you have magnetic deviation and variation. But ALL of the charts produced for our products, plus ALL gps units use magnetic. When you plan a route, you do it in magnetic, and virtually all of the information you get from your chart plotter is magnetic. If you use true, you have to convert back to magnetic to get anywhere. Even the old charts with loran LOPs used magnetic.

The ONLY time you need true if you're operating above the magnetic north.. believe its something like 75d north, and that's an ugly hostile place to operate anyway. When I flew the route to Hong Kong we would convert to true up there for about 5 hours over the pole, and glad to get back to magnetic on the other side.

We "USED" to use true... many years ago. Perhaps back in the years of VLF and Omega. I've used them, but can't remember how they work other than they were a PITA. Not any more. Really what do you see in true that prompts you to use it, I don't understand. Please let me know.
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Old 05-03-2017, 07:16 PM   #22
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Again I ask you, if courses on charts should be plotted in true, why would you not use true and instead use magnetic, which you have first to convert to true to plot?

What's the point?

So 500 miles doesn't count as moving?

"The Earth's magnetic poles move. The magnetic North Pole moves in loops of up to 50 miles (80 km) per day. But its actual location, an average of all these loops, is also moving at around 25 miles a year [ref]. In the last 150 years, the pole has wandered a total of about 685 miles (1102 kilometers)."

What are you going to do when it flips?
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Old 05-03-2017, 08:31 PM   #23
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Again I ask you, if courses on charts should be plotted in true, why would you not use true and instead use magnetic, which you have first to convert to true to plot?

What's the point?

So 500 miles doesn't count as moving?

"The Earth's magnetic poles move. The magnetic North Pole moves in loops of up to 50 miles (80 km) per day. But its actual location, an average of all these loops, is also moving at around 25 miles a year [ref]. In the last 150 years, the pole has wandered a total of about 685 miles (1102 kilometers)."

What are you going to do when it flips?
All true, but what reference do you use for navigating? How do you get true north on your plotter? How do you know where true north is?

And a movement in 685 miles in 150 years might mean that you'll miss the dock by 3 inches.

I'm not convinced but sure have an open mind to a reasonable explanation.
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Old 05-03-2017, 08:43 PM   #24
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What are you going to do when it flips?
Rotate my compass 180 degrees.
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Old 05-04-2017, 05:39 AM   #25
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What are you going to do when it flips?

We will all figure out how to finally get to dry-land.

(Obscure movie reference of the day)
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Old 05-04-2017, 07:45 AM   #26
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I have just about every navigation app there is on my iPad's. I need them to let customers play with so they can decide what app they prefer to use as a secondary or tertiary navigation tool.

The hands down winner they choose most often, after using them, is Transas iSailor. A lot of people assume iSailor is a bit player but the parent company, Transas, has been a global leader in shipping navigation & bridge management systems for years. Transas is not a "bit player" at all.. With all the nav apps available on my iPad, the one I go to most is iSailor. It's also the one most of my customers choose when they get to use them all side by side.

Some still choose Navionics, and of course Garmin Blue Chart for Active Captain, but Blue Chart Mobile is not really a full featured nav app and is really intended as a planning app.

What I like with iSailor is the simple clean nature and the well drawn NOAA feel vector charts. No matter where I have gone, or done a delivery, the iSailor charts have been spot on and in many cases a more accurate rendering than Garmin or Navionics.

Also, in course up, everything displays perfectly, including text & soundings. Navionics, for example, will not rotate text, just the chart, a real PITA for when you may prefer to run a course up view. There really is no excuse for this with Navionics in this day and age.

In general I am not a fan of the Navionics chart renderings. Still trying to figure out where the little pink "Peeps" are shown in Chart #1.....

None of these apps are perfect in every aspect but for myself, and most of my customers, they prefer iSailor over the others.

Disclaimer: I would never suggest and I am not suggesting the use of an iPad as your primary (only) means of electronic navigation.
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Old 05-04-2017, 08:47 AM   #27
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We have Navionics, really nice application, generally use it while I'm in the salon with a cup of coffee in the morning planning out the next stop (out vacations are rather open ended). The application has a lot of information including marina details/restaurants etc. The other feature I like is tidal flow and tide times. One major feature it doesn't have which I would really would like is Active Captain, heard good things about Garmins app with AC.
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Old 05-04-2017, 10:49 AM   #28
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One app for iOS that I haven't seen mentioned here (maybe I missed it) is Navimatics. It is simple and basic and interfaces with the Active Captain database. The charting is vector and while it looks ok, it is not as sharp and almost raster like as is the iSailor charting.

I particularly like its easy way to click on a tide or current symbol and get a graphical chart of the data as well as point to point distance measuring.

I mostly use it as a look ahead supplement to our helm mounted chart plotter.

If iSailor had an easy way to measure a point to point distance and the tides and current lookups, I would use that one just for its pretty charting.

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Old 05-04-2017, 11:07 AM   #29
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I use a chartplotter for primary Navigation. iSailor for nav on my iPad and iPhone. And Garmin Bluecharts for planning/look ahead app on iPad.

Oh yeah....and I am a magnetic guy with a magnetic personality!!!...
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Old 05-04-2017, 12:14 PM   #30
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If iSailor had an easy way to measure a point to point distance and the tides and current lookups, I would use that one just for its pretty charting.

David
Thanks for your opinions on this stuff. Regarding point-to-point with iSailor, I just drop a couple of waypoint pins on the chart with the routing tool and the distance/heading are displayed. I can drag the pins around to suit my needs/guesses on any particular leg.
Here's how it looks for a couple of legs....
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Old 05-04-2017, 04:00 PM   #31
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All true, but what reference do you use for navigating? How do you get true north on your plotter? How do you know where true north is?

And a movement in 685 miles in 150 years might mean that you'll miss the dock by 3 inches.

I'm not convinced but sure have an open mind to a reasonable explanation.
I sure you're aware that to keep an accurate reading of magnetic north you need to adjust your compass as you move from place to place as you travel.

Plus declination changes even for your local cruising grounds over time.

Were as true north stays true north. Charts are orientated to true north, I set my plotters to show course up and it's traditional to plot in true north so it just works for me.

"As one moves across the surface of the globe, lines of constant magnetic declination are called isogonic lines. As the earth's magnetic field varies over time, the positions of the north and south magnetic poles gradually change. The magnetic declination at a given location also changes over time."
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Old 05-06-2017, 12:00 PM   #32
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I sure you're aware that to keep an accurate reading of magnetic north you need to adjust your compass as you move from place to place as you travel.

Plus declination changes even for your local cruising grounds over time.

Were as true north stays true north. Charts are orientated to true north, I set my plotters to show course up and it's traditional to plot in true north so it just works for me.

"As one moves across the surface of the globe, lines of constant magnetic declination are called isogonic lines. As the earth's magnetic field varies over time, the positions of the north and south magnetic poles gradually change. The magnetic declination at a given location also changes over time."
Capt Bill,
All true, and there's nothing wrong with operating in a "true" world. Most people use magnetic because it's just easier. For my ops, 90% of it is in an area where the declination (variation) is so small it wouldn't make a difference (Florida, 2d W). Heck, I'd have a hard time holding a heading within 2d.

Now, for folks doing the loop, you get a bit more declination up in the New York area (I believe it's in the 12 to 13d W range). Some chart programs plot the course in true so one would have to pay attention. And west coasters need to be aware. But if you do everything in magnetic there's little worry. If one follows a path on their chart plotter, a compass isn't even needed on the boat, nor is true north needed.

Also, I want my compass pointing toward mag north. I won't adjust it for declination. I may adjust for deviation, but probably not as I don't have the tools. But taking reading after making a course run good it's close enough.
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Old 05-06-2017, 02:09 PM   #33
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This is turning into an interesting discussion.
Here is a declination calculator : Magnetic declination calculator

To give you an idea, here is the declination for a few cities on the "loop"

New York City. 13 degrees W
Norfolk Va. 10
Chicago Il. 2
Tampa Fl. 3
St Louis Mo. zero
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Old 05-09-2017, 09:15 AM   #34
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This is turning into an interesting discussion.
Here is a declination calculator : Magnetic declination calculator

To give you an idea, here is the declination for a few cities on the "loop"

New York City. 13 degrees W
Norfolk Va. 10
Chicago Il. 2
Tampa Fl. 3
St Louis Mo. zero
Rossland,

That's interesting stuff, but I'm still in the camp of not seeing any importance to it. One should be aware of it, if whatever charting their using has true north numbers.

I would bet a mariner could do the whole loop and never once reference true north. It would all be magnetic, and that's my plan, unless there's some reason to do otherwise.

Years ago, route planning was done with drawing a line on a chart, and following that line, most often with visual reference. When one got out of line of sight I guess one had to reference something else like stars, moon or have a low freq receiver... don't know, beyond my skill level.

My background is aviation, and in the early years thing like low range non directional beacons and VLF Omega was used for long range. A bit later, inertial nav systems, then came loran and then gps. Suspect boating was similar. Even back then a lot of those systems were magnetic. We rarely used true north for anything other that perhaps planning. Today, it's ALL magnetic, with one exception, and that's when one gets north of about 70d going over the north pole. We would switch to a true north reference which worked fine.

I'm not into long range marine travel, as I suspect the majority of members on this forum are. Perhaps for the ocean crossing and north pole travelers, true north is used. Would be interested in hearing what the ocean crossing folks use, however.

For the vast majority of us, it's plotting a course on a gps map system and following the magenta line. I have thrown out all paper charts years ago (for any kind of travel), and never needed them.

Am I in the minority?
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Old 05-09-2017, 10:36 AM   #35
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Pilots use magnetic, because the VORs use magnetic.

Mariners are taught and use true. Every ship I've been on, has the gyro set up for true.
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Old 05-09-2017, 11:52 AM   #36
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I did not intend my previous post as advocating true instead of magnetic. I was simply providing information for anyone interested. Which mode you use, or even whether you use a compass at all is a matter of personal choice.
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Old 05-09-2017, 12:51 PM   #37
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Pilots use magnetic, because the VORs use magnetic.

Mariners are taught and use true. Every ship I've been on, has the gyro set up for true.
Nothern,

Good point, I've never been at the help in a ship so I'm not familiar. In the smaller boats I've been on from 70ft down, I see them occasionally, but pretty rare. What would be the advantage of setting it to true?
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Old 05-09-2017, 01:22 PM   #38
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Good point, I've never been at the help in a ship so I'm not familiar. In the smaller boats I've been on from 70ft down, I see them occasionally, but pretty rare. What would be the advantage of setting it to true?
While I like my chart plotter, I still use paper charts. Since they are based on True, I tend to think in terms of True instead of magnetic. Maybe if I finally enter the current century and get away from paper charts entirely, I may start to change the way I think.

FWIW, when I flew I was still doing route planning with sectionals and a pencil. I would then correct for the declination and take off. But that was many, many years ago when a VOR the height of navigation technology.
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Old 05-09-2017, 01:41 PM   #39
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Another happy Navionics user here...
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Old 05-09-2017, 03:23 PM   #40
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"I don't always use bearings, but when I do, I prefer true."

Most days on the boat I don't use bearings at all - I'm just navigating from one waypoint to another using electronic charting, or line of sight. I did make a float plan for my delivery from Ketchikan to San Francisco Bay, including all course bearings (true).

For the record, I've used paper charts and DR in the past. Just curious - what are people doing with bearings these days?

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