Good Nav Program for IPad

[Capt.Bill11]

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."

 

[Seevee]

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.

 

[Rossland]

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

 

[Seevee]

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?

 

[Northern Spy]

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.

 

[Rossland]

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.

 

[Seevee]

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?

 

[dhays]

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.

 

[Moonfish]

Another happy Navionics user here...

 

[Britannia]

"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?

Richard

 

[Seevee]

"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?

Richard

Richard,

Have no clue what people are doing with bearings. A bearing is simple a direction from one point to another. Could be magnetic or true. Perhaps good for a cross reference. I never use them. not needed. My bearing will be visual for the most part... "I see the building, bridge or whatever as a cross reference to my course.

 

[Seevee]

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.

Dhays,

Yea the pencil and sectional was the way I learned, too. Was good info for learning, I still use a sectional, but electronic as I'm mostly a VFR pilot. That went away in the late 80s when loran came in... and later with GPS. Loran was pretty popular on boats probably in the early 80s or so. I remember my first one that I used for lobstering at that time. Had a book with hundreds of loran positions on it. I thought it was the greatest thing.

When GPS came in, it changed the rules for marine navigation. I've probably had 30 or 40 different units over the years and they just get better and better. I've never had one fail, while I've had charts that blew overboard, or where so scratched up they couldn't be read.... so I don't keep paper charts on board for a back up any more... they are a poor backup. I use a second IPad and a phone for a back up, but never needed them in the past 25 years of GPS.

 

[catalinajack]

Another vote for Navionics...

Plus one for Navionics. We bought our boat three years ago in Florida and drove her home to Maryland using only an I-pad and Garmin Blue Chart. I now have a chartplotter and an Android tablet with Navionics which, having used both, I found the Navionics far superior to Blue Chart.

If it's the embedded Active Captain that attracts one to Blue Chart spend 10 bucks for MX Mariner instead which uses NOAA charts that can be updated for free as frequently as you like. MX Mariner has Active Captain embedded.