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Old 07-01-2013, 12:27   #181
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Re: Distinct Activities: Shackled by a Common Name?

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Originally Posted by Dockhead View Post
We may be talking in circles, but here goes.............
I certainly agree that there has been much, "talking in circles". It's strangely common to see so much posted in agreement.

Everyone seems to agree that it's wise to use the latest navigation tools.
Everyone seems to agree that it's wise not to rely on too few tools.
Everyone seems to agree that it's wise to have navigation knowledge.
Everyone seems to agree that there are limitations to navigation tools.
Everyone seems to agree that there are inaccuarcies & approximations.

'weird how some seem to be marching to different drummers!
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Old 07-01-2013, 23:33   #182
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Re: Distinct Activities: Shackled by a Common Name?

Okay, then if I understand Andrew's position, as clarified by minaret, if I use a chart plotter to navigate into a dangerous cove, and take a glance at the depth gauge and compare that information to the chart plotter, I'm navigating properly in the time honored sense.
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Old 07-01-2013, 23:40   #183
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Re: Distinct Activities: Shackled by a Common Name?

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Originally Posted by Jammer Six View Post
Okay, then if I understand Andrew's position, as clarified by minaret, if I use a chart plotter to navigate into a dangerous cove, and take a glance at the depth gauge and compare that information to the chart plotter, I'm navigating properly in the time honored sense.


Yes. But more importantly, if you are plotting a course between waypoints on a chartplotter and use a current chart to figure out the proper ferrying angle before even seeing a cross track error reading, you are properly piloting. Or if you plan to run a pass at slack tide, or cross a bar at slack tide, etc, etc.
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Old 08-01-2013, 00:38   #184
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Re: Distinct Activities: Shackled by a Common Name?

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Yes. But more importantly, if you are plotting a course between waypoints on a chartplotter and use a current chart to figure out the proper ferrying angle before even seeing a cross track error reading, you are properly piloting. Or if you plan to run a pass at slack tide, or cross a bar at slack tide, etc, etc.
I'm just going to throw more oil on the fire with this example --

Although I am a total fan of old-fashioned chart work, hand calculated tidal vectors, etc., etc., etc., I would never in hell "use a current chart to figure out the proper ferrying angle". If the current goes only one way and at one speed during the time of the passage, I would simply adjust the heading until the electronically calculated COG matches bearing to waypoint. I might even put the pilot on "Track" mode (I can hear the shudders of the Luddites). There is no chart-based method which comes close to the accuracy and convenience of these methods, for that situation.

If crossing a tidal body of water with varying speeds and directions of water, you don't calculate a "ferrying angle". You caculate set and drift for each hour of your passage at your estimated passage speed, and add it up to get a CTS -- course to steer -- to your destination (which for me is always one mile uptide of where I actually want to go, to give a margin of error). This is a pretty laborious job -- takes me a good hour to work out a plan for a typical Channel crossing, but I like to do it all by hand without using a calculator (I must sound like I'm contradicting myself, but I prefer to do all the math with a pencil in an analogue manner, because many of the calculations are guesses and approximations and I don't have nearly enough math to do numerical approximations on a computer). I do three complete sets of calculations -- one for 7 knots average, one for 8 knots average, and one for 9 knots average speed.

Then you steer that one course (or much better, put the pilot on that one course in its plain old "heading mode"), and pay no attention as the tide sweeps you back and forth. You check the accuracy of your calculations once every hour against XTE as calculated by the plotter -- if you do your vectors by hand, that's the result you get anyway for every hour's calculation -- cumulative set and drift in relation to the rhumb line should equal XTE as calculated by your plotter. You also must keep an eye on your passage speed -- if you are faster or slower than your assumption, it will throw everything out. I usually re-run the whole thing in the middle of the Channel and calculate a new CTS which, if everything has gone well, will not be more than a degree or two off the original one.

That's the way we do it over here. You use every electronics means at your disposal, but a big part of the job cannot be done by any electronic system whose existence I'm aware of.
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Old 08-01-2013, 01:03   #185
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Re: Distinct Activities: Shackled by a Common Name?

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I'm just going to throw more oil on the fire with this example --
A good example of where a paper chart comes in handy. Although this could be done on a piece of plain paper, using a paper chart can make you more aware of any hazards along the route.

Dockheads explanation of calculating a CTS when transiting an area with variable tidal streams is one I have trouble in getting across to some of my watch keepers, who seem to have a phobia about having to stay on the red line.
When at work, and towing, speed can be down to 3 kts, trying to keep to the line makes a longer passage, and at 3 kts and at close to full power, makes the passage much more expensive.
I have even more trouble trying to explain this to the guys on the rig being towed. They usually have a chart and a GPS and in some cases, actually use them. Quite often they call up and with some concern, ask why we are mile or so off the charted course line.
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Old 08-01-2013, 02:13   #186
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Re: Distinct Activities: Shackled by a Common Name?

When one is making a passage across tidal waters, as in the examples given, does the electronic magic box generate a course that is significantly different from that generated on paper by hand? If so, why?
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Old 08-01-2013, 02:14   #187
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Re: Distinct Activities: Shackled by a Common Name?

Gotta remember: IT'S JUST A LINE.
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Old 08-01-2013, 02:17   #188
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Re: Distinct Activities: Shackled by a Common Name?

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When one is making a passage across tidal waters, as in the examples given, does the electronic magic box generate a course that is significantly different from that generated on paper by hand? If so, why?
Absolutely. The electronic box -- at least my ones -- will only tell you what is the rhumb line to your destination. It can only tell you what is the shortest distance to your destination over ground.

If you are crossing tidal waters, you need the shortest distance over water. That is because your boat doesn't sail in the bottom; it sails on water. The shortest distance over water is a constant compass bearing.
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Old 08-01-2013, 02:47   #189
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Re: Distinct Activities: Shackled by a Common Name?

I see, for some reason I was thinking electronics were capable of adjusting for tide and current.
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Old 08-01-2013, 02:52   #190
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Re: Distinct Activities: Shackled by a Common Name?

Just to add my two cents. Somewhere up there someone mentioned that their plotter showed them as being in the yacht club when they were at the dock. My plotter shows me sailing directly across the breakwater when I enter Helsingborg harbor. About 15 meters too far to starboard. And it does it every time.

Unless i am sailing in familiar waters, I always check position against paper and I always use the Mark 1 eyeball.

I've also seen a number of boats sail directly aground, while following "the little black line"

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Old 08-01-2013, 03:01   #191
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Re: Distinct Activities: Shackled by a Common Name?

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Just to add my two cents. Somewhere up there someone mentioned that their plotter showed them as being in the yacht club when they were at the dock. My plotter shows me sailing directly across the breakwater when I enter Helsingborg harbor. About 15 meters too far to starboard. And it does it every time.

Unless i am sailing in familiar waters, I always check position against paper and I always use the Mark J eyeball.

I've also seen a number of boats sail directly aground, while following "the little black line"


The MarkJ eyeball.
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Old 08-01-2013, 03:17   #192
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Re: Distinct Activities: Shackled by a Common Name?

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Dood, learn to read, go back, and read Andrew's posts again. He never at any point said that if you use GPS you "aren't a real navigator". Quite the opposite, he himself uses GPS and thinks it's a good tool. What he said, many times repeatedly (and I can't understand why some of you keep trying to act like it's not what he said), is that if you use GPS "to the exclusion of all other methods", you aren't navigating. That means if the only tool for navigation you have aboard and know how to use is a chartplotter with GPS, you aren't a navigator (or more accurately to me, a pilot). This is a statement I think most of us can wholeheartedly agree with, and I don't see why so many of you insist on turning this into an argument about whether paper charts are better than GPS, as no one ever at any point suggested that was the case. Any navigator worth his salt uses all tools available, and guess what, some of the tools available aren't electronic gizmo's, and do things that an electronic gizmo can't, like a simple pelorus. Or your knotmeter. Quit trying to accuse the guy of being some sort of luddite, based on a couple of posts you clearly misunderstood.
Im sorry Minaret, I have been replying to this thread since teh beginning, You are wrong here, I never claimed the Op was a luddite. I merely rejected his ascertain that using GPS and chartplotters does not make you a navigator,

to quote him

"
Option A: do it yourself
Option B: get others to do it, and tell you the answer

Those "others" may be present on board, but more likely they're engineers, programmers, satellite technicians, mathematicians etc etc etc whom we will never meet. And they are "doing it" not in the sense that they work on the specific problem of our position, but in the sense that they've worked out how to do it in the general case, and how to make the fruits of their efforts available to us whenever and wherever we specifically require it"

This is clearly an argument that using electronics turns you into a numskull. ie "the others are doing it for you".


as your statement

Quote:
That means if the only tool for navigation you have aboard and know how to use is a chartplotter with GPS, you aren't a navigator (or more accurately to me, a pilot). This is a statement I think most of us can wholeheartedly agree with
This of course renders many modern bridges etc to the status of drivers, The fact is if you have a GPS and chartplotter, you still have eyes, you can still do visual fixs etc. It may not be optinium, but it does not mean your not a navigator

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Old 08-01-2013, 03:30   #193
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Re: Distinct Activities: Shackled by a Common Name?

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I see, for some reason I was thinking electronics were capable of adjusting for tide and current.

Looks like some can, although this example is PC based

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Old 08-01-2013, 03:32   #194
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Re: Distinct Activities: Shackled by a Common Name?

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If you are crossing tidal waters, you need the shortest distance over water. That is because your boat doesn't sail in the bottom; it sails on water. The shortest distance over water is a constant compass bearing.
huh, only if the tide is symmetrical.

I for one, only calculate CTS if I have good tidal stream data, in most places you do not. Equally I set a limit on how far my XTE should get as I have found if I get the CTS wrong, I can get out of position, often ending downtide of the destination. Id have to say that most people today are merely using XTE.

in many areas that I am familiar with , I merely run CTS in my head, ie I allow for a degree of tide, over a period, often just compensating for it in my head, then use XTE as a quide to my success. While I have taught the RYA YM night classes to many people, Im not a great fan of the "compute all the vectors " approach. The on water events often throw everything out and force repeated recalculations,

To get back to the argument, and Im at one with Dockhead. Im not arguing that the human can be weak willed and lazy, absolutely. I dont disagree with Andrew or anyone on that ground. I would argue that however the mere fact of using GPS and Chart plotter does not diminish the status of a careful navigator, whether or not he has paper aboard .

If the bones of this argument is that technology makes you lazy, I reject it, as I did when a similar thread argued that safety equipment makes you reckless.

The fact is that rarely today, do boat owners carry comphrensive paper charts, often its planning charts etc, few are fully "papered up" for alternative destinations etc, Hence often people with paper charts are still reliant on their plotters for detailed approach charts.


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Old 08-01-2013, 03:41   #195
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Re: Distinct Activities: Shackled by a Common Name?

Dave,

I agree that few are "papered up". For many reasons, amongst which are

cost
storage space when cruising long range

But let's face it, Position fixing (not navigation) with a GPS or plotter is far superior to a sextant, even for an expert. GPS is also superior to DR or even triangulation on 3 or more fixed points (by the time you have worked out the position - it has changed.

So I think we can all agree that in so far as positions are concerned - GPS is the clear winner.

RE: Navigation, which is an entirely different matter, the skipper needs to remain aware not only of his (her) position, but also his surrounding area, bottom, depth, currents, shipping lanes etc etc etc.

Alwmost all the data needed to navigate properly is available on a plotter, but plotters are difficult to keep a clear overview on, unless you have one with a mega large screen (or a repeater below deck).

So I generally use the paper for getting an overview and noting any exceptional issues (reefs f.eks), and check the plotter for position while sailing.

Both my wife and I occasionally go below and check the paper, if we are in really unfamiliar waters.
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