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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #51  
Old 02-06-2014
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Re: Magnetic Variance

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Originally Posted by sck5 View Post
Rarely do I ever hear anyone give a position in anything but lat/long. In Chesapeake Bay people will often say things like "off Lookout Pt" or "a mile east of red 34" but never have i heard anyone give an exact bearing in either true or magnetic. It might be important in theory and yes, I learned to do it like everyone else but it just doesnt come up very often in real life unless you are still firmly in a paper chart only universe. Most of us arent any more.

Sure, it is a good thing to be ready for disaster to strike but do you REALLY keep a dead reckoning going on a long passage when you can simply read off the lat/long whenever you like and write it in the log? I think a lot of folks are piously repeating what their lessons told them was "proper" but which is a lot of work for a less accurate result.

It is a good idea to remember WHY our teachers told us to do all these calculations. It was to know our position with as much accuracy as possible. Again, I can do it, but why would I waste time with that when I have 4 redundant GPS's which will tell me my position with 10ft. accuracy? It is especially pointless when I am hundreds of miles from land and seem to only rarely have a wind fair enough to head directly toward my goal.
when you give a bearing, you normally give it from a known point, just like you just did. Red 34. You see your point, you glance at your compass and give your bearing from in magnetic. Simple.
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  #52  
Old 02-06-2014
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Re: Magnetic Variance

Quote:
Originally Posted by sck5 View Post
Rarely do I ever hear anyone give a position in anything but lat/long. In Chesapeake Bay people will often say things like "off Lookout Pt" or "a mile east of red 34" but never have i heard anyone give an exact bearing in either true or magnetic. It might be important in theory and yes, I learned to do it like everyone else but it just doesnt come up very often in real life unless you are still firmly in a paper chart only universe. Most of us arent any more.

Sure, it is a good thing to be ready for disaster to strike but do you REALLY keep a dead reckoning going on a long passage when you can simply read off the lat/long whenever you like and write it in the log? I think a lot of folks are piously repeating what their lessons told them was "proper" but which is a lot of work for a less accurate result.

It is a good idea to remember WHY our teachers told us to do all these calculations. It was to know our position with as much accuracy as possible. Again, I can do it, but why would I waste time with that when I have 4 redundant GPS's which will tell me my position with 10ft. accuracy? It is especially pointless when I am hundreds of miles from land and seem to only rarely have a wind fair enough to head directly toward my goal.
I see the point you are trying to make but it is still a good thing to know. I happen to like paper charts. If "most" others don't, well, that's all well and good but has absolutely nothing to do with me or my own preferences. I also like the accuracy of GPS. I think they both have their place. I also think it a wise precaution to keep a track on a chart and knowing how to do these conversions is necessary in order to do that. You said you can do these calculations. Well, I'm just learning. As to the "why" I want to learn them, I explained that in my previous posts. Anything will be pointless if you see no value in it.
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  #53  
Old 02-07-2014
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Re: Magnetic Variance

Thank you all who are helping to agree that it is OK to use all best knowledge, and technology we have for safe navigation. Most of time as beginner I am staying very close to visual reference of known land. Due to lot of factors this can be confusing.
Especially when judging distances over water. In this case charts, and last known position on it clears confusion between visual reference, and what chart plotter is showing. Practice, practice, and enjoy doing it especially in fair weather, as they say.
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Old 02-07-2014
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Re: Magnetic Variance

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Originally Posted by Osprey 26 View Post
Thank you all who are helping to agree that it is OK to use all best knowledge, and technology we have for safe navigation. Most of time as beginner I am staying very close to visual reference of known land. Due to lot of factors this can be confusing.
Especially when judging distances over water. In this case charts, and last known position on it clears confusion between visual reference, and what chart plotter is showing. Practice, practice, and enjoy doing it especially in fair weather, as they say.
You're right Osprey. It's all good. I think it really falls back to personal preference. I like being able to look at a chart and letting my eye pick out the details I need at the moment from within the big picture. Chartplotters get expensive as the size of the screen goes up. For me, even the big ones I've seen lose the fine details if you zoom out, leaving you the choice of looking at either the big picture OR displaying the details, but not both. Some people may be able to get what they need off of those small screens but not me. I just prefer a chart.

My sailing was done on Kentucky lake and at no time was I out of sight of land. I carried my handheld Garmin GPS but did practically all navigation with my chartbook, a compass, and my eye. The GPS came in handy at night or during foggy conditions. I wouldn't want to be without either.

If you don't deal with measurements on a daily basis, I would suggest getting a cheap rangefinder. They are pretty accurate out to 500 to 800 yards on a reflective surface. Once you get good at judging distance out to 100 yards you can use simple addition to count how many 100 yd increments are between you and your target. If you keep an accurate position of your boat, just pay attention to how far an object appears to your eye, then measure it on your chart. After some time, your eye will become more accurate. Hope that helps.
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  #55  
Old 02-07-2014
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Re: Magnetic Variance

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Originally Posted by Dean101 View Post
The GPS came in handy at night or during foggy conditions. I wouldn't want to be without either.

If you don't deal with measurements on a daily basis, I would suggest getting a cheap rangefinder.
The best tool for both fog and measuring distance is radar. If I had a forced choice between a chartplotter and radar, I would choose radar.

I have used radar to anchor in fog. I just pick a spot with sufficient distance to the other vessels. Very slick.

When underway in restricted visibility radar will pick up other vessels and objects, a chartplotter will not.
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  #56  
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Re: Magnetic Variance

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Originally Posted by jackdale View Post
The best tool for both fog and measuring distance is radar. If I had a forced choice between a chartplotter and radar, I would choose radar.

I have used radar to anchor in fog. I just pick a spot with sufficient distance to the other vessels. Very slick.

When underway in restricted visibility radar will pick up other vessels and objects, a chartplotter will not.
Totally agree. Radar would have shown the ship that almost ran us down one dark night going out the San Francisco ship channel. Our boat, shown below, had only a compass & a radio direction finder.

It was our perception that radar was "too expensive", which was wrong.

"How much is your life worth?"

Paul T
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  #57  
Old 02-07-2014
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Re: Magnetic Variance

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Originally Posted by dabnis View Post
Totally agree. Radar would have shown the ship that almost ran us down one dark night going out the San Francisco ship channel. Our boat, shown below, had only a compass & a radio direction finder.

It was our perception that radar was "too expensive", which was wrong.

"How much is your life worth?"

Paul T
Paul--With all due respect, considering the draft of your yacht, you really had no need to be in the ship channel at all, eh? Having been raised sailing on SF Bay, one learned early on, that it was wise, under almost all circumstances, to stay out of the ship channels/traffic lanes and particularly so at night or in fog or both. One could easily sail/motor point-to-point along the edges of the channels reasonably confident that one was not going to become a bug on the wind screen of ship. Crossing channels in fog was the greatest hazard/most nerve wracking event. One hove too and listened, quietly, for a ship's horn or the thumbing of their engines through the water and when opportunity presented itself by the quiet, went heck-bent for leather across the fairways. One's echo sounder always told the tale, and when one's depth came up to two or three fathoms, one was almost always in the clear. The experience was a good way to break a sweat regardless of how cold, dark and wet the fog, and, afterward, everyone had a good laugh about the experience, in relief, over hot Irish Coffee.

FWIW...
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Last edited by svHyLyte; 02-09-2014 at 08:04 AM. Reason: amendment, correct typo
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  #58  
Old 02-08-2014
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Re: Magnetic Variance

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Originally Posted by svHyLyte View Post
Paul--With all due respect, considering the draft of your yacht, you really had no need to be in the ship channel at all, eh? Having been raised sailing on SF Bay, one learned early on, that it was wise, under almost all circumstances, to stay out of the ship channels/traffic lanes and particularly so at night or in fog or both. One could easily sail/motor point-to-point along the edges of the channels reasonably confident that one was not going to become a bug on the wind screen of ship. Crossing channels in fog was the greatest hazard/most nerve wracking event. One hove too and listened, quietly, for a ship's horn or the thumbing of their engines through the water and when opportunity presented itself by the quiet, went heck-bent for leather across the fairways. One's echo sounder always told the tail, and when one's depth came up to two or three fathoms, one was almost always in the clear. The experience was a good way to break a sweat regardless of how cold, dark and wet the fog, and, afterward, everyone had a good laugh about the experience, in relief, over hot Irish Coffee.

FWIW...
Points well taken. On that particular night the bar was breaking & we were concerned about going up Bonita channel. We were going up the far north edge of the channel trying to stay out of anybody's way. It was very rough, even in the channel and we got pre-occupied with what was in front of us. For some reason, I looked back and saw a wall of lights closing on us fast, no whistle, no sounds, nothing, although the "screaming Jimmy" in our boat did put out some noise. We had a big steel diamond shaped radar reflector in the mast. If the ship saw us, they made no mention of it. I don't know why the ship was that close to the edge of the channel, but it was, took us completely by surprise, we thought we were about as far to the edge as we could get. We did not have a fathometer or radar, which would have shown the ship closing on us.

Yes, I know, "penny wise and pound foolish". We underestimated the cost of going into that business, but that was a poor excuse for not being properly equipped. Looking back on it, we shouldn't have even considered going out that night, bad call, lucky to be here. 1964 was a long time ago.

Paul T
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Old 02-09-2014
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Re: Magnetic Variance

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Originally Posted by dabnis View Post
.... 1964 was a long time ago.

Paul T
Yes, but it doesn't seem so, eh? I presume you remember Valhalla? (Sally Stanford's gin joint/bordello in the cove on the south end of Sausalito.) That was a good time, eh? (If you recall, Sally ran for, and was elected, mayor on the grounds that since politicians all proved to be whores anyway, the public should have the right to know they were voting for one to begin with. She actually did a pretty good job.)
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Re: Magnetic Variance

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Originally Posted by svHyLyte View Post
Yes, but it doesn't seem so, eh? I presume you remember Valhalla? (Sally Stanford's gin joint/bordello in the cove on the south end of Sausalito.) That was a good time, eh? (If you recall, Sally ran for, and was elected, mayor on the grounds that since politicians all proved to be whores anyway, the public should have the right to know they were voting for one to begin with. She actually did a pretty good job.)
Oh, yes, I remember her well, good fodder for the papers at that time. We kept our boat at Fisherman's Warf, a ladder & two pilings to tie up to, "what float?"

Later we kept our sailboat at Clipper Yacht Harbor, basin # 2 for ten years. We called it "cyclone alley" in the afternoons during the summer. One chance to get it docked right, one chance.

OK, here is a memory challenge for you. Who was the really big heavy hippie woman that always wore a MuMu and ran a restaurant, in North Beach, I think, then later moved it to Sonoma? Something like "Big Momma"?

Your prize will be determined later.

Paul T

Senior moment flash? Anita's Galley? or something like that?

Another flash: Juanita Munson? Juanita's Place, Galley? IIRC, a lot of the San Francisco "movers & shakers", like Herb Caen & Melvin Belli used to go there. As a telephone repair man, I went to Melvin Belli's residence, a "Community Apartment", now called Condos, I think. Very interesting person.

Bingo:

http://www.sfgate.com/bayarea/articl...es-2528141.php

Paul T

Last edited by dabnis; 02-09-2014 at 12:05 PM.
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