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Old 06-01-2009, 10:51 AM   #21
Neil
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Speaking of pin-point accuracy, about 10 years ago my buddy and I were winter camped in Quebec and for our daily bushwhack decided to aim for the tip of a very narrow bay on a lake about a mile away. We just wanted to see if we could actually succeed in coming out at that pin-point.

We had a 1:50,000 topo map and small Silva compass and we walked about 20 feet apart, the compass bearer in the back. We sighted on trees and were pretty impressed when we did come out at the exact spot we had chosen.

From one mile away how many degrees of arc subtend 10 feet?


Drawing grid lines on the map is a great technique. It only takes a minute and simplifies things greatly in the field. Using a compass with no declination adjustment allows me to freely switch back and forth from grid to magnetic mode in my head. Perhaps you can do the same thing with an adjustable compass too?
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Old 06-01-2009, 11:03 AM   #22
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I always carry a spare compass. My primary one set for true north with the declination and the back-up defaults to magnetic north. I can always set the declination for the second in the field in the event of a lost or broken primary compass. Or use the back-up if I prefer to work with magnetic North.

Just out of curiosity, if your using a GPS do you use true or magnetic north?
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Old 06-01-2009, 11:50 AM   #23
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Quote:
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From one mile away how many degrees of arc subtend 10 feet?
(theta radians)=s/r
10/5280 = about a tenth of a degree.
Pretty impressive, but unless you were wearing a hood viewing only the compass undercover so that you couldn't use any terrain clues, I'd say you got lucky.

But when I teach this stuff and set a student free on a wild bushwhack, they are impressed when they find the goal. I'm happy when I finally see "the light turn on" when they realize this stuff actually works.
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Old 06-01-2009, 11:55 AM   #24
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My primary compass is a Silva Ranger, and I use the declination adjustment on the compass. I like the "set it and forget it" nature of that approach. I set it for the area I am in, and then I forget all about "Magnetic/Geographic" confusion. I find that method much easier to teach, also. Lots of lines all over the map just reminds beginners that they are confused every time they look at it, and makes things look complicated, when they are still trying to master the basics of sighting an object, selecting a route, etc. Set it / check it in the morning, and forget it for the day.

But I know a lot of respected instructors use the lines. That's just not the way I learned.
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Old 06-01-2009, 11:56 AM   #25
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Just out of curiosity, if your using a GPS do you use true or magnetic north?
Almost always magnetic.

This makes for good brain exercise when used in conjunction with a map without magnetic grid lines. They say it's good for aged people to keep challenging their brains with various cerebral exercises.

What I'll often do is determine a magnetic bearing using the gps and dial it in to the compass directly. Then I'll use the compass and map to where I want to go. If I've done a lot of drifting and detouring then I'll take a look at the GPS and dial the new bearing in to the compass.
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Old 06-01-2009, 12:18 PM   #26
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Wldrns,

Let's cut to the chase - you've gone from originally claiming "greater advantage" of mag. meridians over declination adjustable compasses to, now, "just as accurate methods". I'm glad you can see my points.

Neil,

Sure, I would draw my own N/S lines if I run into a map with none. For instance, I'm looking at Five Ponds NE Quad 1:24000 (GN 8 minutes), Loon Lake 1:24000 (GN 39 minutes) and Debar Mtn. 1:24000 (GN 34 minutes), where, if I using them to bushwhack I would draw grids. In all those cases, I would ignore GN as it is less than a degree.

IF Grid North was BEYOND a degree I would still draw "True North" grid lines and simply adjust my compass to take the large GN into account.

However, I'm looking at club maps in or near the Whites in New Hampshire, the Adirondack Park metrics and my maps for up here in and around Ottawa and the Gatineau Park, all with grids, so I'm just saying there's lots of topos out there with them.

Finally, use this table to convert degrees to units of length:

FOR A LEG ONE KILOMETRE LONG

1 degree - 18 metres
2 degrees - 35 metres
3 degrees - 52 metres
4 degrees - 70 metres
5 degrees - 88 metres

To convert a kilometre to a mile, multiply kilometres by 1.61; to convert from metres to feet mulitply metres by 3.28.

Hawk - I don't use GPS.

Cliff
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Old 06-01-2009, 02:06 PM   #27
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Whatever works best for you

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Different strokes for different folks.

I've found that what I'm most comfortable with, works best for me. Sometimes that may be what is perceived as the "more difficult" way, but everyone's mind "adjusts' differently.

I have used the map method as Wldrn's suggests and it works fine. But I prefer to adjust the declination on my compass & work that way.

It "fits" me better. If that makes sense.

Whats cool here is that we're learning two different methods to achieve the same goal.

I would add that I am most comfortable in the field when i have studied my map a lot at home before I ever undertake the hike. It gives me a "sense" of what to look for and where I am, often without having to use the map or compass as often.

Hawk

Hawk
I don't use either of these methods, but prefer a different one completely. I think the point here is that there is more than one way to navigate with map and compass and the best way is the one that works best for the navigator.
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Old 06-01-2009, 03:44 PM   #28
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John,

If you don't mind, what method or variation on map and compass do you use?

Sometimes these forums can be good for learning a few things!
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Old 06-01-2009, 04:14 PM   #29
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I don't use either of these methods, but prefer a different one completely. I think the point here is that there is more than one way to navigate with map and compass and the best way is the one that works best for the navigator.
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John,

If you don't mind, what method or variation on map and compass do you use?

Sometimes these forums can be good for learning a few things!
What he said.
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Old 06-01-2009, 04:43 PM   #30
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Wldrns,

Let's cut to the chase - you've gone from originally claiming "greater advantage" of mag. meridians over declination adjustable compasses to, now, "just as accurate methods". I'm glad you can see my points.
Apples and oranges. The concept of "greater advantage" is quite different from being "just as accurate". I believe that others and I have indicated that there's more than one way to skin this cat, and each can be "just as accurate" provided you know what you are doing. The "greater advantage" point, if you missed it, was that the time spent in drawing the lines offers a fine opportunity to study the map and landforms at the same time, prior to reaching the trailhead. Something any competent instructor of precision navigation techniques will surely advocate. Better to be confused and to think about potential route problems with solutions preplanned at home than to be tired, cold, and bug bit with the sudden appearance of an unexpected beaver marsh in your point to point path. Accuracy and greater advantage go hand in hand, but are they not the same animal.

In the training course I teach I am talking about map features in front of the students and of the field adventure about to happen while the group of students line their maps. This will be my 19th year with some 25 students in each class. Many navigation and equipment use questions come up and are answered that would never have been asked had we simply headed with map in hand out into the woods with screwdriver and compass ready to adjust. When finished I am sure they fully understand the underlying purpose of the technique, and it solidifies in their mind the reason and interplay of human perception and the physics of navigation. It's always better to understand from first rational principles why we do something, rather than to memorize nonsensical mnemonics and tasks. Meanwhile they have learned to conceptualize landforms with routes and alternates planned as they pour over the map in detail. They ask questions, I ask questions, all get answered, all get understood. Then all are tested over 4 days deep in the backcountry where it counts. None have complained that the time drawing lines was wasted, that the map is cluttered, or the technique is not understood and works well.

I certainly do not neglect talking about the declination adjustment screw that many but not all students have on their orienteering style compasses and that technique, should a map suddenly appear in their hands with a grid overlay... but I point out the greater advantages of what we have done over the past time just spent by thought and discussion from drawing of lines.

I also teach how to orient the map itself to TN while placed on the ground using the declination value along with a zero declination compass, whether or not there are lines drawn or a compass screw adjustment. This technique has its own different "greater advantage" in properly visually orienting the landforms on the map with those seen on the land itself, especially when there is a vista of multiple distant points. If never seen before it's quite an eye opener to see that every physical feature is in its proper relative position from map to ground. They learn how to use an unprepared map without lines of any kind and a simple compass without declination adjustment to be "just as accurate" with this method, though it requires an extra few steps in time to set up each time a course is measured.

I saw some other instructor's post online one time... where he said that he doesn't line his map simply because he doesn't have the time, he usually buys his maps while traveling to the trailhead. Turned me off completely. Might as well use a gps and blindly follow a straight course between two points without taking time to interpret a route or enjoy anything of landforms in between.

Therefore I am still claiming the greater advantage in navigation by lining and concurrent map study if you choose to partake of it. Accuracy is as it always was with the same equipment and any modern method.... IF you also take time to completely understand what you are doing and what you are measuring and from what reference you measure. If you don't understand what measuring from the "north-south lines" already drawn on the map means, then you also lose out on being "just as accurate".
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Old 06-01-2009, 04:55 PM   #31
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I use about four different techniques in varrying orders and blends.

Sometimes I'll have map and compass only (no lines drawn), and on others I'll sit back and allow myself to be guided by the GPS (while keeping an eye on the map). GPS has lied to me a couple of times allthough it is usually deadly accurate. Enough so to bushwhack at night with it.

In between there is the map with "Wldrns lines" drawn on it and a blend of GPS and map/comapss.

I like to mix it up for variety's sake and also to keep myself sharp in several methods.

However, I have yet to accede to profficiency in celestial navigation techniques or to consider myself a stellar navigator.
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Old 06-01-2009, 05:22 PM   #32
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I keep it as simple as possible. I guide myself by the terrain and the map, while keeping an eye on the compass.
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Old 06-01-2009, 05:23 PM   #33
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I keep it as simple as possible. I guide myself by the terrain and the map, while keeping an eye on the compass.
In reality, that's how most navigation is done by the experienced people I know. You have to understand and interpret the terrain with the map. Good call.
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Old 06-01-2009, 06:06 PM   #34
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Wldrns,

You're right - I missed the "greater advantage".

I missed it because you've morphed this thread into "How to REALLY teach map and compass", which for you, among other things, means drawing magnetic meridians as a PREREQUISITE to conducting a complete, thorough, pre-outing map study.

Making a hard linkage between the two is misleading.
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Old 06-02-2009, 12:29 PM   #35
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In response to Neil's question yesterday, and, having never worked with a gridless topo, in my haste to respond I misphrased this part of it:

"IF Grid North was BEYOND a degree I would still draw "True North" grid lines and simply adjust my compass to take the large GN into account."

What I should have stated is in this summary:

If I was working with a grid free topo, I would draw N/S lines using the map's left or right margins, and with my compass adjusted for magnetic declination, use these lines as a reference in determining bearings;

For a map with grid which I plan to use, if grid/true north difference is less than a degree, I ignore this difference

If grid/true north difference is greater than one degree, I'll readjust the declination in my compass based on the difference between magnetic north and grid north.
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Old 06-04-2009, 10:36 AM   #36
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In the training course I teach I am talking about map features in front of the students and of the field adventure about to happen while the group of students line their maps. This will be my 19th year with some 25 students in each class.
Wldrns,

Where do you run this training course? It has been a long (too long) time since I've used my navigation skills and they are more than a little rusty. I'd like to get off the trails, but don't have the confidence to just plunge in. A training course with some classroom and field work would be a great way to dust off the skills.
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Old 06-04-2009, 10:57 AM   #37
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Wldrns,

Where do you run this training course? It has been a long (too long) time since I've used my navigation skills and they are more than a little rusty. I'd like to get off the trails, but don't have the confidence to just plunge in. A training course with some classroom and field work would be a great way to dust off the skills.
You need to be in some way attached to a recognized organization with interest in outdoor education and leadership. See this link.
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Old 06-04-2009, 02:00 PM   #38
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John,

If you don't mind, what method or variation on map and compass do you use?

Sometimes these forums can be good for learning a few things!
I use a simple 2 degree increment baseplate compass without dclination adjustment.
1) After aligning the baseplate in the desired direction of travel,

2) I rotate the bezel and align it (the bezel lines) to the UTM grid or if not present to the side margins of the map. Alot of the time I'm using copies of the USGS topo in a ziploc. If the area of travel is not close to the edge of the map, then I reasonable precisely fold the map and use the crease as a N/S line.

3) Then I adjust for declination. Now here is the different part: You may not be able to add or subtract when hypothermic. And in winter I like to tread that fine line of temperature regulation meaning I've been at the point where adding or subtracting would require a long period of concentration (10sec?). If you remember that the adjustment is a bezel rotation by 6 or 8 lines then it comes down to direction of rotation. For me, I envision myself standing looking north. In an ideal world, (the map), north is straight north. In the field, (the magnetic world) the MN is located more towards the center of Canada. So to go from map to field rotate the bezel towards the center of Canada. Field to map is opposite using the same logic. It works on either coast. As long as you know the 0 line goes through OH and FL then you know the direction for all the US. Any map (New Zealand, Switzerland, Italy) that shows the MN and N arrows will visually confirm the direction of rotation. For me, I look and think, oh just like the east cost or the west coast. I don't concern myself with "east declination" or "west declination" or adding or subtracting, or drawing lines or adjusting compasses. I move hiking areas too ofted to be futzing with a declination adjusted compass, but that's for me. It's a visualization method. And if someone were to ask me: do you add?, I would think about the positon of the bezel before and after the rotation and come to the answer.

4) lastly I read the bearing aloud - it allows me to remember it and on some occasions (like when I use the wrong fold or edge) my companions or I will think that doesn't sound right. Such as when your climbing the east side of the mountain, expecting a bearing of 270ish and you get 200.

This is a good method for people that don't do math well or don't like to draw lines on their maps.

The other advantage is that I can grab a map, any map, and immediately navigate from/to X in a few seconds. Comes in handy whey you have 770 mountains to climb and 2 or 3 maps of each.

Last edited by John H Swanson; 06-04-2009 at 02:06 PM.. Reason: more info
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Old 06-04-2009, 02:15 PM   #39
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For me, I envision myself standing looking north. In an ideal world, (the map), north is straight north. In the field, (the magnetic world) the MN is located more towards the center of Canada. So to go from map to field rotate the bezel towards the center of Canada. Field to map is opposite using the same logic.... It's a visualization method.
I do the same thing when I don't have prepared maps for whatever reason. I always visualize that the zero declination line passes through Chicago and New Orleans. That tells me in a visual way which way to turn from magnetic north to face true north. Math is not involved. I love math, but when hypothermic or dead tired it is all too easy to make a disastrous mistake.
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Old 06-04-2009, 02:43 PM   #40
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I do the same thing when I don't have prepared maps for whatever reason. I always visualize that the zero declination line passes through Chicago and New Orleans. That tells me in a visual way which way to turn from magnetic north to face true north. Math is not involved. I love math, but when hypothermic or dead tired it is all too easy to make a disastrous mistake.
I checked, your more right then me. New Orleans yes, Chicago no. More west than Chicago. I either case it's in my best intereste to avoid hiking in the Mississippi area
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