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les strouds after earth survival

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It's always good to get back to the basics once in a while, just to refresh.  Great stuff Kim!!

 

 

Doc

 

 

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Ouch.  8| Video #5 was painful to watch.  Stroud's 100% wrong in what he saws about the shadow stick method. For those who don't know already, the shadow stick method allows one to determine an accurate EAST/WEST line, not a north/south line. It does not point north or south, no matter how you look at the stick, because the line that is created is aligned along an east/west axis. Of course, one can easily determine where north is by inference because using this method one knows that the north/south axis is perpendicular to the east/west axis and the sun will be on the southern side of the line (if you're in the northern hemisphere), but there is simply no way that the line itself can point to north or south as he says it does...unless perhaps he filmed this at either the north or south pole.

 

Here's an illustration that shows what I mean:

http://www.google.ca/imgres?imgurl=http://i.stack.imgur.com/GnFX7.png&imgrefurl=http://robotics.stackexchange.com/questions/550/how-to-determine-heading-without-compass&h=415&w=450&sz=43&tbnid=8JDiuYdIWozO7M:&tbnh=86&tbnw=93&zoom=1&usg=__gHZAsjpTVBUQu6zr0xNLjbzuYGY=&docid=4I2T89fSKUWM6M&sa=X&ei=Le3CUdTeFsjMqQHz6YHACA&ved=0CDMQ9QEwAA&dur=322

 

Hope this helps,

- Martin

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Im not so sure about that one Pine Martin. I didnt watch the video with my internet connection but Im thinking once you know one direction you know them all.

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I have to agree with Pine Martin. The shadow stick method only gives you a west east line. May be a bit of bad editing on the part of the video. The problem with using the sun for navigation is that the sun is always moving.

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Swede,

You're 100% correct when you say that to know one cardinal direction is to know the other four, but that's not the problem.  The problem is that the shadow-stick method doesn't point in any cardinal direction. You'll see what I mean once you're able to view the video.

 

For anyone who has seen the video but still doesn't understand the mistake, it's this:  The path of the shadows which one plots over a time interval with this method is always a straight line that runs along an east/west axis, but it doesn't tell you which end points east, which points west, nor which side of the line is the north side and which is the south side.  However, you can infer all of this with ease, but Stroud goofed it up in his video.  He thinks (incorrectly) that the stick runs north/south. It doesn't. It runs east/west.

 

Here's how it works:

When the sun begins its arcing path overhead the tip of the shadow always falls to the opposite side of the object casting the shadow, so in the morning the shadow is long and points west.  As the sun rises in the first half of the day, the shadow begins pointing north, but it shortens at the same rate.  After the sun reaches that highest point the shadow then grows longer again as the sun begins it's descent in the west, casting shadows that point east. The result is that the path of the shadow plotted on the ground is a straight line that runs truly east/west. This is the case no matter what time of year it is. It doesn't matter if it's winter or summer, or what hemisphere you're in. The only difference is that in winter the sun is lower and so the shadows are all longer, but they don't produce a different path or direction of shadows. The path traced will still be a straight line that runs truly east/west.  Consequently, the line doesn't point to any cardinal direction. It's just a line on the ground that's oriented along an east/west axis. 

 

So how does one determine a specific cardinal direction? By simple inference: One just has to remember that in the northern hemisphere (ie: north of the equator) the shadows fall north of that east/west line (because the sun is always on the south side of the line). So, just stand with your toes at the line with the sun behind you and you'll be facing north (or south, if you're in the southern hemisphere). Once you know where north is, you know where south is (and vice-versa), and you in turn know where east and west are.  But the stick doesn't point to a cardinal direction and it never runs north/south.  That would be a geometrical impossibility.

 

So, what Stroud did wrong here was misremember the axis of orientation of the shadow's path and he, inexplicably, thought one end of the stick pointed north and the other south. In fact, neither end points north or south.  My hunch is, he'd never actually used this technique or else never quite understood it and was just relying upon a faulty recollection of how it works.

 

I don't think the suggestion that this was some editing blunder is correct either, because you can clearly see Stroud pointing along the axis of the stick on the ground (which marks the shadow's path) and he says, " "This stick points directly north..."  And then he added that the other end points south.  But it is simply impossible for such a technique to ever produce a line that is oriented north/south, much less know which end is north and which is south. 

 

Hope this helps,

- Martin

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I would agree with you PineMartyn, what I would say is that anyone that has ever done any form of navigation using the sun should have the common sense to know the sun is to the south in the northern hemisphere and in the north in the southern hemishpere. Also what he says about keeping the sun to one side of your face while hiking is going to make walk in a curve too, just a wider one!

When the shadow stick is used correctly there are only two places on the planet it wont work at two times of the year, within the Arctic circle and the within the Antarctic circle during summer or winter as the sun doesn't set during summer and doesn't rise in the winter.

 

And another point, the sun moves westward, thus giving you the east west axis, however it doesn't give you north-south, or does it? After he marked his three points and got his east west axis the line he marked was to one side of the shadow stick, and if you know enough about direction it'll show you which hemisphere you're in. In the case of Les, he's in the northern hemisphere.

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Im thinking because Ive used this in northern Canada more then once, mid day or about is the worst. Early the sun comes up in the east that tells me all I need to know. There again mid day can get confusing. At best its a general direction technique. Keep the sun, if its shining, over your shoulder or behind you what ever works for you. Ive never took off in the Canadian forests with out a compass so Ive really never had to rely on the sun but I know in the morning if Im walking into the sun Im going east.

 

I usually venture out from a road or lake. If I know the road runs east and west and I go away north all I have to do is go back south. I cant miss it. I may not know to go right or left by the time I hit the road but Im at least on the road. The same holds true for a lake and that has happened more then once.  :P  It all looks the same.  :D

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ive taught many a cubscout and boy scout that method.  we teach them a phrase.  Never Eat Slimy Worms (N,E,S,W)  It helps them figure out the directions.  I always tell them that the first rock you place on the point of the shadow is the worm. after that its pretty easy.  :)

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ive taught many a cubscout and boy scout that method.  we teach them a phrase.  Never Eat Slimy Worms (N,E,S,W)  It helps them figure out the directions.  I always tell them that the first rock you place on the point of the shadow is the worm. after that its pretty easy.  :)

 

That's a good little mnemonic device.  I will be going canoeing with my young niece this summer and she's never done anything outdoorsy.  I'll be passing this trick along to her.

Thanks,

- Martin

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That's a good little mnemonic device.  I will be going canoeing with my young niece this summer and she's never done anything outdoorsy.  I'll be passing this trick along to her.

Thanks,

- Martin

cool  :thumbup:

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