Hi, i have heard there is a method of estimating distance in navigation called ''The Finger Method'', (apparently taught to certain seviceman during WW2), you do something like look at finger at arms length and close one eye and multiply certain numbers to get correct distance of a particular location, does any one know of this method and if so give correct formula/instruction to use the technique correctly, i know it wouldn't be an exact measurement but is it reasonably close enough to be worthwhile or not in giving a rough estimate.
Estimating distance - ''The Finger Method'' - (Navigation)
- Thread starter Joonsy
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Hi Joonsy, this method does work well, the trick is to "calibrate your instrument". Into astronomy at all? Have a look-see at the section called "Estimating Angles by Eye" from the link below. Roughly, at arm's length a thumb is 2 degrees, your little finger is 1, a hand's width is 10 degrees and your outstretched palm from pinky to thumb is 20.
http://www.geocities.com/angolano/Astronomy/PIinSky.html
Worthwhile I think, if the stars are out tonight you can work this one right out. Then a little trig refresher and there are all kinds of things you can figure out by determining angles.
http://www.geocities.com/angolano/Astronomy/PIinSky.html
Worthwhile I think, if the stars are out tonight you can work this one right out. Then a little trig refresher and there are all kinds of things you can figure out by determining angles.
I did this as a lesson for the Cadets a few weeks ago.
Hold your thumb up at arms length
look at your target with your right eye only next to your thumb
Without moving your thumb, switch eyes and note the apparent lateral movement
Multiply the apparent movement by 8 to get an approximation of the actual distance.
It relies a lot on knowing how big the target is (a man is about 2 m tall, child is 1 m etc)
and it does improve with practise.
If I can find some of the links I'll post them up.
ATB
Ogri the trog
Hold your thumb up at arms length
look at your target with your right eye only next to your thumb
Without moving your thumb, switch eyes and note the apparent lateral movement
Multiply the apparent movement by 8 to get an approximation of the actual distance.
It relies a lot on knowing how big the target is (a man is about 2 m tall, child is 1 m etc)
and it does improve with practise.
If I can find some of the links I'll post them up.
ATB
Ogri the trog
Its explained here http://books.google.com/books?id=de..._dzaID&sa=X&oi=book_result&ct=result&resnum=2
This is in a book preview of Paul Tawrell. Looks quite easy, nothing more complicated than multiplying by 10. Also shows you how to do it with binocs. The book appears to have a lot of good info in it.
Hope this was what you were looking for.
This is in a book preview of Paul Tawrell. Looks quite easy, nothing more complicated than multiplying by 10. Also shows you how to do it with binocs. The book appears to have a lot of good info in it.
Hope this was what you were looking for.
How did I read that as 'estimating angles'
... anywho, what they said. With practise you can get pretty good. We used to have to do better than +/- 15% with naked eye distance estimates out to 2000 meters or so. +/- 10% with binos and within +/-5% using a scope(both had reticules). This seemed IMPOSSIBLE at first but with practise(alot I guess it was) this was no big deal. It's amazing what the brain is capable of if given half a chance. There are a couple of good tricks in Kephart's "Woodcraft", the section on Route Sketching. I think this book is available here, in the downloads section.
Hi folks, thanks for replies and forwarding links, very useful and i will give it some practice to see how i get on, it seems to rely on the amount of movement by your ''master eye'' (i once confounded someone as i'm left-handed with a right master eye), i am a little puzzled though as to multplying movement, it seems movement is only a few inches in ''visible'' terms but would be yards in actual real terms, i am presuming the distance estimated is from person to object and not an estimation of size of object one is looking at, at moment i can't quite see how the movement created by closing one eye is thought of in yards as it appears to be only inches to me when held at arms length, i obviously have to give it some practice, yes Bravo4 i am interested in astronomy, i can identify a number of constellations and individual stars but am relativley inexperienced and learning all the time, i have always found stargazing a magical experience and the question of ''where is the end of space'' always fascinates me.
I too am having trouble figuring out what it is your meant to multiply to get the distance. Today I looked out my window at a church tower I know to be approximately 3/4 of a mile away, did the eye thing and couldn't work out what I was meant to be doing. Actually If I think about it.. dangerous thing to do I know, what's with the holding up of the arm and thumb at all... no matter what you look at,with one eye and then the next, the "movement" between the two images will be the same, as your arm is the same length at all times?
OK no worries,
the movement you are estimating is the apparent lateral shift "at the target" - which has to be in relation to the estimated size of the target, so a church steeple is probably of unknown height and hence not necessarily a good thing to practice on.
Look across the room at something that you know the size of - books, crockery, ornaments, that sort of thing. When you estimate the shift, guess how many widths the object has moved and come up with a lateral distance to multiply by 8 (though tis could vary up towards 9.5 or as low as 7 depending on the individual).
You can try it with cars - most are around 4 foot/1.5 meters tall for an average small car or 2m for a 4x4.
The theory is based around the distance between eye and thumb - and eye to eye is about 8:1 qs already mentioned I think.
Still trying to find the links - oops.
ATB
Ogri the trog
You see, this is whats confusing me. You mention that you need to know the height of the target, but don't use it to measure the distance, you say to use the width. I know I am probably missing something, but why do I need to know the height of the target? I did this with a candle in my living room, it is just over a foot tall and 3 inches wide. it moved about 4ish widths. So by this anyone could tell me the distance? Seeing as I know it, as it's in my living room, this could prove interesting..
To me it seems if I know that, I can easily work out a rough distance by scale, and not wiggle my thumbs in the air, like I just don't care.
sorry had an old dance tune in my head..
You see, this is whats confusing me. You mention that you need to know the height of the target, but don't use it to measure the distance, you say to use the width. I know I am probably missing something, but why do I need to know the height of the target? I did this with a candle in my living room, it is just over a foot tall and 3 inches wide. it moved about 4ish widths. So by this anyone could tell me the distance? Seeing as I know it, as it's in my living room, this could prove interesting..
To me it seems if I know that, I can easily work out a rough distance by scale, and not wiggle my thumbs in the air, like I just don't care.
No worries Naqual,
Knowing the height of the target just gives you a size reference to work with that is of reasonable scale. Lets see if I can explain it......
Knowing that a man is 2 meters tall is easier to work with than say.... knowing his feet are 30cm long - if the percieved shift is a number of meters, rather than trying to work out how many 30cm footwear sizes are in the same horizontal distance, though both should work out to be a similar figure.
With your candle example, 4ish widths = (4 times 3 inches (wide)) times 8 equals 8ish feet away. Now try something for me, lay on your side and do the same thing using the height of the candle.... ( I recon it'll shift by 1 times its height) its just so you can avoid the 4ish X 3inches part of the calculation, if you already know that it is 1 foot high.
There are other methods of estimating distance, and like many things Bushy, use as many as you can to obtain your best guess answer.
HTH
Ogri the trog
Just got the measuring tape to double check things. The candle is 11 inches tall and 3 inches wide at a distance of 11 feet. The actual lateral distance between the two eyes is 11 inches, so knowing all that...
Distance to candle = length of difference X certain amount.
or
certain amount = Distance / length of difference..
CA = 132 / 11
CA= 12
heh.. works for that, however just checked with a smaller distance and was out by 10 inches or 20%.. hmmm I think this isn't working out too well for me here..
Distance to candle = length of difference X certain amount.
or
certain amount = Distance / length of difference..
CA = 132 / 11
CA= 12
heh.. works for that, however just checked with a smaller distance and was out by 10 inches or 20%.. hmmm I think this isn't working out too well for me here..
What we're missing is a good diagram. "Parallax" is the fancy name for all this. A couple of links explaining:
under "estimating distance outdoors"
http://www.phy6.org/stargaze/Sparalax.htm
under "Parallax, a relationship between angles and distance
http://www.eso.org/public/outreach/eduoff/vt-2004/Education/EduSheet2.html
we need to pretend we know all this here, google search results for "estimating distance finger method", #1 points guess where?
http://www.google.com/search?hl=en&q=estimating+distance+finger+method
under "estimating distance outdoors"
http://www.phy6.org/stargaze/Sparalax.htm
under "Parallax, a relationship between angles and distance
http://www.eso.org/public/outreach/eduoff/vt-2004/Education/EduSheet2.html
we need to pretend we know all this here, google search results for "estimating distance finger method", #1 points guess where?
http://www.google.com/search?hl=en&q=estimating+distance+finger+method
One might think the atmosphere was made transparent with this design, to give man, in the heavenly bodies, the perpetual presence of the sublime. Seen in the streets of cities, how great they are! If the stars should appear one night in a thousand years, how would men believe and adore; and preserve for many generations the remembrance of the city of God which had been shown! But every night come out these envoys of beauty, and light the universe with their admonishing smile.
Ralph Waldo Emerson
Emerson's "Nature"
http://oregonstate.edu/instruct/phl302/texts/emerson/nature-emerson-a.html
not much to do with parallax exactly, but I could not resist
Ralph Waldo Emerson
Emerson's "Nature"
http://oregonstate.edu/instruct/phl302/texts/emerson/nature-emerson-a.html
not much to do with parallax exactly, but I could not resist
Hi, am i right in thinking to estimate the distance then you have to know the height of a particular object to start with, for example if i wanted to know how far away a certain person was then i would be able to estimate the distance as i would have a rough idea of the height of the average person to begin with, however say i wanted to know how far away a particular hill was and had no map with me hence no idea of the height of that or any other hill in the vicinity, by placing finger on hill summit would i have to know the rough height of hill to be able to estimate the distance between it and myself, and if i had no idea of the height of that hill to begin with would it then be impossible to estimate the distance, you may lose a map or just not have one with you so you would not be able to know the height to begin with, if you must know the height of object for method to work it seems to be of little use in estimating distance of objects of unknown height such as hills but ok for objects of known height such as people, trees, buildings etc:, or have i got it completely wrong.
No that is basically right. In order for the above to work, you must be able to work out the distance between the your 'two' thumbs. if there is no way of doing that, then your up a creek with no paddle, with this method. I have to say I don't think this method is very reliable at all, it seems to create more work than is needed, as if I can see an object that I know the size of anyway, I don't need thumbs and angles and parallax to tell me what I can plainly see.
Can't say that I ever actually used this method either for practical purposes. I've worked as a land surveyor and range estimation was once a very important part of my army job, learned this technique(parallax) but never used it in the field. Very useful for range finding stars and such. If you are more interested in knowing the distance to an object than say, trigonometry, there are better ways.
Once you have an idea of what a man looks like at 100meters, then 200m, then 300m and on out you start to develope the range finding skill known as the "appearance of object method" or you can call it the "100 meter unit of measure method". This is a bona fide technique, you have to start by impressing on your mind what a "known" size looks like at a "known" distance. You can practice as you hike along, pick out a point down the trail and pace it off as you approach.
This skill goes along with knowing your "pace count" for land nav (and not just on a flat stretch but on uneven terrain, with a heavy pack, at night, when you're tired; your pace count alters.) There are several factors which can alter the "perception" of distance and this is certainly more art than mathematics, at least for me.
There are numerous ways to estimate range, if you are not bored to tears already here's another link. If you scroll down to section VI of chapter Four, of this here u.s. army FM 23-10 there is a section on range estimation. This is one of the better manuals on military fieldcraft techniques but kind of assumes you know this stuff already so doesn't go into alot of detail.
http://www.globalsecurity.org/military/library/policy/army/fm/23-10/ch42.htm#s6
As for losing a map in the field I was taught that this is an eternal sin and so not wanting to be damned to eternal hellfire I keep my maps on my person along with whatever pieces of key survival gear I can cram into my pockets. If somehow my pack and it's contents are lost, brown stuff all over the fan, that map could be a big part of what saves my bacon. Or canned chicken depending on the which vauge reference to a BCUK thread you prefer.
Once you have an idea of what a man looks like at 100meters, then 200m, then 300m and on out you start to develope the range finding skill known as the "appearance of object method" or you can call it the "100 meter unit of measure method". This is a bona fide technique, you have to start by impressing on your mind what a "known" size looks like at a "known" distance. You can practice as you hike along, pick out a point down the trail and pace it off as you approach.
This skill goes along with knowing your "pace count" for land nav (and not just on a flat stretch but on uneven terrain, with a heavy pack, at night, when you're tired; your pace count alters.) There are several factors which can alter the "perception" of distance and this is certainly more art than mathematics, at least for me.
There are numerous ways to estimate range, if you are not bored to tears already here's another link. If you scroll down to section VI of chapter Four, of this here u.s. army FM 23-10 there is a section on range estimation. This is one of the better manuals on military fieldcraft techniques but kind of assumes you know this stuff already so doesn't go into alot of detail.
http://www.globalsecurity.org/military/library/policy/army/fm/23-10/ch42.htm#s6
As for losing a map in the field I was taught that this is an eternal sin and so not wanting to be damned to eternal hellfire I keep my maps on my person along with whatever pieces of key survival gear I can cram into my pockets. If somehow my pack and it's contents are lost, brown stuff all over the fan, that map could be a big part of what saves my bacon. Or canned chicken depending on the which vauge reference to a BCUK thread you prefer.
I agree Nagual, having now looked into this method it doesn't seem to be of any real use out in the field --- Bravo4, not boring at all, thanks info, i didn't know about this and learning what works and what doesn't is never a waste, i agree with the sin of losing a map and have never lost one myself however i mentioned it only as an example to highlight the fact that if you have a map you can find out the distance anyway from map and if you don't have a map therefore no known knowledge of heights then method is unusable anyway, therefore method doesn't serve any useful purpose, The only way to decipher what you hear and read about is to put it into practice and find out for yourself, thanks for your time fellas much appreciated.
I think it all becomes more clear when you consider it's original use...
I assume the "soldiers" were practicing "escape and evasion", where maps might not be available, and "Anything" would be more useful than nothing! but they'd have known roughly which direction to head.
It may for instance help an escaped WW2 POW figure out how close he can get to safety given this scenario:
there are 2 escape routes only, down each route are your troops but which can you reach first? a quick calculation could save your life.
(or......you'd make a fire, shout, flash a mirror, etc etc , I know I know, I'm trying to figure out who would use it too!)
I guess they had to use anything they had to hand (oops pun!) I've just been looking at a book in which WW2 POW's managed to make a wooden sewing machine to make fake German uniforms! different times different needs!
I assume the "soldiers" were practicing "escape and evasion", where maps might not be available, and "Anything" would be more useful than nothing! but they'd have known roughly which direction to head.
It may for instance help an escaped WW2 POW figure out how close he can get to safety given this scenario:
there are 2 escape routes only, down each route are your troops but which can you reach first? a quick calculation could save your life.
(or......you'd make a fire, shout, flash a mirror, etc etc , I know I know, I'm trying to figure out who would use it too!)
I guess they had to use anything they had to hand (oops pun!) I've just been looking at a book in which WW2 POW's managed to make a wooden sewing machine to make fake German uniforms! different times different needs!
