Howdy goons
Any of you guys have any idea`s of measuring walls of big cliffs fairly accurately from the base.
Have rough estimations from climbers but there is discrepencies of height,from 1500 to 3000ft,climbers were at altitude and slightly off there heads.
The mountain is over 20000ft and a bit of a trek to do a rock drop.
It`s not Trango and it has not been jumped before.
Any idea`s,lasers ,surveying equip , thumb method, psychic monks??
SIMON
<center><font size="1" color="#ff0000">LAST EDITED ON Nov-18-99 AT 06:01 PM (EST)</font></center>
LAST EDITED ON Nov-18-99 AT 08:02 AM (EST)
LAST EDITED ON Nov-18-99 AT 07:53 AM (EST)
One solution is on this site: Technical/Tools/Pythagorean Theorem
Pythagoras' theorem is available for this purpose, however, in your specific situation, I doubt you will have access to the equipment neccesary to measure such great distances. This based upon a calculation from zero elevation to 20,000 feet.
For clarity, using smaller distances:
As you can see, accurately measuring Side C, given the height of Side A (at some 20,000 feet,) involves use of equipment which is not generally available to we financially insignificant beings
If your scenario is markedly different than what is shown above, clarify some particulars (limited to points relative to your intended exit point) and we'll see if there is a practical solution.
Sorry Mick - had to get solut.jpg on here somehow
For future reference, you can find it in the "tools" section. I have used this with a laser range finder and is very helpful!
thanks for the help,I will paint the senario a little more.The base of the vertical wall is somewhere around 20 000ft ,so I cannot be on the level with a 90deg at the base of the wall,if I was on this level,I may as well keep climbing and do a drop test.
My understanding is if you have the measurments of 2 sides,you can work out the 3rd side with your formula,or if you have the measurement of 1 side and 1 angle(not the 90deg angle)you can work it out with another formula.
So does this mean I need a laser rangefinder to do the job(do they work accurately at that distance?)
Do you have any other thoughts or idea`s,might have to get a surveyer or someone hey??
SIMON
Assuming your standing at the base of the mountain (the shortest distance for a measurement,) that would still leave you measuring a minimum distance of just over 6,666 yards (3.78 miles!) Not likely with any "affordable" rangefinder.
Regarding the "1 side and 1 angle" formula, I'm at a loss. To derive a meaningful answer, not in algebraic form, requires one other known value, either a side, or angle.
If you know one side, and one angle, what is stopping you from ascertaining one other side or angle?
With that, you can solve your problem.
it's been a long time so i'll have to rederive the formula to give an estimate of the height of something. it's based on how the size of the object changes from its appearance when you get closer or farther away. in other words, you don't need to know how far away you are from the base - just how the apparent size changes when you move, say, 30 feet closer. You see, the "apparent" size of something is inversely proportional to the distance from you. i'll figure it out and post it in a while (could be a few days to a couple weeks).
Sorry for my english, I'm french !
There is an easy way if you can evaluate a distance.
Move away from the vertical of the jump point on the ground. When the jump point is at 45 °, stop there. 45 ° is easy to evaluate because it is the middle between the vertical and the horizontal. Then the height of the object is the distance from the bottom of the object. See the image below :
http://www.multimania.com/cadene/45.jpg
Be sure to apply a margin in your evaluation for safety !
Another way a little bit difficult if you can't access the bottom of the object (fences, trees ...). You will have to evaluate a distance and 2 angles. And you will have to calculate the tangent of these angles i.e. have a calculator (pocket calculators do it now), see the image below :
http://www.multimania.com/cadene/tan.jpg
If you can't calculate, with an "a" angle of 60° and a "b" angle of 30° the height "H" will be 86 percent of the lenght "L"
Be sure to apply a margin in your evaluation for safety !
If you can't reach the bottom of the object (which is usually the case) these are two of the methods I use for height measurment when I have no map of the site.
1- Angles method:
First you need to be able to measure angles between horizontal and a pointed object. For this, you can use an air level (the long ones for brickwork) and a 2/3ft wooden rod. Keep the air level horizontal, points the object with the wooden rod (top of the cliff for example) and measure the angle between the two devices. If it is well done, you can acheive an accuracy of 2% or 3%.
Next there is a distance to measure between two points. For this, there is a lot of means (car or bike counter, specialized devices...).
I will use some notations:
- H = point on the top of the cliff (exit).
- L = lowest point of the wall.
- h = the height of the wall (distance between L and H)
- M = point of the first measurements
- N = point of the second measurements
- d = horizontal distance between M and N
You have to find two measurement points. The first one (M) is ideally at a distance from the cliff approximately equal to the total height of the cliff. The second one (N) is ideally twice this distance (it's approximative, not critical).
At point M, measure two angles a1 and a2. a1 is the angle between the line ML (bottom of the wall) and the horizontal. a2 is the angle between the line MH (top of the wall) and the horizontal.
At point N, measure two angles b1 and b2. b1 is the angle between the line NL (bottom of the wall) and the horizontal. b2 is the angle between the line NH (top of the wall) and the horizontal.
Now measure the HORIZONTAL distance d between M and N.
The calculation is:
-> A = tan(a2)-tan(a1)
-> B = tan(b2)-tan(b1)
--> h = (d*A*B) / (A-B)
It seems difficult but not very much into practice. The advantage is that measurement points (M and N) can be at any altitude one to the other or with regard to the cliff (be carefull to use negative angles if M or N is higher than L or H).
The only restiction is that H,L,M,N must be in a same vertical plane. If not, the formula is still valid but the distance "d" must be (distance between N and cliff)-(distance between M and cliff).
Keep in mind that "d" is a horizontal distance and not a direct (straight line) distance (if there is a few altitude difference, direct distance is a good approximation).
If the angle measure is 2% accurate and the distance measure is 3% the result will be about 10% accurate.
2- Binoculars method:
This method is easier to implement than the first one.
If you can get a binocular with a scaled reticle or cross wires it is the best but very expensive. But you can do about the same without reticle. Use a x10 binocular (x8 or x12 is ok).
You need first to calibrate the device. For this, chose an object of which you know the height (or the width). Measure the distance of observation where the object full fill the field of vision of the binocular. The ratio of this distance to the object size gives you the exact zoom factor.
You now can use this factor to measure the height of any object if you now the distance between you and this object. If you can't know this distance, there is another solution: measure the distance between the point where the object full fill the field of vision and the point where the object half fill the field of vision. This distance divided by the zoom factor gives you the size of the object.
With a reticule, it's easier to use part of the field of vision (not only full or half) given more flexibility to this method. The calculation is only a proportional rule.
If you can't get far enought from the object, you can process by steps along the object.
All these considerations assuming the axis of the vision is approximately perpendicular to the size (height) of the object to measure and with at least a x8 device (to allow the approximations inherent to the calculation). If not (especially if you do the process by step) don't forget to correct the result using the Pythagorean's theorem.
There are many other methods but all depends on the tool you want to use and especially what kind of measure and where (regarding the position of the object) you can do it.
If tou know the exact distance you are standing from the base of the wall, then you can take the angle with a simple sighting devise like a protractor and compute the height of the wall with a fair degree of accuracy. Math man !
The next methode is with the use of a GOOD 6 or 12 channel GPS. With this, you should be able to get within 100ft. if you can aquire at least 5 or more channels with good signal strengths at the same time. If possible, take several readings over two days every two hours, eliminate the outside results and average the remaining results to increase accuracy. Call DOD and/or FAA at time of tests and ask about area degredation. Ask if it's category II equivelent after telling them it is for a non-aviation use.
If it's that big, just jump it and pull before you hit the ground. However, the other day in a deep, narrow canyon in a National Park in CO, I got a little carried away and hummed it a little low. Had to land on a very tiny speck of a sand bar. If you're doing it over sand or snow, be carefull. If you are still wanting more info, take me and I'll go first for your wind drift dummie.
Thanks for the info guys,much appreciated
I will find out how high this wall is yet,checking it out very shortly
Fox,it is over ice and snow and unfortunatly just the climb fee alone is around $10 000us per climber.
Any other idea`s would be great,the more the better.
Thanks again
Simon Golding
Just out of curiosity, will your rate of descent be faster....as when you skydive at higher altitudes? How would you calcuater that?
Peace.
Out.
B
Yes,but I have no idea on how to calculate this,I guess it would have to do with height ,weight,temperature and probably a few other things I have never thought of.
It is just one of the problems that we have to overcome,others are hypoxia and landing.What are the parachutes going to open like,what will a wingsuit fly like off something at altitude?,not to forget all the climbing difficulties.
You guys know any more formula`s?
Simon
media ego limited experience = death
Simon
All I can say is, Good Luck. It looks like you will need it. This is not a personal attack but you and all the flamers out there can take this reply any way you want. Your obvious lack of knowledge in height determination, the affect altitude has on freefall stability/speeds/...., wingsuits, high altitude mountaineering, etc could prove to be your downfall.
Sounds like you have a big adventure planned. You probably have the media involved as well. My advice is to get someone who knows what they are doing to be involved in the project. If you bounce because of your inexperience with wing suits, altitude, BASE, etc it will further damage the sport and will undermine any positive reputation you have in the sport (Jay Rooney).
High altitudes mean hard landings, mushy (i.e not solid and quick) openings, greater height consumed during openings, greater descent rate, reduced control in freefall, etc. add to that the affect altitude sickness will have on your thinking and problem solving abilities as well as reaction times and you could be in a bit of trouble.
Flying wing suits at 20000 feet reduces their performance considerably too. They need to be flown slightly differently to normal sea level (<10000 feet) jumps.
There is a big cliff here in Nth America that has taught us a lot about altitude jumps.
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