Big cliff height measurment????

[simon]

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

[h00ktern]

<center><font size="1" color="#ff0000">LAST EDITED ON Nov-18-99 AT 06:01&nbsp;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:
http://home.earthlink.net/~h00ktern/images/solut.jpg
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

[imported_mknutson]

For future reference, you can find it in the "tools" section. I have used this with a laser range finder and is very helpful!

[simon]

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

[h00ktern]

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.

[460]

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).

[guest]

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 !

[guest]

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.

[guest]

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 !

[guest]

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.

[guest]

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.

[guest]

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

[guest]

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

[guest]

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

[guest]

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.

[guest]

thanks for your concern,the whole thing isnt as gun ho and spur of the moment as I have have made out,when I ask a question I ask it as if I know nothing on the subject,that way you get a broader response and you get to reconfirm your own knowledge.
I understand the base communities concern and I am not going to lie and say this trip will not be dangerous,and possibly someone could die because of relatavly stepping into the unknown but this expedition has been two years in planning,using nothing but the best gear and the top climbers in the world.The people involved have a heavy training schedule for the year and the end result is basically edited by the people involved(one of whom is a film maker)
Additional to this,the main people involved have taken out insurance policies so that if there is a death the film will never see the light of day and the people who have put up the big bucks will get there money back.
This isnt a sunday afternoon sitting at the pub and saying `lets do this
Dont be concerned and please dont compare me to Rooney.
Thanks for the feedback though.
Simon Golding
Ps What height is this cliff your talking about and have you used a suit off it,would like to hear any info you have.

[guest]

>Dont be concerned and please dont compare
>me to Rooney.

We wouldn't dream of comparing you to Jason Rooney. Rooney had more experience than you and from what we've seen he had far more natural ability and talent as well.

If somebody had the same number of skydives as you have BASE jumps and they wanted to do a high altitude skydive would you recommend or encourage it?

Perhaps you should concentrate on advancing your BASE jump skills and numbers before attempting anything difficult. I'd recommend at least 500 BASE jumps off around 100 different objects as a good start.

Ego desire for fame limited experience = high chance of fatality.
Add high altitude and a minor gear problem to the equation and death is pretty likely.

Just because Glen lived through BASE climb with his 11 BASE jumps doesn't mean you will survive a similar experience.

Please don't let your desire for fame and recognition distract you from realistically evaluating your current skill level.

[guest]

2 things that I really hate(politics and bitching)especially in such a free minded sport full of very open minded people willing to push barriers and explore their own capabilities.Fortunatly you are the minority.
I am at a loss at where this attack has come from and why,what have I possibly done to you to warrant this?Have I jumped with you,did I crack onto your mother,What?Do you know how many objects I have jumped(I didn`t think so).
I have basically spent my whole adult life in the air,went solo in helicopters from 7 hours(is that enough) and went on within 6 months and flew commercially.Started skydiving and became an instructor within 1 year,Is that enough time,did I have enough jumps,you should tell me!Alot of people would say no until they found out the facts ,My students seem to be happy.
I was taught to BASE 3 years ago by someone who didn`t have hundreds,but did a brilliant job.
One thing I never do ,even now after thousands of
jumps is to think I am above people and stop listening to advice and stop learning,and that is exactly what I was trying to do with a technical question of how to measure a wall on a giant cliff.Should I know this after Blue Mountains?harbour bridge?Norway?
How often have you had to do this?Are you the person that should be doing this?Who is the world expert on jumping in thin air,It sounds like you!
As for ego and desire for fame,these are tall calls from someone who I do not know,If I had a large ego,I wouldn`t be asking for advice on the board and from friends involved in BASE.As for desire for fame,I am meerly doing as I want,something most people strive for.
You sound like you have a few hundred Base jumps but sadly you have a clouded mind,You sound as if you dont make a mistake,you sound almost perfect.
How do you evaluate someone on their ability?I have seen people with 200 jumps kick the arse of others with 1000,but they may not be able to spot.
Also I think the current world altitude record holder,Kittinger had 30 skydives when he jumped from 103000ft,mabye you should give him a call and tell him he is a fool?
I really do not know where you are coming from with this attack,I have no grevances with any jumpers.If you were generally concerned you would email me direct instead of public slandering,it is sad to see such bitching on a great information sharing board,there is alot of people here who have a lot of knowledge to share,you do not sound like one of them.
I am here for information,not to hear that I cannot base jump,I desire to be famous,have a big ego and I should not chase dreams.
BITCH SLAP YOURSELF because your a bitch!
Regards
SIMON GOLDING(Yes thats my real name)

[guest]

It seems like Concerned and others are concerned! It sounds strange that in a so big expedition there is no people able to answer all the questions you ask on the baseboard.

However, you do what you want and I assume you know what you are doing.

Just a few words to answer to your altitude problem (I'll compare sea level and 20000ft altitude behaviour):

- Air density is about half its value at sea level (typically 0.53)
- Terminal velocity will be multiplied by 1.39
- The time (to reach 97% of the terminal velocity) will be multiplied by 1.37
- The height (to reach 97% of the terminal velocity) will be multiplied by 1.94

Your will have the same feeling and control at terminal velocity but as it takes a longer time to reach this speed, a given time after the exit will provide you less control.

Using a wingsuit depends on what you want. You will still gain regarding time, speed, and height but differently than at sea level:
- The benefit regarding time (for a given height) is about 25% less than at sea level.
- The benefit regarding speed is about 20% greater than at sea level.
- The benefit regarding height (for a given speed) is about 20% greater than at sea level.

On an aerodynamic point of view, the similarity of the openning yields a greater time and height (same proportions than previous). The deceleration will be the same. But on a "mechanical" point of view, a greater opening time leads to a fuzzy opening. The vertical speed during landing depends on the aerodynamical characteristics of your canopy but will surely be greater.

If you want, I can provide you "formula's" if you or one of your guys is able to use it.

[guest]

Yes it does seem some people are concerned,but then again it seems people are concerned about alot of things other people are doing on this board!
No doubt there will be people with alot of knowledge on this trip,but unfortunatly they are not sitting around with me in my lounge rooom every night,they are in all corners of the globe ,we meet up for some high altitude training in a couple of months,it all goes back to trying to get as much info as possible.
Your information is excellent,I am not very mathimatically minded but I am willing to learn more.I would really like to hear of these formulas and also learn how these effects change as you go higher to say 25000ft.
On a final note for everyone reading,nobody here is perfect,we are all learning.I see things happen with more experienced and less experienced people than me go wrong and right,and I think to myself that I would have done things differently,but I dont judge them for it and certainly do not try and publically humiliate them for it.At least they are having a go.Give people respect and dont treat them like children.
Thanks again for all information supplied.
Simon

[guest]

You speak too much guy. Don't waste your time to justify yourself, ask your question and concentrate on what you need. Forget all other stuff. I don't care if you're able or not for the job. You do what you want. It's you to decide. Read only answers that give you objective informations to help you to decide. The BaseBoard is full of boring polemical messages.

Just a few equations:
The dynamic equation is a non linear differential equation:
dv/dt=-k.v**2 g
with
k=(r.S.cz)/(2.m)
**="power of"
r=volumic mass of air
S=aerodynamic surface
cz=vertical aerodynamic coefficient
m=mass
g=gravity acceleration

The solution of this equation is (velocity):
v(t)=sqrt(g/k).tanh(sqrt(k.g).t)
with
sqrt="square root"
tanh="hyperbolic tangent"

Terminal velocity: V=sqrt(g/k)

The integration is (altitude):
z(t)=1/k.ln(exp(1 sqrt(k.g).t)**2)/2)-sqrt(g/k).t
ln="logarithm"
exp="exponential"

r=:
- 1.225kg/m3 at sea level
- 1.057kg/m3 at 5000ft
- 0.653kg/m3 at 20000ft
- 0.551kg/m3 at 25000ft

g=9.81m/s2

The product S.cx is between 0.4->0.6, and can be greater with a wingsuit. S increase proportionally to the wing surface. cz variation depends on the wing shape but obviously slightly increase (ask the manufacturers!).

That's all for the scope of the BaseBoard.

If you need more details/informations, the BaseBoard is not the right place nor the right media. I'll email you if you request it.

[guest]

I made a mistake in the z(t) formula (text editor is not the right tool for formula writing). The altitude formula is:
z(t)=1/k.ln((1 (exp(sqrt(k.g).t))**2)/2)-sqrt(g/k).t

If you take k=0.00378 (approximately) (unit is 1/m), this formula gives the same results you can find in the Tools section of the BaseBoard.

[guest]

people like you piss off the realist's of this beautiful planet- stop bitching like a bitch-you probably are!!!!!!!!!!
simon's experience is not the question so ##### off and get yourself a gun, be shaw and put a bullet in it dickhead and have the balls to put a name to your #####
simon jump the cliff and look in free fall, it works for me!!!!!!!!!!
doesn't matter mate if your going to hit something you deploy your ???????????????????????
go hard and take chances, it's that how the sport began!!!!!!!!!!!!!!!!!!!!!!

[web]

i think i can do it with a 12-channel GPS, 100m clear 6mm teflon hose, a bottle or two of red wine, a rock and string, and a marine sextant to measure the angle between horizontal and line-of-sight to the exit point. know the Lat/Long of exit and observation points, and the rest is just geometry. anyone care to help develop this? i need someone to hold the other end of the hose.