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I'm currently interested in a cliff with a big talus and wondering how to calculate the exact height to the landing area using a rangefinder from there.
Thank you in advance.

Basic trigonometry will give you answers. See attached picture.

height (blue) = red (rangefinder) * sin (blue angle)
height (blue) = red (rangefinder) * cos (red angle)

Angle can be measured to couple degrees or so using a plain plastic protractor.

Hope it helps

Can you re-explain that? I've learned this once before when I started trig, but that doesn't make any sense to me. Are you saying you can figure the height by taking only one range finder reading? That's what it seems like? height = where your at to top * sin? also height = where your at to bottom of cliff * cos?

 
>>Sine Cosine, Cosine Sine! 3.14159!
Captain's log, Stardate 31085.05:
Rollover's are neato!
-Jason

Buy an alti watch, go to the landing area set it to zero then make your way up to the exit point. That tends to do the trick, give or take 20feet or so.

This way, you get the added bonus of checking out the landing area and the exit point first, and whilst at the exit point you can get a very accurate reading of height to impact using your laser, something you absolutely cannot do using a laser from the landing area.

http://en.wikipedia.org/.../Pythagorean_theorem

Coco

why?
just eyeball it.

yes, I'm serious. isn't that what we do during the jump? (both before and after opening...)

if you can't tell, jump conservatively. if the site looks marginal for a conservative jump, DO NOT jump.

create an experience base with the site. then build on YOUR experience. height is just one variable. skill level, equipment, density altitude, wind patterns, etc. constitute many other valid variables. why worry so much on calculating only 1 variable?

if it's so marginal you feel you need a precise measurement, DO NOT jump. it IS that simple. why insist on complicating things?

The way I did it at Kjerag was to mark the exit point on my GPS, Go in the boat with my angleometer and cruise out until i had a 45deg angle on the exit point to give me the height. and then go to a 45deg for the talus or in this case, ledge, then subtract.
Hope this helps.
I can give you more info as to my glide angle meter if you wish. PM me.
take care,
space

Attached are two pictures that hopefully explain better

Can you explain that more? You range finder C1 and C2, but how do you get B1 and B2? Maybe I'm way off of what you were explaining.

Awesome thank you. I'm saving that image.

My pic from my last post didn't work so here it is again.
[img=http://img158.imageshack.us/img158/5960/picas9.jpg]

looks like someone turned off the image bbc code.
http://img158.imageshack.us/img158/5960/picas9.jpg

Careful with the setup, particularly the angle measurement. Errors will accumulate quickly.

yah i was thinking you'd need to fix a protractor with an adjustable laser pointer on it to a level. That and binoculars. it'd probably have to be a badass laser pointer too.

Someone should build a combo laser rangefinder/sextant unit. That would be pretty cool...

cool but impractical...

and talk about device dependent... (oops, I can't evaluate the site, my batteries are dead. guess we must go home...)

I know of one alternate BD site that I've heard several different heights. somewhere between 220-240 ft. that represents over 8% error! it's a bridge! all it takes is a rangefinder pointed straight down, but we can't derive a consistent figure... guess how much it would vary if we had to measure angles as well? (oh, but it is a laser! it is accurate! - yeah, right...)

last year, an intelligent jumper did an aggressive jump there based on these numbers. he got busted up.

how the data gets interpreted (including awareness of error) is far more important than the data itself.

I feel that statement is inherently flawed...

uh, I see your point...

maybe replacing "intelligent" with "otherwise intelligent" would be better?

I didn't get busted up because of my opinion of the height. I got busted up because of the altitude lost in a rear riser turn avoiding the pillar I would have otherwise smashed into. And a few of the luck factors that didn't play into my favor.

After months of reflection, the other factor that played a big part in my injury was trying to get to the only landing area I had evaluated rather than having suitable alternates in the event of whatever might happen.

I think another isuue with this object and the perceieved differences in height have to do with the landing area. My 240' measurement, with a laser, was to impact. In the possible landing area there is a hill, train tracks, a river, a path, ditches on the side of the path, etc. With all these things considered it is a pretty challenging object to FF and have to deal with heading performance and deployment hesitations.

BTW, I will be headed to potatoe land next week for my first jumps back from the injury. I think my biggest challenge will be hiking out. I still have quite a bit of pain.

Tony

Now THAT statement I agree with !!have to deal with heading performance and deployment hesitations.

as you so clearly state, there is far more to site evaluation than simply knowing the altitude. I'm hoping others can learn from your unfortunate experience.

I have yet to do anything other than a static line or PCA from the same object. I'm not comfortable opening lower, yet. my experience there is guiding me more than a range finder...

good luck in potato land (or potatoe if you from the Dan Quayle school of spelling...).

Hey Tony

I'm bringing this post back cause it brings me back to a story I heard in Base Camp w/ Johnny Utah.


You might find this article usefull. The 1st story at the end of the article relates to yours b/c it was the same object




http://www.johnnyutah.com/risersortoggles.html

Joe

That is definitely one of the on-going questions in my head to this day. Risers or toggles??? My instinct is risers turn faster and I don't have a good feeling for altitude loss, this being only my second rear riser avoidance turn. I was surprised with the altitude loss the first time also.

Something good for my project this next week.

Tom Aiello is working on a post as we speak where he's going to point out that "faster" is a vague concept in this context. What are you trying to optimize? The time it takes to turn the canopy? The distance traveled horizontally? The altitude lost?

I would say the first one (which is commonly implied when one speaks of "faster") is of no importance. The second two are crucial. If there was a way I could turn my canopy with zero forward speed and not losing any altitude, except it would take thirty minutes; I would obviously prefer that.

Now just looking at the time component, I would argue that I can turn faster with toggles than I can with risers. That says nothing about the two more important factors. That said, I think even those are more optimized with toggles.

Although then again, it's a tough call. If you don't release your toggles the right way, you could create a surge increasing your forward speed.

Once you include the time it takes to reach up for toggles and the potential to miss one, the debate becomes even more complicated.

And despite all that, this discussion has never been very hard for me. I go for risers. It's simple, foolproof, and will work for many highly enjoyable objects. And those objects where a decision to use toggles may be needed? I try not to jump those.

Case in point, that particular bridge you had your injury on; I jumped it three times the year before. One PCA, one static-line, and one TARD.

No freefalls.

Why not? Because it wouldn't give me enough time. And lack of time turns simple questions (like risers versus toggles) into complicated answers. And in this sport, complexity equals injury.


This is where CRW shines.

...in a real life emergency situation. Right?

Gotta love Perrine floaters.

Real life, I'd better hurry up and get this boat turned around situations.

Are you in Twin? I'm headed up tomorrow for a week.

Skydiving I find if I get an offheading risers get me turned around much quicker, time wise. As for altitude loss and distance traveled, I have no idea.

Regarding my incident, the pillar was coming at me quite rapidly, especially when you consider that I didn't think there was any way for me to reach it. Now I know. So next week it's time to tune my DBS and do some riser vs. toggle testing...

What is interesting to me is, why did you have to get hurt first before you realized this?

Don't get me wrong, I'm not taking a stab at you. I've done plenty of stupid things and could have prepared better to avoid those cases where I got myself in trouble.

Information is readily available to everybody. Yet so many of us ignore it until we learn lessons on our own. Understanding the mechanics of our choice to ignore this information may improve the guidance we offer to future jumpers.

I was taught to pull both risers or toggles (depending in wether or not you are a toggle or riser person) down which will stop the canopy. thereafter you snap one arm down and the other one up (depending on which way you want to turn).

When executing this you will eliminate forward drive. Therefore it is very possible!

I am a riser guy at the moment but I am training to be on toggles primarily. Once you are fast enough and confident on your toggles...I believe they are the better option!


Joe

Are you speaking from experience? Can you share any GPS data or video of this?

Thanks!

Almost every time heading needs to be corrected, I have done the maneuver I described.

Furthermore...Myself and some friends have seen it done as well. Video is available.

Of course you may have some drive at first in between the time you grab your toggles or risers. I guess if we are gonna be picky, then forward drive isn't fully eliminated....if you're too slow!

FINAL NOTE: IF YOU ARE FAST ENOUGH ON YOUR TOGGLES AND ARE DIALED IN ....FORWARD DRIVE WILL NOT EXIST ANYMORE THEN IF YOU WERE USING YOUR RISERS!


Videos on my mentors site probably show it and I have some of my jumps on camera which show it as well.

take care

Joe

I emailed Johhny Utah and asked him to put video of what he was doing during BASE Camp. These videos demonstrate how the use of toggles can minimize forward movement during and after opening while doing a heading correction.

These videos also show how quickly the canopy can be turned with minimal altitude loss with the use of toggles.

The titles of the 2 videos are:
"Toggle Heading Correction During Opening"
"Toggle Training"

http://www.johnnyutah.com/videolibrary.html

Joe

Isn't that what a properly tuned DBS is for?