Basejumper.com - archive

Hey everyone, There is an A near my house and I was just wondering how I would know it was jumpable?
How can I determine how tall it is?

You could use an altimeter, since you must go up there in order to jump it anyway. I've done the fly by in aircraft, that works...

Climb to the top. The rungs are 12" apart. Take Ranger beads.

Post a pic, and we'll decide if it jumpable and what delay to do

look in your base jumper handbook.

buy a laser. IMHO anyone opening shit up should have one. I keep mine in my car.

And now you know where to pick one up...

I can't help you on the "Is it jumpable" part.

As far as the height is concerned, go to your local airport, and buy an FAA Sectional Chart for your area.
The tower and it's height above the ground will be depicted.

If there is more than one tower in a small area, it is possible that only the highest tower height of the group will be stated.

BASE359

the easiest thing in the world is breaking into a frame-less door subaru. I have locked my keys in outback countless times. I dont keep a spare key outside, I keep a spare COAT HANGER.

ive found that they generally over estimate the tower height on the sectionals, im assuming to give a pilot a bit of a buffer in an oh-shit situation.

there are better ways to determine tower height down to the exact foot.
all easily found with just a bit of research.

but anyone asking "how do i know if its jumpable" on the internet, obviously dosent have the site evaluation skills needed to be basejumping.

end of dorkzone rant. -b

Suuntos work well also. Start climbing with a 42", when you get to 350', and the winds are good, JUMP! If there is still tower above you, keep climbing for a little bit.

Get the FCC tower # from the fence, and look on the FCC database...

But, since you are asking how high a random tower is, without a pic, from strangers on the internet, you might want to take a second to think your plan through. Good luck!

The height of towers listed on FAA sectional charts is not estimated.
It is the actual 'reported' TOTAL height of the structure above the ground, not just jumpable height.

BASE359

You could always jump off of it...if you live it's probably jumpable. If you don't, we'll all know that it isn't.

nah...

I call that the Darwin altimeter...

Or you could just stay home and do an ASR search.

Wait for a sunny day. Get a yardstick and a tape measure. Measure the shadow the antenna casts. Measure the shadow a yardstick casts.

Bust out a little Pythagorean theorem... you're set. You know the height.

Or... get a laser rangefinder.

And do it at night, so not to be noticed...

There's not really much need for that. If anyone asks what you're doing, tell them you're doing a math project where you have to estimate the size of objects by using proportions...

I think even most police officers would buy that.

If you're trespassing, be polite and apologize. If you explain what you're doing as part of a class you're taking at the local community college, you're probably okay.

I've been on bridges in the daytime and used the "engineering student" excuse.

Just have your story ready ahead of time.

Absolutely, the best camo is to become part of your surroundings, even if it means standing out.

Our first A was television broadcasting, and had an occupied building, but with no windows. After climbing and playing on it for awhile, we went to the door and knocked until some guy answered, and ended up with a tour of the facilities. Much gratifying...

A lot of towers are painted in sections of red and white. Does anyone know of regulations describing how long each section is supposed to be? The it would be simply a matter of counting the red/white stripes.

I've come across too much variance to rely on counting the sections. I've seen them as short as 50', and as long as a couple hundred. I'm not sure if there is a regulation, but if there is, it's either very loose, or very loosely enforced.

very easy. look at it, and where the tower sections are joined together (flanges) count the number of sections. most towers are usually 20ft sections. if it's bigger it could be 30ft. the colors don't mean shit.

if you can walk up to the base, you should be able to figure out how big the main sections are just by standing next to it.

also must rungs i've run across on climbing ladders (and pegs for that matter) have a 15" spacing.

 
For me counting the number of lights has been better than using the painted sections. Usually 3 means jumpable, 4 means very jumpable.

that might work once in a while... but that's a very bad idea.

in fact, i have a guyed tower near my house with 4 sets of red blinking lights that is less than 150ft tall.

This is without a doubt the easiest way. And any laser will do. Your local Wal-Mart will carry diode pen lasers for about $20.

You'll also need a really accurate stopwatch.

Then, simply climb to the top of the antenna, pick your exit, and shine the laser directly down at the ground, being sure to start your stopwatch the instant you flip on the laser.

Then wait until you see the laser's beam hit the ground. The instant this happens, halt the stopwatch! Be sure to shut the stopwatch off instantly, or you'll calculate a higher altitude than desired, which could cause you to take a dangerously large delay.

Then, simply divide the reading on the stopwatch (in seconds) by two and multiply it by 299702547.23582925122463261021693. The result is your exact height in meters. I'll leave the conversion to feet as an exercise for the reader.

* Be sure to start and stop timing immediately. Even an extra tenth of a second on the stopwatch would result in an extra 14 985 km in measured height, which could cause you to pound in from an excessive delay.

so hilarious

Get a roll of mason string or twine. Tie a bolt onto the end. Mark the string in 50' increments with sharpie. Climb structure to desired exit point. Place self on tailwind side of structure and roll out string until bolt touches ground. Tie a knot in string at exit point. Measure distance from knot to bolt. Count correctly. Let me know if this works.

You're going to get somebody killed. Jerk. It's been defined at 299792458 exactly since 1983.

You forget that light travels slightly slower in air. About .03% slower.

Ooh. Touché.

All the humorous answers aside, I just came up with an idea how to measure the height of any object without the need to even come close to it, using just a digital camera.

Take a picture of the object at some distance from it (far enough that the lens' field is "flat" (i.e. angular distortion-free)). Leave something of known length (e.g. your friend - pretend you're just taking a tourist snapshot) where you took the first picture, walk some distance straight away from the object and without changing the focal length take the second picture.

Open the pics on computer and measure the three lengths in pixels - the height of the antenna P1 in the first and P2 in the second picture, and height of your friend P3 in the second picture.

These pixel counts are proportional to tangent of the angular measurements. If the unknown height of the object is H and you were at unknown distance X from it when you took the first picture,

P1 = K*H/X

where K is some coefficient depending on focal length, camera's sensor size and pixel count.

For the second picture, you walked some unknown distance L, so

P2 = K*H/(X+L)

If your friend's height is h, then

P3 = K*h/L

We have 3 equations with 4 unknowns: K, L, X, H. Fortunately, K cancels out when we derive H:

H = h*P1*P2/P3/(P1-P2)

Very simple, quite accurate and does not raise any suspicion.

I'll test this method with Empire State Building, let's see how close I will come with the correct number. Anyone to try this method, too?

Yes, I appreciate your concern. I was just wondering because there are no cliffs or bridges that I know are jumpable near me. I've seen these towers countless times so I just wanted to see if anyone could help me determine the height. But thank you everyone for your help.

 
This reminds me the following story of several good ideas how to measure the height of a building. all of them are valid of course.

http://www.mentors.ca/bohr.html

(for the irony - the link is from 'mentors' web site)

A picture is worth a thousand words sweet altitude.

1% accuracy... not bad for two quick snapshots!

"The most common form of laser range-finder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the object and measuring the time taken by the pulse to be reflected off the target and returned to the sender."

http://en.wikipedia.org/wiki/Laser_rangefinder

but... how can they make the device click the stopwatch so fast??

They have really tiny bits of metal suspended above really tiny bits of glass, with silicon all around. Then, funky electron stuff happens.

Actually, a lot of processors will have a special peripheral for very fast and accurate timing. It just happens to be called a PCA.

so theres not actually a real stopwatch in there? laaaaame. i like noamk's way(s) better.

100 years ago crazy Russian scientist Lebedev discovered that light has pressure. The reflected beam knocks off a tiny rocker switch and stops the clock.

http://en.wikipedia.org/wiki/Light_pressure

Very small, highly-trained ninjas.

ohhh ok now it all comes together..

thanks

This usually seems to be accurate if the antenna has working alternating solid and flashing red lights.
http://www.vertical-visions.com/antennas.php

The regualtions about marking antennas are probably in here somewhere:
http://ecfr.gpoaccess.gov/.../47cfr17_main_02.tpl

The ASR seems to me to be more accurate and up to date than an aviation chart, but it doesn't seem to list all antennas, and it's not perfect.
http://wireless2.fcc.gov/...gistrationSearch.jsp

One source for online aviation charts.
http://www.flyagogo.net/

Personally, I prefer the pull when you get scared method. Take a short enough delay the first time you huck something. If you didn't get scared enough, pull a little lower next time. If you get too scared or busted up, tell your buddies not to hum it so low.

According to this website it's 108.8 meters or about 350ft. Sorry no picture I've been busy, I'll try and get one though, there are actually three towers. So does this mean this is the tallest?

Be smart, get two as described above.

You can't use the color bands on a tower to figure the height towers, the bands are 1/7th of the height of the tower if under 700' (I believe thats the cut off) then they add more bands above that at set limits aways starting red and ending red. 1/9th, 1/11th, 1/13th, ect... no more than 100' each.

What I'm saying is the bands on a 350' tower would be around 50' each while on a 250' tower they would be around 36' or so and a 500' tower would be around 72' each, you follow?.

Also all towers over 200' are lit day and night or painted if not lit during the day, only if near an airport or other type aircraft area they might be lit while less than 200'.

Link below covers painting and lighting per FAA, tower marking is on pg14 in PDF file.

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/b993dcdfc37fcdc486257251005c4e21/$FILE/AC70_7460_1K.pdf


Here's how I figure it's jumpable or not...

1. Tower is out near nothing and lit or painted, S/L at worst from 200'

2. I look at it scratching my head, then the tower is too low.

3. What really do is get out of my truck with a clipboard in one hand and a laser range finder in the other. Walk up the the gate and write down the FAA tower number then hit it with the laser and leave and look it up later.

It also helps to have a truck that says Motorola all over it too, no one questions it.