Basejumper.com - archive

My real question is:
Is there anyone who has any general beta on how long guy wires must be on an A of a given height? I'm trying to estimate heights on G. Earth and I can measure the distance of the guy wires from the tower, but without that knowledge It doesn't do me any good. I'm sure that they must be at least the height of the tower, probably more, but anyone who knows a bit more on the subject your dropping of said knowledge on my ignorant ass would be welcomed and appreciated.
cheers,
pope

measure the distance from the base of the A to where the wires are anchored.

A squared plus B squared equals C squared

you probably know this, but there is no 'set' angle-distance formula for different towers.

I can tell you that I have measured a fair amount of tower foundation to guy anchors very accurately, and fartherst anchors on 1300-2000 A's are about 70% towers height.

also google earth warps sat photographs (even for seemingly level terrain) to fit strange satelite view-angle photographs onto topographical data.

Can you post a crop?

I'm a shitty mathematician, but I do know that basic trig... Only that's not possible with what I'm asking, since I only have one part of that equation in my situation. Thanks though.

I didn't know about the sat photo warping thing. Thanks.

The real question is whether there is a minimum or maximum angle in some code. I'd bet there isn't. It's probable written diffrently. I'd guess the code would be in terms of winds and safety factures. Why don't you just check out a sectional for the area?

Lee

even easier, just copy the coordinates from google earth and put them into the FCC antenna search. then you will get a much more accurate idea of the height of tower. if it's there, it will be in the database.

or buy a sectinoal. it's even better/more accurate as it pertains to jumpers and it comes with a road map of major highways.

No need to buy sectionals anymore.

http://www.skyvector.com

_justin

 must take into account the angle the pic was taken from??? very unlikely it was 90 degrees overhead.

right on, i was gonna also recommend skyvector for sectionals... but, i would venture to say that the FCC site will be more accurate, most of the time.

when surveying tower info, some monkey has to climb up there and measure it with either a tape drop or a real nice laser range finder. the company i moonlighted with were sticklers about being accurate within inches. of course, it also depends on whether or not that info makes it to the FCC site, but in theory it should. either way, it's mostly accurate within a few feet. on the other hand, i've seen sectionals that were off by a hundred feet or more.

just food for thought.

oh, and i forgot to add...

the other reason i prefer the FCC site is that as a jumper, you only want to know the height above ground without appurtenances. since you will probably not climb or jump from a 30ft fiberglass antenna mast, grounding rod, etc. etc.

Pope.,
..... have you been hanging out with wwarped?

What about basing it of off the height you are looking at the antenna at? Ie you are looking at an "A" from 1 mile up on google earth?

Doesn't help if you don't know the angle at which the satellite is.

What about the shadow of the a to determine the sun angle......
Blah BLah

That works if your dealing with straight lines.

Cables on A's are never straight. Figure out the height from the base to each cable insertion and from there you can figure it out.

On bigger A's I believe they run every 110 feet. So if you have 10 cables attached to the A=1100 +/-?

I was hoping the seriousness of my geometry drawing reflected the seriousness of my reply,

how ever,

I find flaw in your theory, I have an A that is 1500ft and some, and it has only six wires going up. The reason I know it is 1500+ is the big sign at the driveway and the web site says it is also.

So the wires are 250 feet apart. It all depends on the tower. So yours is 1500 feet / 6 wires = 250

I've been on some that are 110 apart and others that are 150.

Figure it out relative to the object in question. Its not an always 110 feet apart.

this is not aimed at anyone in particular... but,
why the hell must you all make it so hard?!!

for fuck's sake! how many times must we go over this. there is NO standard in towers.

i just told you how to find the (actual) height. stop making it more difficult than it is.

that is all.

   also depends on angle of wires, and to what tension they have been pulled..... gravitational pull of the moon may also come into effect at this point.
i would seriously contemplate jumping.

Perhaps Pope is researching towers in Alberta.

You could do it with a sun path diagram for the area but than you need the date and time of day the photo was taken...

the idea for using satelight photos to determin the height of As in the US was a good idea, sure, but the fact that even after SEVERAL excellent reasons NOT to do it have been put forth, you guys are still into it?


reason ONE: towers have non-standard wire-anchor-foundation measurments
TWO: pictures of As even at best quality Google Earth Pro, are not good enough to determine where on the tower the wire hits accurately.
THREE: identifying towers on GE means you know where they are and you should go measure it with a goram laser in person.
FOUR: even if the resolution was good enough, ALL Google earth images are very intentionally 'distorted' to counteract the fact that in satelite photography the picture is 99.999% of the time from no where near directly over the subject, (this provides photographic contrast and quality in shadows, as well as the fact that satellites are taking pictures at the convenience of their orbits, and do not 'reposition' themselves for pictures, they just happen to be flying past the area where they can look to the side) meaning all google earth photographs suffer from PERSPECTIVE DISTORTION, warping the image BEFORE it goes onto GE, then GE further messes with it to make the non-flat, 2D image fit onto a perfectly square 3d topographical data.
http://en.wikipedia.org/...ortion_(photography)
FIVE: EVER IF there was no resolution proplem, identification accuracy, or perspective distortion, a FAA sectional is accurate to the foot, ALWAYS current withing a few months, and provides tower idents and coordinates as well as a major road map.

As Blitzkrieg and others have said succinctly
the use of internet data, a laser range finder,
and my Suunto has always proved efficient.

However, this long back and forth reminds me
of an old science joke my dad told me long ago:


On a science test: Describe how you could use a
barometer to determine the height of a building.

1) Take atmospheric at ground level, get to the
top and take a reading, compare and use math.

2) Use the shadow of the barometer and the
shadow of the building and some trig.

3) Go to the top and drop it, count the number
of seconds to impact and do the math.

4) Find the building's superintendent and tell
him, "Hey buddy, I will give you this nice nifty
barometer if you tell me how tall your building is"

 
I think those are some of the best answers yet. Is this really the state of American education? I grant you I can't spell for shit but I at least remember my trig.

Lee

Where is America?

use your satelite photos

Problem is that you would have to know how to speak and read english

OK all...everybody calm the fuck down now. I appreciate everyone's answers, and carefully considered each one of them. That being said, I finally figured out the best way to determine the height of said antenna:

Step 1: I got in the car.
Step 2: I drove to the antenna.
Step 3: I put on my rig and climbed the antenna (having measured the rung spacing on the ladder and counted rungs)
Step 4: I jumped the antenna.
Step 5: Packed and repeated for an accurate sample.

The tower is 820 feet.

I still appreciate Sat imagery to locate antennas especially when I'm in unfamiliar territory as I am now. Combined with sectionals it's a winner.
cheers all!
pope

win

epic win.

so were the rungs 15"?

12" rungs.

well, that makes things easy.

Yea it does, I hate having to do math at the top of a tower...