Didier makes a good suggestion. A couple of gotcha's to watch out for:
1) If the copy is a photocopy (as opposed to a photographic print, or a
blueline from a vellum original), there's some chance that it's distorted a
bit. Most photocopy machines have a different enlargement/reduction ratio in
one axis from the other. Depends on vintage, etc., but it's mostly because
one direction is done optically (relay lens scheme), and the other
mechanically (scanned). Easy to check this.. measure (with a scale)
something of known dimensions in each direction.
2) If there are significant changes in grade (elevation), then you might not
want the guy anchors spaced evenly on the plan. You probably want the
vertical angles all the same, which means you might need to move an anchor
in or out: imagine if one anchor is on a 20 foot high hillock..
(This is one of those areas where getting an engineer to look it over might
be a good plan..)
--------
By the way, given how much people need to use transits, etc, and simple
surveying for putting up towers, someone might want to get ambitious and
write up a simple "how to" for publication. If you've got a club, buying a
decent used theodolite, tripod, and rod isn't all that expensive, and is an
incredibly useful thing (if nothing else, the 20-40x scope on the theodolite
gives you a way to look and see if the feedline fell off that antenna 100
feet up...)
There's also some new electronic compass integrated into a monocular type
devices, but, I doubt they have the accuracy required.
Leica Geosystems has some new fairly inexpensive (for surveying equipment!)
laser distance meters (<$500) that have impressive performance. (Leica is
Wild/Leitz/etc...) (100m, 3mm accuracy, $300)(0.1 inch out of 330 ft)
One might be able to do the surveying with something like a Brunton Pocket
Transit, but it would be touch and go.
----- Original Message -----
From: "Didier Juges" <didier@cox.net>
To: "Tower Talk" <towertalk@contesting.com>
Sent: Wednesday, December 24, 2003 11:40 AM
Subject: [TowerTalk] Re: Locating Tower Guy Points
> I suggest you try to get a copy of the survey from when you bought the
> property. It should include references to landmarks that should still be
> there on the other side of the house. From there, you can draw your tower
> project on the same print and you can easily figure out where the anchor
> points should be, with respect to these landmarks.
>
> Now, for such a large tower, you will certainly need a permit, in such a
> case the designer should do these calculations so the engineer can sign
the
> drawings.
>
> 73,
> Didier KO4BB
>
> At 12:07 PM 12/22/2003, Bob Gates wrote:
> >I'm perplexed. And for those who know me, just shut up. Am in the
planning
> >stages of installing a "really big tower". At least it's larger than
anything
> >else I've put up. The question is, how do you locate the positions of
the guy
> >wire base points when they are not on a direct line of sight with the
tower
> >base?
> >
> >For example, say I want to install 100' of Rohn 45/55. These towers
require
> >fairly large anchor rod foundations. Something in the neighborhood of
> >3'x3'x4'
> >and 6' deep. Exact size is not an issue, but one would hopefully be able
> >to dig
> >the holes and pour the concrete/rebar at the same time you pour the tower
> >foundation. But suppose one or more of the anchor points is on the other
side
> >of a structure, say a house. You can sort of approximate the distance
> >from the
> >tower by knowing the length of the guy wire and calculating the angle of
the
> >dangle with a temporary pole. But the angle from the tower can't be
> >seen. And
> >they need to be 120 degrees apart.
> >
> >The only thing I can figure so far is to put in the tower foundation,
wait a
> >week or two, install 30' or so of tower, add some temporary guys, and
then
> >visually align where the anchor bolts need to be. Then have the
> >contractor come
> >back out and excavate/fabricate and install the anchor bolt foundations.
Then
> >wait a week or two before installing the permanent guys and erecting the
> >rest of
> >the tower. Obviously you would want to do all of this in one trip vs.
> >two, but
> >I can't for the life of me figure out how.
> >
> >Any advise from the experts would be most appreciated.
> >
> >Bob, KG7KW
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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