[TowerTalk] Locating Tower Guy Points

[Jim Lux]

This is what surveying is all about.  A reasonably competent surveyor could 
come out and stake out everything you need fairly quickly. You could 
probably do it yourself, if you had a friend to help hold the rod and you 
run the transit.

The whole process is based on making reasonably precise measurements of 
angles from mutually visible spots.  You might be able to do it with an 
inexpensive laser level and a ruler, if you're into improvising and doing 
things from first principles.  The problem is that the usual laser pointer 
has a pretty big spot 100 feet away.

A run of the mill transit (which you can rent, or possibly borrow) can 
easily make measurements to 1 part in 1000 (i.e. an inch at 100 ft).

If you have a sailor's sextant, it can make measurements of the needed 
precision.

Differential GPS is another way (and is dead easy.. it gives you position 
in UTM grid coordinates.

If you have a college near you, maybe you could schmooze the civil 
engineering folks into doing it as a class exercise?  Or, if you've got a 
buddy in the public works department or who's a contractor, etc.






At 12:07 PM 12/22/2003 -0600, 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 at contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk