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Re: [TowerTalk] Trees, Mountains, 15 degrees...

To: "Pat Barthelow" <>, <>,<>, "Pete Smith" <>,"Jim Lux" <>
Subject: Re: [TowerTalk] Trees, Mountains, 15 degrees...
From: "Michael Tope" <>
Date: Mon, 24 Jan 2005 18:55:51 -0800
List-post: <>
----- Original Message -----
From: "Jim Lux" <>

> I believe it is the latter...
> In fact, the bottom of page 24 and the top of page 25 of hfta.pdf (Version
> 1.0) describes manually editing a .pro file to add a big mountain a long
> way away.
> I don't know if HFTA takes into account curvature of the earth and
> atmospheric refraction, though.  While for short distances (a mile or so)
> the error's only a few feet, when you get out to 10s of miles, the error
> starts to get bigger. Ignoring refractive effects you're looking at about
> 30m difference at a distance of 20km... a pretty small angle, though,
> perhaps a tenth of a degree.

Jim, et al:

I wonder if HFTA would have any problems with unevenly
spaced points. If you have a mountain that is 15 miles away
with a flat plain in between, you really want to conserve those
149 points so you have adequate resolution for the fine
structure of the mountain (as opposed to a evenly spaced
points which would mostly be wasted in the flat area
between the tower and the mountain). The desert areas
north of here are very typical of that situation. You have a
flat mesa for many miles, then a very high mountain range
(7 to 8K feet in some cases) which sets the angle of the
visual horizon and surely has an influence of the

73 de Mike, W4EF.............................


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