[aprssig] bad PHG, or lots of big towers?

[Larry Cerney]

-----Original Message-----
From: aprssig-bounces at lists.tapr.org [mailto:aprssig-bounces at lists.tapr.org]
On Behalf Of Chris Rose
Sent: Wednesday, December 15, 2004 3:56 PM
To: TAPR APRS Mailing List
Subject: Re: [aprssig] bad PHG, or lots of big towers?

I would still ask exactly what is average terrain?
[Larry Cerney] An average of the elevation surrounding the tower out to a
given distance, say 10 miles.  Pick distances out from the tower say 1 mile,
2 miles, 3 miles etc.  Draw a circle at those distances around the tower.
Draw lines from the tower out ever 45 degrees from North. I.e.:
0,45,90,135,180 etc.  Determine the elevation of the location at each
intersection of a line and a circle.  Add all the elevations together and
divide by the number of elevations added together and you get "Average
Terrain."   
  
Is it the spot of ground the tower sits on or is it
something else?
[Larry Cerney] It is something else. See above

If a small mountain say 5k high sits in the middle of
a plain somewhere, from where is the average terrain
found? 
[Larry Cerney] If the plain's elevation "averages" out to be 1000 Feet, a
tower on the 5000 foot mountain would be 4000 feet above "average terrain".
The mountains 5000 feet minus the 1000 feet of the average terrain equal
4000 feet above "average terrain."
 
The base of the tower or the flat land at the base of
the mountain?
[Larry Cerney] Flat land at the base of the mountain is the "Average
Terrain."

73....
Larry

Chris 
KB8UIH

--- Steve Dimse <k4hg at tapr.org> wrote:

> On 12/14/04 at 9:38 AM Gerry Creager n5jxs
> <gerry.creager at tamu.edu> sent:
> 
> >Height Above Ground at the tower base.  So: What's
> the Height Above 
> >Average Terrain?  That is, in my opinion, the
> height that should be 
> >advertised.
> >
> Not just an opinion, the spec is very clear on the
> fact that the H in PHG is
> above average terrain...
> 
> Steve K4HG


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