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

Gerry Creager n5jxs gerry.creager at tamu.edu
Tue Dec 14 15:38:34 UTC 2004


We can wander off into a number of discussions here.  I suspect there 
are more than 180 towers in the world over 2k feet.  That's actual 
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.

I'll offer that there are a  number of folks who look at the MSL height 
(no, *NOT* altitude) and add the AGL (above ground level) height to 
that, post it and call it good.  It's misleading, as that number gives 
little useful PHG information unless you abstract the MSL height at the 
antenna and run it through a program designed to use those values 
(RadioMobile comes to mind) to calculate range estimates.

<Pedantic academic rant>
Of course, we should have abandoned NGVD29 Mean Sea Level heights long 
ago in favor of NAVD88 orthometric heights as mandated for and by the 
National Geodetic Survey.  That should keep most users busy for some 
time trying to get their GPS to report same...

Sea level isn't really level...

</Pedantic academic rant>



Jason Winningham wrote:
> Looking through the data Bob posted I find 46 digis with advertised 
> heights of 5120ft (a mile!) and 140 with heights of 2560 ft.
> 
> Are there 186 towers over half a mile high with digis on them?  Are 
> there even 186 towers over half a mile high in the world?
> 
> Or are there a bunch of operators who don't know the difference between 
> height and altitude?
> 
> OK, the last one was rhetorical, but the first two were serious: are 
> there really that many tall towers around?
> 
> -Jason
> kg4wsv
> 
> 
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-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020
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Office: 903A Eller Bldg, TAMU, College Station, TX 77843




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