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[aprssig] /A= altitude question

Stephen H. Smith wa8lmf2 at aol.com
Sat Aug 7 05:17:07 UTC 2010


  On 8/6/2010 9:48 PM, Greg Clark wrote:
> Guilty as charged -- negative altitude numbers are not something I have a lot 
> of experience with.  I'll take a look at it, but living at an altitude of 
> 100+ meters ASL, it's a little difficult for me to 'simulate' without driving 
> to the coast myself.
>
>

One place you can get to below sea level on a major highway (rather then 
somewhere remote like Death Valley) is Interstate 10 east of Palm Springs, 
CA.     In the Indio area where CA route 86 intersects I-10, the elevation is 
about -20 to -30 feet.     If you turn off the Interstate and head south on 86 
toward the Salton Sea, the level steadily drops.  At the Salton Sea, you are at 
about -200 feet.

I have driven this route (I-10) between Los Angeles and Phoenix many times, and 
have watched various GPS devices flirt with sea level and finally go negative a 
few feet for a stretch of about 3 miles.  It did not give UI-View, APRSpoint or 
APRSplus any problems.

It HAS given the FCC problems.    When I was working for Southern Cal Gas 
Company some years ago, we were trying to license a microwave shot with one end 
at a gas company headquarters south of the Salton Sea near El Centro, CA.    
The location here was at about 150 feet below sea level  -- the FCC online 
licensing system absolutely would NOT accept negative numbers.  We finally had 
to lie and record it as being at sea level!

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