[RE-wrenches] GPS units

[Matt Tritt]

I used to have a WW II aircraft altimeter (out of an Aircobra) installed 
in a Diesel LandRover when I first started pump work years ago. The 
instrument took all the guesswork out of sizing pumps, and let me know 
when the naturally aspirated Diesel was going to be making more smoke 
than horsepower. An altimeter needs to be set every time you head out, 
but they are accurate to within a few feet. Over the years, I have used 
GPS, shot in elevations with transit and rod, used fine elevation topos 
and guessed. :-) I agree that the only really accurate method, if 
available, is to use a pressure gauge on existing plumbing, but an 
altimeter is a close second and a GPS third.

Matt T

Jason Lombard wrote:

> William,
>
> Topographic maps are great if your familiar with them. A laser if you 
> can afford it or the best I have heard of is fill a tube or pipe with 
> water from the pump to your tank and measure the psi at the base of 
> it. The calculation is 2.31 feet of lift for every psi. Not everyone 
> has their piping rolled out or on site yet so this could be a 
> challenge and again is very accurate.
>
> BTW - GPS units are inaccurate to the extent that they are 40 feet off 
> horizontally and 90 feet vertically. This means you could be up to 130 
> feet off. Big difference when your sizing for particular pump out put.
>
> Good luck,
>
> On Tue, Jan 27, 2009 at 2:34 PM, William Miller <wrmiller at charter.net 
> <mailto:wrmiller at charter.net>> wrote:
>
>     Does anyone have a foolproof tool to measure elevation?  I have
>     researched GPS units recently.  They are notoriously inaccurate
>     for elevation:
>
>     http://wiki.motionbased.com/mb/GPS_Unit_Elevation
>
>     Here are few more links with GPS fundamentals:
>
>     http://www.adventurenetwork.com/cgi-bin/adventurenetwork/GPS_101.html
>     http://www.gpsreview.net/electronic-compass/
>
>     I have a Suunto Observer watch with an altimeter.  I think I can
>     get relatively accurate measurements of DIFFERENCE in elevation if
>     I measure the two elevations in quick succession.  I will be
>     trying it.
>
>
>
>     William
>
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> -- 
> Jason Lombard
> Open Hand Solar LLC.
> Certified Sustainable Building Adviser
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