[RE-wrenches] GPS units

[Peter Parrish]

A caution to all. There are various types of GPS units, with varying
accuracies. The most accurate are spec'd at around +/- 6 feet. I have a
Garmin Etrex and under normal circumstances it delivers at that spec or
better (+/- 3 feet). Near tall buildings or in a steep canyon, the accuracy
goes to pot but for known reasons (multiple reflections of the radio
signals). I have no manufacturer's info on elevation, but knowing how GPS
units work, the resolution/accuracy in elevation should be roughly the same.


 

- Peter

Peter T. Parrish, President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com 

  _____  

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jason
Lombard
Sent: Tuesday, January 27, 2009 2:02 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] GPS units

 

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>
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

_______________________________________________
List sponsored by Home Power magazine

List Address: RE-wrenches at lists.re-wrenches.org

Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out participant bios:
www.members.re-wrenches.org




-- 
Jason Lombard
Open Hand Solar LLC.
Certified Sustainable Building Adviser
openhandsolar at gmail.com
505 795 8646

"I'd put my money on solar energy. I hope we don't have to wait 'til oil and
coal run out before we tackle that."

-Thomas Edison

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20090127/e06174dd/attachment-0003.html>