I think an angular accelerometer would be more useful. With an angular accelerometer you could determine which direction the device is pointing (landscape or vertical). The GPS can then be used to determine position.

-RobB

On 7/23/07, 4837jw@latitools.com <4837jw@latitools.com> wrote:
A really cool application for the accelerometer is relative position
calculation.  Combine this with the GPS and you can achieve relatively
high resolution position data.

The potential robotics appications are tasty.

See the datasheet link at the bottom of this page:
http://docwiki.gumstix.org/Frequently_asked_questions/Goliath_boards

James

>
> On Jul 23, 2007, at 1:06 PM, Black, Michael wrote:
>
>> Actually an accelerometer will show 1G at rest and 0G during free-
>> fall.
>> Just one change occurs from rest to free-fall (i.e. 1G...0G).
>> And you need to be sure that you have the vertical axis being measured
>> -- otherwise you need a 2 or 3 axis accelerometer.
>
> This is a 3-axis accelerometer.
>
>> You're not actually accelerating during free-fall (your
>> acceleration is
>> constant) -- but your velocity is increasing.
>> Here's some good info on the math...
>> http://www2.usfirst.org/2005comp/Manuals/Acceler1.pdf
>
> You are actually accelerating during free-fall, at a constant 9.8m/
> s^2.  Your velocity cannot change unless you're accelerating.  The
> accelerometer is not really measuring your acceleration, it's
> measuring strain on a MEMS crystal; when you're at rest, the crystal
> is being tugged on by gravity, but the table or whatever you're
> sitting on is countering that force, and thereby creates strain in
> the crystal.  When you're in free-fall, you're accelerating at the
> same speed as the crystal, so there's no strain in the crystal, and
> so it measures 0.
>
> C
>
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