Detect direction of motion

Hi,

Could I use ultrasonic or light sensor or anything else to detect
direction of 2D motion including left/right and up/down? I need to
know the exact direcion.

Thanks!

terry <leonlai2k@yahoo.com> wrote:

> Could I use ultrasonic or light sensor or anything else to detect
> direction of 2D motion including left/right and up/down? I need to
> know the exact direcion.

Yes (and obviously so, since you included "anything else" in the list
of possible options ;-).  But it'll all depend on whether you want to
measure motion in a closed room, or out in the open.  Without walls to
reflect sound or light off, or some other feature that can be observed
to change, it's essentially impossible to measure movement.

But does any of this have to do with algorithms of computer graphics?


-- 
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

terry wrote:
> Hi,
> 
> Could I use ultrasonic or light sensor or anything else to detect
> direction of 2D motion including left/right and up/down? I need to
> know the exact direcion.
> 
> Thanks!

If you need only direction after a change in direction, use a 2D
accelerometer.

-- 
------------------------------------------------------------
Creepy, Soulless Gigolo for President ? NOT !
---------------------------------------------
THK is one weird, weird something.

On 8 Aug, in article
     <9904d48.0408080914.54c8f0f6@posting.google.com>
     leonlai2k@yahoo.com "terry" wrote:
>Hi,
>
>Could I use ultrasonic or light sensor or anything else to detect
>direction of 2D motion including left/right and up/down? I need to
>know the exact direcion.

Yes.

Oh you want a more detailed answer, without more details especially
about the object, distances, response time, frequency of results, and
environment no more details can be given.


-- 
Paul Carpenter		| paul@pcserv.demon.co.uk
<http://www.pcserv.demon.co.uk/>        Main Site
<http://www.gnuh8.org.uk/>              GNU H8 & mailing list info.
<http://www.badweb.org.uk/>             For those web sites you hate.

Hans-Bernhard Broeker <broeker@physik.rwth-aachen.de> wrote in message news:<2nn6nnF2gp65U3@uni-berlin.de>...
> terry <leonlai2k@yahoo.com> wrote:
> 
> > Could I use ultrasonic or light sensor or anything else to detect
> > direction of 2D motion including left/right and up/down? I need to
> > know the exact direcion.
> 
> Yes (and obviously so, since you included "anything else" in the list
> of possible options ;-).  But it'll all depend on whether you want to
> measure motion in a closed room, or out in the open.  Without walls to
> reflect sound or light off, or some other feature that can be observed
> to change, it's essentially impossible to measure movement.
> 
> But does any of this have to do with algorithms of computer graphics?


The device could be used outdoor or indoor.

But not totally dark envirnment

terry <leonlai2k@yahoo.com> wrote:

> The device could be used outdoor or indoor.

That doesn't give the necessary information.  Let me show you why:
imagine your device is were to use an optical pattern-recognition
(rather than signal echo timing) based method.  If you try to use that
device outdoors, and 'outdoors' just happens to be right in the middle
of one of the salt seas of Utah, it'll fail completely, because the 
environment will look exactly the same, no matter how fast it moves.

Ultimately, you need something external to the object that specifies
what "being at rest" means to your device, because physics doesn't
provide you with any such thing.  That's what Einstein's Principle of
Relativity really says: there's no such thing as absolute speed (and
thus no way to measure it, either).  So you have to measure speed
relative to *something*, and the device must be able to determine
where this "something" is.

Optical pattern recognition would work in some cases (like in the
optical mouse you may have attached to your computer), ultrasound can
work, too (or bats wouldn't manage to catch anything at night).

-- 
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

"terry" <leonlai2k@yahoo.com> wrote in message
news:9904d48.0408080914.54c8f0f6@posting.google.com...
> Hi,
>
> Could I use ultrasonic or light sensor or anything else to detect
> direction of 2D motion including left/right and up/down? I need to
> know the exact direcion.
>
> Thanks!

How about a 3D inertial measurement sensor? Not cheap but it should do the
job..
http://www.xsens.nl/

Rob

On Mon, 9 Aug 2004 15:50:18 +0200, "Rob Turk"
<wipe_me_r.turk@chello.nl> wrote:

>"terry" <leonlai2k@yahoo.com> wrote in message
>news:9904d48.0408080914.54c8f0f6@posting.google.com...
>> Hi,
>>
>> Could I use ultrasonic or light sensor or anything else to detect
>> direction of 2D motion including left/right and up/down? I need to
>> know the exact direcion.
>>
>> Thanks!
>
>How about a 3D inertial measurement sensor? Not cheap but it should do the
>job..
>http://www.xsens.nl/

   Is there any way to focus those little optical mouse sensors on
infinity (or a couple of feet on out to infinity)? I would think those
would work well against a fixed background, and they're cheap.

>Rob
>

-----
http://mindspring.com/~benbradley

>    Is there any way to focus those little optical mouse sensors on
> infinity (or a couple of feet on out to infinity)? I would think those
> would work well against a fixed background, and they're cheap.
> 
> >Rob
> >
> 
> -----
> http://mindspring.com/~benbradley

No. This does not work when light is insufficient.

On Tue, 10 Aug 2004 07:07:01 -0700, terry wrote:

>>    Is there any way to focus those little optical mouse sensors on
>> infinity (or a couple of feet on out to infinity)? I would think those
>> would work well against a fixed background, and they're cheap.
>> 
>> >Rob
>> >
>> 
>> -----
>> http://mindspring.com/~benbradley
> 
> No. This does not work when light is insufficient.


The more complicated solution would be accelerometers and laser gyroscopes
to computer distance moved.  Bloody complex if u ask me though I've never
done it myself.