Using RSSI to locate an object

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I would like to use RSSI to locate an object in a 3D space. The space
will be a square box with transmitters located on the 4 corners. An
object will be place at certain positions within the box and I want to
be able to determine its location inside the box. Much like an
internal GPS.

I would like to know what components (IC's?) I need to perform such a
task.

Or if anyone else has any other more effective methods to acheive such
a task your comments are welcomed.

Thanks,

Josh


Re: Using RSSI to locate an object



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since RSSI devices (most of them) can output analog for a project that
you have in mind. a uC (microprocessor) would be suited for that.
   Look at the AVR line of programmable chips. You'll need a DEV starter
kit and learn a little about programming.
    THey have chips that offer multiple ADC (Analog to Digital ) converters.
  With these chips, they have enough power for a HID (Human INterface
device) or simply output some coded results to your computer via a
serial port and write some software.
   You may also want to look at Rabbit core embedded processors. With
those, the hassle has been taken out of making a board. etc.. look
them up on line.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
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Re: Using RSSI to locate an object




** Groper alert.

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** And when did you come up with this nut case idea?

    Or was it someone else's  ?


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**  How do you know it can even be done to any degree of accuracy ?


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**  You better explain the task much more clearly, with all the details.

 Or it qualifies as yet another:

" Novice needs help with  CRAZY  project"    TROLL.




......   Phil





Re: Using RSSI to locate an object


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When is your assignment due?

Do you have to use RSSI?
How big is your box?
Can you use any object?

One alternative way to do it would be with visual object recognition
using a camera on each side of the box.

For using RSSI I would have thought that you would have to use 4
receivers and the object is the transmitter?

Dave.


Re: Using RSSI to locate an object


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RSSI will indicate only the received signal strength, not distance -
and there are a lot of reasons why an accurate position indicator is
impractical using only this method, especially in the near field of
the TX antennas.

It certainly won't work for VHF and above. I have had some success
with short range position indicators using 125 kHz sources. If that is
feasible for you, please indicate the dimensions you are working with.

Frank Raffaeli
http://www.aomwireless.com /


Re: Using RSSI to locate an object



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Yes,  Frank is correct.

If the signal is attenuated in any way.... (eg by antena beam width, objects
absorbing RF,  RF reflections causing canceling or summing effect) then your
accruacy using RSSI will be shot.

You should read up on the internet about how GPS using timed signals and
sequences work to compute location.

There are so may problems using RSSI accurately for distance.


Regards
Joe



Re: Using RSSI to locate an object


On 3/19/07 5:03 PM, in article
snipped-for-privacy@n76g2000hsh.googlegroups.com, "Josh916"

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Which 4 corners of the 8-cornered box do you plan to use?

Don


Re: Using RSSI to locate an object



"Don Bowey"
 "Josh916"
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**  Suspect Josh is more your RSI type than RSSI.



.....   Phil





Re: Using RSSI to locate an object


snipped-for-privacy@n76g2000hsh.googlegroups.com...
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You can have a look at Chipcon's (now TI) CC2431 Zigbee transceivers : they
offer a hardware-based location detection feature.
See http://www.chipcon.com/index.cfm?kat_%20id=2&subkat_id12%&dok_id26%1 ,
claimed spatial resolution is 0,5m over a 64x64m area, with an overall
accuracy of 3m

Friendly,

--
Robert Lacoste
ALCIOM - The mixed signal experts
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Re: Using RSSI to locate an object


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GPS doesn't use RSSI, of course.

Is the task you want to perform the use of RSSI, or the determination of
position location with a box? What kind of accuracy do you hope to achieve?

Have you considered ultrasonic distance measurement?

Chuck

-

Re: Using RSSI to locate an object


The project is to locate a r/c boat in a roughly 2 to 3m^2 water
filled box, hence the transmitters or recievers will only be on the 3
or 4 walls of the box.

It will need to be fairly accurate considering the size of the box
relative to the size of the boat (i.e down to cm's).

We are also considering placing a webcam above the box and using image
processing to locate the boat, however I thought we might get more
accurate results using RSSI.

I hope that helps.

Josh

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Re: Using RSSI to locate an object



"Josh916" < snipped-for-privacy@gmail.com

** Really desperate Groper Alert !!


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 ** Huh  ??

 This is even  LOONIER that I thought !!


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**  Well, you thought wrong.




......   Phil




Re: Using RSSI to locate an object


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This detail would have been useful at the start!
So is it a 2 dimentional problem or a 3 dimentional problem?
i.e. can the water level vary?
If it can vary then you can use a simple water level meter and then
turn it into a 2 dimentional problem.

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Nope, not a chance. Visual object recognition is the way to go, with a
water level meter if needed.

Dave.


Re: Using RSSI to locate an object



"David L. Jones"

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**The OP is  utterly confused, he simply has no idea what " 3 dimensions"
means.

He describes a box in terms of square area   ???

He says the box is "filled" with water -  but is it  ??

He talks of an RC boat  - but is it really a RC submarine ??

Must be if the box is "filled"  with water, RC  submarines are available.

Ergo it follows....

The OP is a just another naive, code scribbler with  ZERO  comprehension of
physics or electronics.

They are now in plague proportions.




.......   Phil



Re: Using RSSI to locate an object


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Josh,

Your idea has been tried by big governments with big budgets.

NO, it will not work.

If you care to read a little, you may find a not so cheap way of doing
what you want:
http://en.wikipedia.org/wiki/Pseudolite

google has lots of links:
http://www.google.com/search?hl=en&c2coff=1&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=pseudolite&spell=1

good luck

If you find a way of getting this done, in any home made way,
please let us know.

donald

Re: Using RSSI to locate an object


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Thanks for everyones help, RSSI was mentioned to me by a fellow
academic and I'm at the stage of researching its possiblilites.

He seems to think that it is possible.

I will keep looking into it as I also have a backup plan using the
webcam.

---------------
AS FOR PHIL ALLISON I THINK YOU SHOULD LOOK AT THIS WEBSITE:
http://members.iinet.com.au/~rutlidge/alanindex.html IT SEEMS YOUR
REPUTATION PROCEEDS YOU.
---------------


Re: Using RSSI to locate an object


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This I would like to see.

I too tried in college to use ultra-sonic devices.

It was just too difficult to get a signal that would work.

I will admit the technology has improved 1,000 fold over the years.

However, physics has not.

Good Luck

I would be very interested in how you both get this done.

donald


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Re: Using RSSI to locate an object


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Josh, he is wrong.
It can be done (sort of) on a larger scale, but at the small scale you
are talking about it's just not possible as other posters have
mentioned. You would be lucky to determine if the object is inside the
box or outside, let alone its position inside.

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Seriously, start your backup plan now. Then it just becomes
essentially a software project.

Dave.


Re: Using RSSI to locate an object


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achieve?
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Having done some more research today it looks like other posibilities
include acoustic positioning or infrared positioning (e.g.
http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2004/rd73/476finalpro.htm )

What does everyone think about the other technologies mentioned above?


Re: Using RSSI to locate an object


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of
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achieve?
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(e.g.http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2004/rd ...)
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You are wasting your time, visual object recognition is the best
method in this particular instance. All the other methods (RSSI,
acoustic, and IR) require a transmitter on the boat and multiple
receivers. Visual recognition on the other hand doesn't require any
transmitter, will work with almost any size or type of object, is
simple, fairly accurate, will most likely only require one receiver,
and reduces the problem to essentially a software solution.

The decision is blindingly obvious.

Dave.


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