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RE: In-building location determination using wireless?

From: "McCarty, Paul" <>
Date: Fri, 30 May 2003 09:07:42 -0400

I would say this is next to impossible. We've looked into various
methods of augmenting GPS and since 802.11b, etc. doesn't have a
directional antenna (nor would I venture to guess how difficult this
would be to build), you have to rely on triangulation and signal
strength, or triangulation and timing of packets (similar to gps). I
know there are some hooks to measure signal strength, but all it takes
is one wall thicker then another and you lose signal strength. Or a
floor say? You'd be better off writing coordinates on the wall! :-)

Another alternative is they sell GPS repeaters. But I imagine this is
very expensive!

I would suggest looking into an intertial/accelerometer sensor. This not
only would be much more accurate, it would give you the added benefit of
3d positioning. There are lots of reasonable priced ICs. Check out
Motorola low-g sensor ICs, like this one:

http://e-www.motorola.com/brdata/PDFDB/docs/MMA1270D.pdf
http://e-www.motorola.com/brdata/PDFDB/docs/MMA1220D.pdf

This one is only one dimension, but $20 from digikey. You can imagine
how to use 2 or 3 to get the other dimensions. There are also 2/3 d
varieties out there from other manufacturers but they tend to be pricey
and meant for higher gs.

-Paul

> -----Original Message-----
> From: Steve Barr [mailto:]
> Sent: Thursday, May 29, 2003 5:24 PM
> To: 
> Subject: In-building location determination using wireless?
> 
> 
> Since GPS does not work indoors, I was looking into using
> an 802.11b network for location determination.
> 
> Anyone know of something like this that's available
> for use?
> http://research.microsoft.com/~bahl/MS_Projects/projects.html#radar
> 
> This project doesn't seem to be live:
> http://sourceforge.net/projects/locationserver/
> 
> Thanks!
> 
> Steve
> -- 
> http://www.stevebarr.com
> 100% my opinions.
> 
> 
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