Newsgroups: comp.robotics
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From: seeker@indirect.com (Stan Eker)
Subject: Re: Indoors positioning problem
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Date: Fri, 2 Jun 1995 08:45:16 GMT
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Nancy Hendler (equant@Walden.MO.NET) gabbed:
: Patrick M Brennan (pbrennan@world.std.com) wrote:
: : Roar :

: : You have put your finger on a set of extremely difficult and
: : complex problems which are still on the active & unsolved list
: : as far as most roboticists today are concerned.

: : : ...I have assumed that it is possible
: : : to measure the distances within say 0.5% margin, and that it be possible
: : : to narrow the beam down to a degree, giving 360 separate measurements
: : : round the circle. Do in fact such hardware exist at a reasonable
: : : price? 

: : There are so-called Laser Radars, and they have very interesting
: : properties, but neither of us can afford one.  I think your 0.5% is
: : far too optimistic, not to mention your one degree beamwidth.

: I saw in a book titled "best of circuit cellar vol ?" a sonar style 
: ranging system that took 360 samples of the room around it, and fed it to 
: the pc to handle.  Sorry, I don't remember what volume it was in.

Doesn't matter (much), as the electrostatic transducer used in the Polaroid
ranger in the old article isn't anywhere *near* a 1 degree beamwidth, more
like 40 degrees.  The biggest and earliest return in the beam is what you'll
see, so doing any more than about 16 positions per circle is useless.

With some sort of `shotgun mic' tube on the front, you could POSSIBLY reduce
the beam width, but I haven't tried it or seen it done.

