Newsgroups: comp.robotics
Path: brunix!uunet!think.com!mips!darwin.sura.net!udel!rochester!cantaloupe.srv.cs.cmu.edu!crabapple.srv.cs.cmu.edu!netnews.srv.cs.cmu.edu!gerry
From: gerry@cmu.edu (Gerry Roston)
Subject: Re: Dead reckoning
Message-ID: <GERRY.92Apr11190812@onion.cmu.edu>
Date: Sun, 12 Apr 92 00:08:12 GMT
Organization: Field Robotics Center, CMU
Nntp-Posting-Host: onion.frc.ri.cmu.edu
In-Reply-To: gat@forsight.jpl.nasa.gov's message of 10 Apr 92 16:41:26 GMT
Reply-To: gerry@cmu.edu (Gerry Roston)
References: <NIVEK.92Apr9170542@scythe.frc.ri.cmu.edu> <GERRY.92Apr10110253@onion.cmu.edu> <1992Apr10.164126.25875@elroy.jpl.nasa.gov>
Distribution: comp.robotics
Lines: 41

In article <1992Apr10.164126.25875@elroy.jpl.nasa.gov> gat@forsight.jpl.nasa.gov (Erann Gat) writes:
   In article <GERRY.92Apr10110253@onion.cmu.edu> gerry@cmu.edu (Gerry Roston) writes:
   >  I suspect that when
   >we repeat these tests as the Ambler walks around outdors, that the
   >error will be less.  [Why?  Because I suspect that the error in my
   >ground truth measurements were high due to the confined conditions of
   >the building in which the earlier tests were done.]

   Why whould confined conditions increase ded reckoning errors?  Is the 
   robot bumping into the walls?

Let me explain the measuring technique used:  We mounted a number of
retro-reflectors on the Ambler.  These devices are nifty little prism
do-hickeys that take a beam of light within some range and reflect it
back to its origin.  These devices are used by surveying instruments
and the intention is that the angle of incidence is small (although
they have an included angle of 45 degrees).  Anyway, by measuring the
position of three of these (rigidly mounted to the Ambler), we can
calculate the position of any point on the body.

The device used to measure these points was a surveying instrument, a
device typically used to measure distances of up to miles, not less
than 15 meters.  So, within the building, the Ambler was too close to
properly focus the sighting telescope, the angle of incidence became
quite large as the Ambler approached the measuring station, the
position of the measuring station was such that is was akward to use,
etc.  While I can sympathoze with Erann in that my original statement
runs against ordinary intuition about measuring, because of the
circumstances in this instance, I stand by my earlier statement.

--
Gerry Roston (gerry@cmu.edu)    | The most foolish mistake we could possibly
Field Robotics Center,          | make would be to allow the subjected people
Carnegie Mellon University      | to carry arms, history shows that all
Pittsburgh, PA, 15213           | conquerors who have allowed their subjected
(412) 268-3856                  | peoples to carry arms have prepared their own
                                | fall. Adolph Hitler
The opinions expressed are mine | 
and do not reflect the official | 
position of CMU, FRC, RedZone,  | 
or any other organization.      | 
