From: James Harrison <harrison@cs.ubc.ca>
Subject: TECH: `Passive' tracking of participants in a free space?
Date: Fri, 13 Nov 1992 14:20:44 -0800
Organization: Computer Science, University of B.C., Vancouver, B.C., Canada


We are designing an interactive-participant oriented exhibit that will
present the illusion of an audio and visual space to a participant.

To present these illusions we will be using spatially distributed
audio and visual sources (speakers and monitors) whose position,
orientation, etc will be well known and defined.

Knowing the position of the participant we will drive the audio and
visual sources to present the illusion of objects (invisible) through
the audio channels and the illusion of windows into a virtual-world
with the monitors.

The problem is in aquiring and tracking the position of the
participant.  We would eventually like to move to a system which did
not require the use of a active source carried by the participant.  A
passive reflector would be acceptable if it's cost was low enough, as
we may want to give the objects away as souvenirs.

The resolution of the tracker should be below 10 centimeters, and have
an update rate of at least 10/sec.  The system should be robust in the
presence of acoustically hard environments (echos or noise).  Be
useful in a large room (15m by 15m  by 3m at least).  Not require
extensive installation or calibration (beyond that which we will have
to do for the audio and visual sources).  And not require high
computational costs or special hardware (cheap, uniform, replaceable).

We're open to solutions using passive or active means, but we'd like
to limit the cost of the hardware/devices that the participant might
walk out of the door with.

I know that it seems like we're asking for a lot.  But we're looking
for suggestions and solutions that might require refinement.

If you have any suggestions, we'd appreciate hearing them.

Thanks in advance.

James Harrison