Browse Prior Art Database

Position Calibration in Virtual World Space

IP.com Disclosure Number: IPCOM000103810D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 4 page(s) / 88K

Publishing Venue

IBM

Related People

Wang, CP: AUTHOR

Abstract

Disclosed is a method to simplify the determination of coordinate axes of position tracking devices by taking a quick three points measurements.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Position Calibration in Virtual World Space

      Disclosed is a method to simplify the determination of
coordinate axes of position tracking devices by taking a quick three
points measurements.

      The Polhemus position tracking device consists of a source
device that generates pulsed directional signal and a sensor that
picks up the signals and with appropriate software converts them into
position and orientation data such as x, y, z, azimuth, elevation and
roll.

      The coordinate axes of the virtual space is always a right hand
system with the x-axis pointing to the right, the y-axis pointing
upward and the z-axis pointing at the observer.  The orientation of
the coordinate axes of the source and sensor, however, depending on
how they are installed.  To correctly map the sensed position data to
the virtual space, one must determine in advance the  coordinate axes
of both the source and the sensor.

      Although the source can be installed in a variety of
orientations, it is almost always true that two of its major axes are
parallel to the ground.  Under those conditions the coordinate axes
of the source can assume only one of 24 possible orientations.  For
brevity, 12 of those orientations are tabulated in Fig. 3.

      By making a few judicious position measurements, one can deduce
the exact axes orientation without ambiguity.  Those measurements can
be done without detailed understanding of the internal working of the
source and sensor devices.  Figure 1 is a typical installation of the
position tracking device with the respective axes of source and
sensor.

      Fig. 2 shows a rectangular volume in real space used for
calibration.  To calibrate, place the sensor at the upper left most
corner P1 of this rectangular volume and record its three position
values x1, y1 and z1.  Next move the sensor to the lower left most
corner P2 of the same volume and record its positions x2, y2 and...