Chapter 2
2 Introduction
ART tracking systems are infrared (IR) optical tracking systems. In this user manual we
are going to perceive "tracking" as measurement of positional and rotational information
(i.e. orientation) of objects or individuals that move in a defined space.
Concept of tracking The simultaneous measurement of spatial position (X, Y, Z) and
orientation (three independent angles) is called "six degrees of freedom" (6DOF) track-
ing. If only the spatial position (X, Y, Z) is to be measured it is called "three degrees of
freedom" (3DOF) tracking.
Single markers are sufficient if only 3DOF coordinates are needed, but single markers
cannot be identified. DTrack2 will assign an ID to a tracked 3DOF marker as long as it
can be followed, but after losing the tracking (e.g. due to occlusions) it will not be able to
re-identify the marker and thus assign a new ID.
For 6DOF tracking, however, a target is mandatory. Targets are unique and rigid ar-
rangements of markers (=rigid bodies) and thus can be identified by their relative marker
position. Figure 2.1 on page 17 shows the concept of infrared optical tracking with a two-
camera system and a standard target.
Figure 2.1: Concept of optical tracking (stereo vision)
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