Database Reference
In-Depth Information
22 (space coordinates) * 23 (edge cursors) * 48 (fl oating representations) * 50 (sampling
frequencies) = 1.21 MBits per second!
Clearly, an alternative representation is needed for more economic storage. These two
aspects of our study, the building blocks for representation and the storage of motion, are
now presented, suggesting a new model for motion representation.
THE MODEL
Our theoretical-conceptual model for the representation of motion data defi nes motion
variables using a binary approach (Spiegler & Maayan, 1985). It is the basis for a storage
scheme of a motion database.
Building Blocks
Motion is defi ned as the alteration of geometric relations between two adjacent links,
or between a body's links and the ground surface with which it comes into contact. The
alteration of the geometric relations between two adjacent links can be measure by three
angles referring to three spatial axes: pitch, roll, and spin axes.
Pitch angle: the extent of rotation of the limb/body on a vertical plane.
Roll angle: the extent of rotation about the longitudinal axis of the limb/body. This
determines the rotational state of the body.
Spin: (turn) angle — the extent of rotation about the vertical axis of the limb/body.
This determines the direction the body turns on a horizontal plane.
horizontal plane.
Figure 1 illustrates these terms graphically over a three-dimensional motion space.
Figure 1: Motion axes in three-dimensional space
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