Page 161 - Anthropometry, Apparel Sizing and Design

156 Anthropometry, Apparel Sizing and Design

6.4.4 Scans in coordinate space

One other important issue is the origin point and the orientation of the scan in the coor-
dinate space. Different scanners establish the origin (the 0,0,0 point in the XYZ-axis) at
different points. Two popular choices for the origin are the center of the body being
scanned, or centered on a plane at the feet of the scan. Most Cartesian coordinate sys-
tems are oriented so that the X- and Z-axes are on the transverse plane, and the Y-axis is
up (Fig. 6.8), but other orientations are also used. Whatever the system, it is important
that the person being scanned is not rotated in reference to the coordinate system, but
is aligned with the frontal or sagittal plane of the body parallel with an axis. Often
when taking scans from one software to another, the scan will need to be transposed
into a different coordinate system. It is also important to know what the primary units
are used in each software and that the scan is imported into the correct system and
scale of measurements.

6.5 Reliability of scan generation from sensor views

The reliability of scan data is of course dependent on how reliably the XYZ coordinates
are sensed and recorded. Proper calibration should ensure this for all systems, using a
simple geometric object of known dimensions to check the system. The scanner soft-
ware must be designed to take the scan data from each sensor or camera and assemble
them into a 3-D model in a way that represents the body scanned accurately. This is not
an insignificant task. The data points define a complex organic shape. There are many

Fig. 6.8 This image shows a
Cartesian coordinate system with Z
in the vertical position. Most
scanners generate a scan with Y as
the vertical direction and X and Z on
the transverse plane.