Page 166 - Anthropometry, Apparel Sizing and Design

Full body 3-D scanners 161

Fig. 6.12 Image of a physical landmark (a dome of a known dimension, highly engineered for a
reliable size and shape) and a double-sided adhesive doughnut that ensures the dome can be
precisely placed over a point landmark. This landmarking system is provided by Human
Solutions.

Most scanner software developers recognize that the computer algorithms will not
always place landmarks reliably and therefore make provision for easily indicating a
different landmark point and retaking measurements. A trained operator can often
improve the reliability and validity of a study by checking the measurements on a scan
as they are taken and visually correcting landmark placement as necessary. In any case,
scans should always be checked before the scanee leaves the booth to retake a scan if the
person was not in the right position or if the scan is not optimized for some reason.
For optimal reliability of a study in which measurements will be derived, it is nec-
essary to place landmarks manually, palpating for joint centers and marking the land-
marks that are critical and cannot be reliably located automatically. If the scanner has
capability to capture color or grayscale information along with the scan, then land-
marks can be set with a washable marker or with an adhesive dot. If the scanner only
takes XYZ coordinate data and no color information, a dimensional landmark can be
used. Human Solutions makes a very precise dome, 20mm in diameter that can be
captured in the scan (see Fig. 6.12). As the size of this dome is known, the precise
landmark point can be identified at the top of the dome and transferred down to
the surface of the scan. The bump of the landmark can then be removed from the scan.
Of course the advantages of scanning over manual measurements are the compar-
atively short amount of time needed with each study participant and the fact that
highly trained assistants are not needed to conduct the study, as is true of a manually
conducted anthropometric study. Manually placing landmarks adds time and requires
skillful assistants, increasing the time and expense of an anthropometric study con-
ducted with the scanner. However, if the number of manual landmarks is kept to a
minimum, this training need not be overly extensive, and the study can be optimized
for both reliability and cost.

6.7 How to assess scanner technologies for various
end uses

With such a wide array of scanning systems available, with different capabilities,
strengths, and weaknesses, scan systems exist for every end use. To decide the
appropriate system for any one goal, many factors should be considered. Though