The size distribution of all three axes can be plotted
(Fig. 4) with good accuracy [6]. The placement of the
particles in the standing position requires a visual evaluation
of the longest axis of the particles and then physical
placement of the longest axis perpendicular to the sand bed.
As stated above, to test the reliability and variability of this
method, each of the samples has been imaged 10 times. The
standard deviation of the results from the 10 images is very
low (Table 1). Thus the error introduced due to placement is
not significant [6]. The lower size limit of particles that can
be placed in a standing position has, for this study, been 1
cm. This has in part been due to the size of the luminous
beads; they have a diameter of about 4 mm. If finer grained
luminous beads were used the lower size limit would be
dependent upon the ability to place the particles correctly in the defined standing position; as small as 5 mm may be
possible