  The moment method is an image analysis technique for sub-pixel estimation of
particle positions. The total error in the calculated particle position
includes effects of pixel locking and random noise in each pixel. Pixel
locking, also known as peak locking, is an artifact where calculated particle
positions are concentrated at certain locations relative to pixel edges. We
report simulations to gain an understanding of the sources of error and their
dependence on parameters the experimenter can control. We suggest an algorithm,
and we find optimal parameters an experimenter can use to minimize total error
and pixel locking. Simulating a dusty plasma experiment, we find that a
sub-pixel accuracy of 0.017 pixel or better can be attained. These results are
also useful for improving particle position measurement and particle tracking
velocimetry (PTV) using video microscopy, in fields including colloids,
biology, and fluid mechanics.
