Area/Volume Centroid
Area/Volume Centroid
Once a particle has been identified, its location must be determined. In
line with the overall philosophy, the approach to determining the position
of the particle is relatively simple and is based on the centroid of the
particle.
Use Volume or Area centroid ?
Two centroids are calculated. The Area centroid (<A>) is the centroid of
the area occupied by pixels satisfying the required threshold. The Volume
centroid (<V>) is the projection onto the pixel plane of the centroid of
the image exceeding the required threshold. Normally the volume centroid
should be selected as this will typically yield a better estimate of the
particle's position. If the particle covers more than one pixel in each
direction, then the position of the particle may be determined with
subpixel accuracy. The accuracy is a function of the size of the particle,
the amount by which the peak intensity exceeds the threshold, and the noise
component of the image.
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DigImage User Documentation
Stuart Dalziel,
last page update: 19 February 1996