Generalized Procrustes Analysis (GPA)
GPA applies the Procrustes analysis method to optimally superimpose a set of objects, instead of superimposing them to an arbitrarily selected shape.
Generalized and ordinary Procrustes analysis differ only in their determination of a reference orientation for the objects, which in the former technique is optimally determined, and in the latter one is arbitrarily selected. Scaling and translation are performed the same way by both techniques. When only two shapes are compared, GPA is equivalent to ordinary Procrustes analysis.
The algorithm outline is the following:
- arbitrarily choose a reference shape (typically by selecting it among the available instances)
- superimpose all instances to current reference shape
- compute the mean shape of the current set of superimposed shapes
- if the Procrustes distance between mean and reference shape is above a threshold, set reference to mean shape and continue to step 2.
Read more about this topic: Procrustes Analysis
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