In a recent paper we described a method for assessing the accuracy of polygonal approximation algorithms. Here we develop several measures to assess the stability of such approximation algorithms under variations in their scale parameters. A monotonicity index is introduced that can be applied to analyse the change in the approximation error or the number of line segments against increasing scale. A consistency index quantifies the variation in results produced at the same scale by an algorithm (but with different input parameter values). Finally, the previously developed accuracy figure of merit is calculated and averaged over 21 test curves for different parameter values to obtain more reliable scores.
