On the Detection of Peaks and Valleys Using the Local Descriptors Method

In this correspondence it is demonstrated that the derivative of the angle with respect to an arbitrary independent parameter cannot in general be used to find peaks and valleys of a shape. It is then shown, using concepts from differential geometry, that curvature corresponds to the derivative of the angle with respect to an independent variable if and only if the angle is deflned as a single variable. It is further shown that peaks and valleys detected using curvature as a criterion are insufficient to completely describe a shape.