Analysis of Four Polar Shape Descriptors Properties in an Exemplary Application

The paper presents the results of a comparison of four shape representation techniques that use the transformation of the points from Cartesian to polar coordinates. An exemplary application was selected — the recognition of characters extracted from polish car license plates. The main goal was the selection of the best polar shape descriptor basing on the experiments performed as well as the discussion on the application of the algorithms based on polar transform in the mentioned problem. The results of the experiment presented in the paper indicate that amongst used methods the Point Distance Histogram (PDH) works the best. The results achieved using the UNL and UNL-Fourier transforms are worse, yet still acceptable.