Hypothesis Testing in Speckled Data with Stochastic Distances

TL;DR

This paper evaluates stochastic distances for hypothesis testing in speckled imagery modeled by the G0 distribution, finding that the triangular distance offers the best balance of size accuracy and power.

Contribution

It derives and compares eight stochastic distances for speckled data, recommending the triangular distance for hypothesis testing in SAR and similar imagery.

Findings

Triangular distance tests have sizes closest to theoretical expectations.

Arithmetic-geometric distances exhibit the highest test power.

Triangular distance provides a reliable and safe choice for hypothesis testing.

Abstract

Images obtained with coherent illumination, as is the case of sonar, ultrasound-B, laser and Synthetic Aperture Radar -- SAR, are affected by speckle noise which reduces the ability to extract information from the data. Specialized techniques are required to deal with such imagery, which has been modeled by the G0 distribution and under which regions with different degrees of roughness and mean brightness can be characterized by two parameters; a third parameter, the number of looks, is related to the overall signal-to-noise ratio. Assessing distances between samples is an important step in image analysis; they provide grounds of the separability and, therefore, of the performance of classification procedures. This work derives and compares eight stochastic distances and assesses the performance of hypothesis tests that employ them and maximum likelihood estimation. We conclude that tests based on the triangular distance have the closest empirical size to the theoretical one, while those based on the arithmetic-geometric distances have the best power. Since the power of tests based on the triangular distance is close to optimum, we conclude that the safest choice is using this distance for hypothesis testing, even when compared with classical distances as Kullback-Leibler and Bhattacharyya.