Image texture is one of the key features used for the interpretation of radar facies in ground-penetrating radar (GPR) data. Establishing quantitative measures of texture is therefore a critical step in the effective development of advanced techniques for the interpretation of GPR images. This study presents the first effort to evaluate whether different measures of a GPR image capture the features of the data that, when coupled with a neural network classifier, are able to reproduce a human interpretation. The measures compared in this study are instantaneous amplitude and frequency, as well as the variance, covariance, Fourier-Mellin transform, R-transform, and principle components (PCs) determined for a window of radar data. A GPR section collected over the William River delta in Saskatchewan, Canada, is used for the analysis. We found that measures describing the local spatial structure of the GPR image (i.e., covariance, Fourier-Mellin, R-transform, and PCs) were able to reproduce human interpretations with greater than 93% accuracy. In contrast, classifications based on image variance and the instantaneous attributes agreed with the human interpretation less than 68% of the time. Among the textural measures that preserve spatial structure, we found that the best ones are insensitive to within facies variability while emphasizing differences between facies. For the specific case of the William River delta, the Fourier-Mellin transform, which retains information about the spatial correlation of reflections while remaining insensitive to their orientation, outperformed the other measures. Our work in describing radar texture provides an important first step in defining quantitative criteria that can be used to aid in the classification of radar data.