Abstract: This article presents the performance of a new approach to determine the model order for the modified Prony method applied to swath acoustic mapping. Key requirements for any mapping application are depth determination accuracy and angular resolution. Depth determination accuracy is strictly related to angular accuracy and geometrical relations between receiver and sources of the backscattered signal. Angular resolution determines detection capabilities of targets laying on the seafloor. Performance of the proposed method, in terms of these two parameters, is tested against a simulated signal in a number of generic configurations, and compared to the results of other methods applied to the same signal.