Convolutional neural networks (CNNs) are state-of-the-art techniques for image classification; however, CNNs require an extensive amount of training data to achieve high accuracy. This demand presents a challenge because the existing amount of measured synthetic aperture radar (SAR) data is typically limited to just a few examples and does not account for articulations, clutter, and other target or scene variability. Therefore, this research aimed to assess the feasibility of combining synthetic and measured SAR images to produce a classification network that is robust to operating conditions not present in measured data and that may adapt to new targets without necessarily training on measured SAR images. A network adapted from the CIFAR-10 LeNet architecture in MATLAB Convolutional Neural Network (MatConvNet) was first trained on a database of multiple synthetic Moving and Stationary Target Acquisition and Recognition (MSTAR) targets. After the network classified with almost perfect accuracy, the synthetic data was replaced with corresponding measured data. Only the first layer of filters was permitted to change in order to create a translation layer between synthetic and measured data. The low error rate of this experiment demonstrates that diverse clutter and target types not represented in measured training data may be introduced in synthetic training data and later recognized in measured test data.

Date Published: 27 April 2018
PDF: 10 pages
Proc. SPIE 10647, Algorithms for Synthetic Aperture Radar Imagery XXV, 106470A (27 April 2018); doi: 10.1117/12.2304568

Published in SPIE Proceedings Vol. 10647:
Algorithms for Synthetic Aperture Radar Imagery XXV
Edmund Zelnio; Frederick D. Garber, Editor(s)