Fast and accurate GCPS selection scheme for SAR image registration based on an improved Trajkovic corner detector

There is a wide range of corner detector available such as the Moravec, Forstner, Harris and Trajkovic detectors. Beside the most commonly used Harris detector, the Trajkovic detector was found to have a slightly lower detection accuracy, but at a much faster computational rate, which is more favorable when it comes to high speed applications. However, the Trajkovic cornerness measure was defined using intensity differencing for optical imagery, hence it is not suitable for synthetic aperture radar (SAR) imagery, which suffers from multiplicative speckle noise. Moreover, the Trajkovic detector has a tendency to respond too readily to diagonal edges, thus it only shows good results to certain types of corners. This paper introduces a novel ground control points (GCPs) scheme to improve the speed and accuracy for SAR image registration. The scheme involves a reformulation of the Trajkovic cornerness measure in the form of a SAR intensity ratio, a hybrid scheme of Trajkovic operators for higher processing speed, and a corner refinement stage for better detection accuracy. Experiments carried out on a pair of multi-date RadarSat-2 images had shown a significant higher accuracy than in the case of the original Trajkovic detector, while performing much faster compared to the Harris detector.