Improving CCD Performance by the Use of Local Fringe Frequencies

Abstract

Abstract-Coherent Change Detection (CCD) using multi-temporal Synthetic Aperture Radar (SAR) is one of the most important applications of remote sensing technology. With the advent of highresolution SAR images, CCD has received a lot of attention. In CCD, the interferometric coherence between two SAR images is evaluated and analyzed to detect surface changes. Unfortunately, the sample coherence estimator is biased, especially for low-coherence values. The consequence of this bias is the apparition of highly coherent pixels inside the changed area. Within this context, the detection performance will considerably degrade, particularly when using high resolution SAR data. In this paper, we propose a new CCD method based on cleaning of coherence inside changed areas, which is characterized by high Local Fringe Frequencies (LFF) values, followed by a space-averaged coherence method. According to the proposed method, the results obtained with Cosmo-SkyMed (CSK) SAR data show an enhancement of change detection performance of about 6% while preserving subtle changes.

Change Detection and Classification Using High Resolution SAR Interferometry

“…As shown in [8], a large number of samples N and a large window-size M are needed to detect the entire set of changes, which is obviously at the expense of the preservation of small changes. For that reason, another information source must be used to better analyze the coherence image.…”

“…Here, the coherence improvement is achieved using the LFF information as an additional change indicator, to clean the highly coherent pixels inside the changed areas that are also characterized by high LFF values [8]. area.…”

“…This method allows for the enhancement of the probability of detecting changes, but a large window size is still needed to detect the entire changes. The Local Fringe Frequencies (LFF), which is a measure of the interferometric phase variability, is successfully applied in [8] as an additional change indicator to clean the aberrant highly coherent pixels inside changed areas. The use of the LFF to enhance the coherence map permits an important improvement in change detection performance and offers the advantage of preserving the spatial resolution.…”

“…This aspect makes the CCD technique ideal for use in military and scientific applications such as border security and environmental monitoring. All these reasons lead to the development of new methods that enhance the change detection performance [4,8,9]. However, two main difficulties must be overcome in order to improve the analysis of CCD results.…”

“…The Coherent Change Detection (CCD) technique uses the coherence of a SAR image pair to quantify changes in the observed amplitude and phase of the image pixels. As the Interferometric SAR (InSAR) phase is sensitive to changes in the spatial distribution of scatterers within a resolution cell, the CCD technique that generally detects the low-coherence areas as ground changes [6,7] has the potential to detect centimeter changes that may remain undetected using only SAR intensity images (incoherent detection) [4,8].…”