Operationalization of Sar Polarized Data for Assessment of Coastal Erosion

This study introduces a new approach for operationalization of SAR polarized data on coastal erosion studies. Polarized TOPSAR and ERS-1 data are used for this purpose. ERS-1 data was acquired on the 8 August 1993 and polarized TOPSAR data was acquired on the 6 December 1996. A quasi-linear model and a new model based on the Canny algorithm were used to model shoreline changes. Digitized vector layers of shoreline change were used to examine the accuracy of the model results. This study shows that the results of the Canny algorithm has a good correlation with the results from the quasi-linear model. The Canny algorithm can successfully be used for automatic detection of shoreline change. In conclusion, the integration between the quasi-linear model and the Canny algorithm model enables further operationalization of SAR data for coastal erosion studies. 1.0 INTRODUCTION Coastal erosion studies from space are still in an early stage. Most studies that have been done by using remotely sensed data are restricted to the application of classical methods of shoreline identification based on digitizing and overlaying methods. These methods induce high rates of error and require a lot of time to process the data. In this process, the sum of thematic errors and digitizing errors account for the low accuracy of the interpretation results. This often results in inadequate solutions of the problems for coastal engineers and decision makers. For instance, Raj (1982); Mazlan et al., (1989), and Frighy et al., (1994) used different historical data of satellite imagery, aerial photography and topographic maps for coastal erosion studies. Most of these studies found an unrealistic high rate of erosion of more than 50 m/year. For instance, Frighy et al., (1995) found the rate of erosion in the Nile Delta to be –70.8 m/year. However, if this rate really had occurred, it would have caused the destruction of all the infrastructures, such as roads and bridges near the coastal waters. Furthermore, Frighy et al., (1995) stated that there is a significant relation between shoreline change, estimated from Landsat TM, aerial photography and ground surveys with a correlation coefficient (r) of 0.93. This can not be considered as a significant result, due to the fact that a significant statistical test such as ANOVA or the t-test have not been performed. In addition, the low resolution of the Landsat data (30 m) only justifies its use in coastal erosion studies with changes that are larger than this pixel size. As a matter of fact, the resolution of this sensor is unable to capture beach profiles at a width less than the pixel size (< 30m). The high resolution of SPOT PAN (10 m) and radar data such as from ERS-1 (12.5 m), Radarsat (12.5 m) and AIRSAR/TOPSAR (ca. 10 m) enables us to solve this type of problem. Maghed Marghany