Use of ERS-1 SAR Data for Some Marine Applcations in Malaysia
Mohd Ibrahim Sensi Mohd, Samsudin Ahmad & Khor Soong Wei
Centre For Remote Sensing,
Faculty of Geoinformation Science and Engineering
Univerisiti Teknologi Malaysia,
Locked Bag 791, 80990 Johor Bahru, Malaysia
Tel : (07)-5502880 Fax : (6 07) 5566163
E-mail : mism@fksg.utm.my
Abstract
Radar remoter sensing has good potentials for application in areas that are prone to cloud cover especially in the tropics. Multi-temporal ERS-1 Synthetic Aperture Radar (SAR) data provide a useful tool for studying the ever-changing conditions and phenomenon in the sea. This paper reports on the results of a study that has been carried out under the EC-ASEAN ERS-1 project to derive some information in the marine environment from the ERS-1 SAR data. In the study, the data were processed to obtain ocean wave spectra in order to derive information about ocean wavelength and direction using the 2-D Fast Fourier Transform. A radar bathymetry model was also used to assess a number of maritime features potentially caused by topography of the sea bottom. The contrast profile produced by the model were compared to profile extracted from the ERS-1 images. Digital image processing was also carried out by using the PCI EASI/PACE and Ergo Vista software for visual interpretations of oil slicks, ship locations, ship wakes and some coastal features such as river outflow and fronts. The results of the study show that ERS-1 SAR data has great potential for applications in the Malaysia coastal zone.
Introduction
For applications in the marine environment, multitemporal ERS-1 SAR data provide a useful tools for studying the ever-changing conditions and phenomenon in the area. For radar bands in Spaceborne SAR systems the microwave radiation is not affected by the atmosphere and does not penetrate into the water. Therefore, all signature on SAR images are due to variations in the radar backscatter intensity from the water surface. Two test areas were selected, one area stretches from Kuala Terengganu to Dungun on the north-east coast of Peninsular Malaysia, and one near Kuala Baram on the north-west coast of Sarawak (Figure 1). Both areas are characterized by large outflowing river and are affected by coastal erosion and accretion during the monsoon season. In this paper, some of the results obtained in the MAL-2 EC-ASEAN ERS-1 Radar Remote Sensing Project are reported.
Bathymetry Signature Model
In the study, the radar bathymetry model implemented at TNO was used to assess a number of maritime features in the image potentially caused by topography of the sea bottom. This model is based on the action balance equation, weak hydrodynamic interaction theory and Bragg scattering (Vogelzang, 1989). The model which is suitable for shallow waters was run using estimated bathymetric profiles based on available hydrographic charts, wind, current velocities and directions at the time of ERS-1 imaging. The contrast profiles produced by the model were compared to profiles extracted from the ERS-1 images. The results are shown in figure 2(a), 2(b) and 2(c).
Figure 1: Map of the MAL-2 study area.
Figure 2(a) : Sea bottom profile and marine information in the study area.
Figure 2 (b) : Radar contrast derived from the model.
Figure 2 (c ) : Profile from ERS-1 data.
