A Survey on SAR Imagery Utilizing Different Image Procsessing Techniques and Proposed System on Flood Water Mapping

Abstract

In a time of need and uncertainty for people, the government and humanitarian organizations must be able to accurately measure the flood extent in the near real-time to strengthen early warning systems and assess the risk. Ground measures are spatially limited, costly to maintain, and accurate only in special circumstances. The government and humanitarian organizations must be able to accurately measure the flood extent in the near real-time without expensive remote sensing systems. This is where high-precision satellite imagery can complement ground measurements by supplementing imagery with hydrological information. Rain and stream gauging stations, however, only measure the water height and have limitations by geographic placement and cost of maintenance. High- resolution satellite imagery has strengthened monitoring by providing data in otherwise inaccessible areas at frequent time intervals. In particular, sensors operating in the microwave portion of the spectrum can operate at low signal-to-noise ratios over a greater range of frequencies than sensors operating in other portions of the electromagnetic spectrum. This allows a single sensor array to provide greater bandwidth and spectral resolution, which is important for distinguishing between water and other objects in images containing both water and other objects, particularly where subtle differences, in contrast, exist between water and other objects. High-resolution synthetic-aperture radar (SAR) imaging has strengthened monitoring systems by providing data also in inaccessible areas at frequent time intervals. It operates in the microwave band of electromagnetic spectrum, and is able to capture images through clouds, precipitation, vegetation, and smoke, making it beneficial for flood detection. A high-resolution synthetic-aperture radar (SAR) imaging system uses microwave frequencies to penetrate clouds and other interference that may hinder traditional communication systems. It creates extremely accurate images of the ground just below the surface, allowing for detailed monitoring at any time and from nearly any location. The Sentinel-1 mission comprises two satellites, Sentinel-1A and Sentinel-1B, performing C-band synthetic-aperture radar (SAR) imaging. The primary difference between SAR systems and optical sensors is that SAR systems operate in the microwave band, where long waves can penetrate through clouds, vegetation, fog, rain showers, and snow.