Design of semi-automatic algorithm for shoreline extraction using Synthetic Aperture Radar (SAR) images

Description

The coastal zones are one of the most rapidly changing environments in the world. The coast takes up a big portion of the Chilean territory, which results in one of the highest ratios of coastal kilometres to territory per km2 in the world. The capability for all-weather, day/night-imaging acquisition, short revisit periods and global coverage of Synthetic Aperture Radar (SAR) makes them a powerful remote sensing tool for mapping or maps updating. Over coastal areas, the nautical chart is one of the most usable sources of information for navigational, military, planning and coastal management purposes. One of the most important features in nautical charts is the coastline, which constitutes the physical boundaries of oceans, seas, straits and canals, etc. Digitizing a feature such as the coastline is a very tedious and time-consuming operation. The development of a semi-automatic algorithm to detect shoreline is a required task that has to be implemented in the process of nautical chart production in the Chilean Hydrographic and Oceanographic Service. Doing so would save a large amount of time in the process of coastline digitizing, which currently is achieved manually. Previous works have achieved good results in shoreline extraction. But, these works are less appropriate when applied to areas with high local environmental noise caused by the rough sea surface. After identifying the general steps governing the detection of shorelines in SAR images, this thesis develops a new technique to enhance land-water boundaries called the Multitemporal Segmentation Method. Also, the iterative application of windows to get rid of the noise over the sea surface is developed to achieve land-water separation. After detecting the coastline, the bias in the delineation is acceptable, reducing the offsets towards the sea that can result from the application of common filters. Depending on the application and the scale of the final product, analysis by the operator is still very important in this semiautomatic method. The extracted coastline requires a final examination. Also, the extracted coastline is referred to the in-situ water line; consequently it must be referred to the desired tidal datum.