In certain areas of the world with large tidal ranges, rain and wind can cause the path of channels and estuaries to shift dramatically. Lifeboat rescue services must navigate through these areas in spite of the dangers it can entail. This work investigates the alternatives to provide regular mapping of the seabed, enabling these teams to reach casualties without becoming casualties themselves. Underwater Vehicles, SONAR systems and Unmanned Aerial Vehicles are all considered viable options but satellites equipped with synthetic aperture radar are proven to be the most advantageous. To map the path of the estuary, images must be taken during low tide, therefore, data availability is assessed by studying the revisit time and matching this to the tidal status of the area of interest. Different satellite options are examined, including commercial and non-commercial but a specific focus is given to Sentinel-1 due to its free accessibility. The periodicity of the satellite coupled with the tidal behaviour causes intervals during the month where no usable images can be taken. The maximum number of days between consecutive useful images is found to be 12, with an average of 6 useful images per month. The periods where these intervals happen are also identified. Therefore, to meet the user needs, an auxiliary system must be implemented to assist the satellite and increase the number of useful images taken per month. The area of interest of this study is the Solway Firth due to its fast tidal movements and ranges.
Across the world, many coastal tidal regions are unsafe to navigate due to shifting mud and sand pushed by water currents. Ability to regularly map the current location of a channel will aid safe passage for commercial, leisure and rescue craft. This work investigates the use of synthetic aperture radar data derived from satellites to provide accurate mapping of moving channels in coastal regions. As images must be collected at low tide, data availability is assessed considering the relationship between the orbital motion of the satellites and the tides. Change detection methods are applied to suitable images to map changes in the location of navigable channels. Pixels that undergo similar changes over time (e.g. from water covered to exposed sand) are grouped together by examining the principal component of the covariance matrix, for a vector composed of pixel values from the same location at different times. The Solway Firth in Great Britain is selected as a trial site as it is exposed to some of Europe’s fastest tidal movements and ranges, and hence is one of Great Britain’s most treacherous stretches of coastline.
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