The study of coastal and in general transitional waters is a vital research field in marine science. This is enforced by the fact that coasts provide high quality resources and opportunities that are able to sustain human societies. Therefore it is an increasing need to record and monitor the state of land-water boundaries and their sub-sections in order to have a clearer image regarding how they evolve through time.
The area of our specialization is in shallow seabed imaging and mapping focusing primarily on shallow coastal habitats. The main habitats of shallow ecosystems include,
• Submerged Aquatic Vegetation, seaweed
• coral reefs,
• hard substratum,
• rocky bottom,
• macro-algae beds
• unconsolidated sediments.
These areas have been recognized internationally as protected or to-be-protected environments, due to their significance in marine biodiversity and coastal protection. For example, hard substratum offers a great opportunity for colonization by a variety of benthic organisms that require to be attached. On the other hand sedimentary bottom is susceptible to hydrodynamic activity that carves bedforms and usually sustains sea grass meadows that play fundamental role in mitigation of coastal erosion processes.
These are only a small proportion of the shallow ecosystems functions. Consequently local and regional communities that live by the shoreline have recognized that successful management of shallow coastal habitats is greatly depended on accurate mapping. At this point digital cartography has been engaged for providing valuable data regarding the spatio-temporal expression of submerged geomorphological features for engineering and/or conservation purposes. The instrumentation that has been utilized so far for seafloor imaging is expressed in the table below. However mapping of shallow areas has become complicated and demanding issue in many cases. Main facts that cause problems in systematic observation of shallow water zones include:
• remote location,
• non-solid terrain in their proximity,
• small depth that endangers boat surveying
• expensive aerial/satellite data
• temporally unavailable datasets
• poor spatial resolution.
The shallow-transitional character of coastal boundaries is responsible for most mapping difficulties with sonar based instrumentation. The most significant restriction is due to the minimum operational depth for vessel safe operations. Moreover, in some circumstances application of sonar in extreme shallow water makes them more susceptible to noise resulting in obscured data and ambiguous interpretations. At the same time, shallow character of coastal waters favours new approaches that need to be developed for coastal seabed observation. One of these approaches is being analysed below in “Photogrammetry” section.