# Satellite-Derived Bathymetry for Selected Shallow Maltee Coastal Zones
## 1 Introduction  
Bathymetry is the key parameter that provides the depth difference between the sea surface and the sea floor [1] and provides means of quantifying the depths of multiple water bodies including oceans, rivers, seas, streams, and lakes [2]. Furthermore, bathymetry encompasses a similar geospatial framework to land topography, embodying critical boundary conditions for oceanographic, geological, biological, and geophysical systems [3]. Accurate determination of the water depth has become crucial in understanding several global interaction processes which in turn influence a number of marine factors including, but not solely, the flow of sea water carrying heat, pollutants, nutrients, and salt [4]. High resolution bathymetric data are crucial for various purposes including monitoring underwater topography, generating nautical charts to aid in navigation, and gauging the movement of deposited sediment underwater [5, 6]. Additionally, in relation to ongoing worldwide effects on our environment, bathymetric information has become ever more important to understand the effect that climate change is inducing on the marine environment, to detect sea-level rise and underwater subsidence, and to notify scientists of any changes experienced by coastal morphodynamics [7]. Bathymetric information is paramount to help maintain and operate coastal zones. These transitional, dynamic, and rapidly changing regions between land and water incorporate significant economic, social, and biological value which experience various pressures resulting from both natural and anthropogenic processes [8, 9]. Understandingthe submerged topography helps in achieving a number of marine related applications, for instance, realistic hydrodynamic 3D modelling, exploration of submerged landscapes and archaeological sites, coastal climate assessments [10], and port and waterway dredging, as well as resource management [11]. Bathymetry is at the forefront of coastal modelling, and thus, the availability of comprehensive depth information at various temporal and spatial scales is fundamental [12]. Acoustically driven technologies and airborne laser techniques are amongst the most conventional methods used to conduct in situ bathymetric surveys. The two most widely adopted acoustic methods for vessel-based high-resolution mapping of coastal regions are Singlebeam (SBES) and Multibeam Echo Sounders (MBES) [13]. Sound navigation and ranging (Sonar) bathymetry techniques produce highly precise depth values in deeper waters. Despite that, acoustic techniques encounter difficulties and lose efficacy in shallower environments with depths measuring only a few tenths of a metre [14]. Moreover, there are certain remote and constantly changing coastal areas that cannot be reached by hydrographic vessels, leading to insufficient and outdated data in those particular locations [15]. Thus, under these circumstances, bathymetric data are gathered utilising airborne light detection and ranging (lidar) techniques [16]. While lidar bathymetric mapping has the potential to deliver precise results at a centimetre scale, it is constrained by spatial coverage limitations, restricted only to small regions as a result of technical barriers [17]. Regardless of the fact that these methods can generate precise water depth data, they are associated with substantial expenses and logistical challenges that often impede the collection of adequate coastal bathymetric data [18]. Presently, the collection of bathymetric data is being conducted via satellites equipped with optical sensors that utilise multi-spectral and hyper-spectral technology [19]. Multi-spectral satellites provide an alternative method for gathering shallow coastal water depth data by virtue of their wide swath width that enables them to provide information at different spatial and temporal scales in a cost-effective manner [20]. Furthermore, SDB holds significant value for researchers, particularly in remote regions of the world where in situ measurements are challenging or unfeasible [1].