What is Bathymetry?
Bathymetry refers to the study and mapping of underwater terrains. Just as topographic maps depict the elevation of land, bathymetric maps illustrate the depth and shape of underwater features such as seabeds, lakebeds, and riverbeds. Understanding these underwater landscapes is crucial for activities like navigation, coastal management, environmental monitoring, and offshore engineering.
What is Satellite-Derived Bathymetry?
Thanks to its remote sensing nature, Satellite-Derived Bathymetry (SDB) technology allows users access to shallow water insights using the satellite data at a lower cost compared to hydrographic survey campaigns and can be used for areas that are otherwise inaccessible or difficult to survey by other means.
Satellite Parameters
Spectral Resolution
Spectral resolution describes a sensor’s ability discriminate differences in radiation. The higher the number of bands, the narrower the range of wavelengths of each band, and the higher the spectral resolution of the satellite. Although SDB uses multispectral data (with 4 bands required for estimating SDB), higher spectral resolution data allows for better discrimination between different water constituents, such as chlorophyll, suspended sediments, and bottom materials. Depending on the water constituents and their spectral characteristics, the optimum bands can be selected to estimate the relative depths.
Spatial Resolution
The spatial resolution requirements depend on the bathymetry application. However, due to the optimal use of multispectral data for SDB and the availability of multispectral data with very high resolutions, SDB can be retrieved at different high resolutions, such as 30 cm (Pleiades Neo), 50 cm (Pleiades), or 1.5 m (SPOT), with the availability of pansharpened reflectance products.
Temporal Resolution
The temporal resolution of satellite sensors defines the capabilities of sensors to record the same place on Earth over a period of time. Multi temporal data approaches to SBD are especially helpful for filling in gaps caused by cloud cover, turbidity, breaking waves, and other episodic factors.
Applications of Satellite-Derived Bathymetry
Environmental Characterisation
With anthropogenic effects contributing to climate change, including beach erosion and loss of biodiversity, there is a greater need for accurate and up-to-date information on bathymetric data of shallow coastal regions. Scientists use bathymetry data to study the habitats of bottom-dwelling organisms, to determine where fish and other water life feed, live, and breed as well as to discover macrophytes growth at variable depth ranges. Temporal monitoring of SDB at local to global scale reveals geomorphological changes, sedimentation and erosion processes, and underwater formations.
Charting
SDB methods are useful in carrying out pre-survey plans particularly in areas where no prior survey has been carried out or in the case that the existing charts are doubtful or inaccessible. The use of SDB data for the identification of non-navigable shallow areas can be used by hydrographical officers. This data ensures the accurate navigation and safe route planning.
Coastal and Offshore Engineering
Coastal and offshore engineering includes the design, installation and asset integrity monitoring of marine and coastal structures. SDB and related information on seabed characterisation can be used to support the pre-installation of nearshore marine assets. During pre-installation SDB can provide reconnaissance bathymetry data for the planned construction site. Archival satellite imagery data provides engineers temporal and historical bathymetry analysis at regular intervals to understand the seafloor and structure dynamics. The temporal analysis also offers advantages for coastal engineering applications and post-installation monitoring, for example combining to overtime environmental impact, coastal resilience or beach replenishment studies, seabed mobility that might impact the assets.
Case Study - Crete, Greece
Benefits of Using Satellite-Derived Bathymetry
Using satellite technology for bathymetry offers several advantages:
Cost-Effective: Reduces the need for expensive vessel-based and drone surveys, especially in remote or difficult-to-access areas.
Large Coverage: Satellites can map vast areas quickly, making them ideal for regional studies.
Non-InvasiveEco-friendly: Avoids disturbance to sensitive marine environments Vessel-based surveys can disturb marine environments, but SDB avoids disturbances to sensitive marine ecosystems.
Rapid Data Collection: Provides timely information for urgent emergency projects or disaster response.
Revisitable: Satellites regularly revisit areas, enabling consistent monitoring and trend analysis.
Water Quality
Bathymetric data can be integrated with other water quality parameters (e.g., pH, dissolved oxygen, turbidity) to offer a holistic view of the aquatic environment. This integration deepens the understanding of how physical features affect chemical properties and the overall biological health of the ecosystem.
Conclusion
Satellite-Derived Bathymetry represents a significant advancement in how we study underwater landscapes. By leveraging remote sensing technologies, we can access detailed, cost-effective, and sustainable insights into aquatic environments. Whether you’re managing a coastal project or exploring new opportunities; this technology opens a world of possibilities.
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