# A Hybrid Bio-Optical Transformation for Satellite Bathymetry Modeling Using Sentinel-2 Imagery
## 5 Conclusions  
The aim of the proposed hybrid bio-optical transformation (HBT) model is the use of minimum manpower, along with low-cost chart data in order to extract SDB from free-of-charge multispectral imagery. The preliminary encouraging results indicate the potential of the HBT method to be further extended into future trials over areas of high importance for navigation safety, but also in other marine applications, such as coastal management, and environmental and climate change monitoring. Given the scientific and commercial interest that SDB has been attracting, the proposed HBT bathymetric model may contribute to the Marine Spatial Data Infrastructure (MSDI), according to the recommendations and guidelines of the IHO (International Hydrographic Organization, [11]) and the EMSA (European Maritime Safety Agency, [29]).  
The preliminary results show that the spectral attributes of seabed benthic communities are related directly with the spectral characteristics of physical and optical properties of the supernatants within the water column. In addition, the seabed classification can feasibly be accomplished by analyzing the bio-optical parameters. Hence, it is possible to link temporally and spatially the seawater optical properties with other marine physical features, such as seabed sediment type and/or bathymetry in the area of interest. The conducted tests showed that HBT extracted bathymetry contributes to rapid depth modeling and promises to address the difficulties currently encountered in the rapid collection of bathymetric data. In this framework, there is a need to further test the hybrid bio-optical transform (HBT) model by applying optimization techniques during the model calibration/training phase, in combination with machine learning classification techniques or artificial intelligence techniques.  
HBT aims to address the difficulties currently encountered in the rapid collection of bathymetric data, when priority is given to the use of limited human and technical resources, as well as to the short completion, production, and updating of existing nautical charts. In order to develop practical rules of thumb for the updating of nautical charts, according to the relevant specifications of the IHO, there is a clear need to perform further trial tests in other coastal areas, including error analysis, various satellite sensors, and comparisons against in situ data collected by modern systems, such as Lidar, or multibeam sonar. Future plans include such trials and the comparison of their outcome with the international standards of IHO.  
[PERSON] conceived of the presented Bathymetric Transformation Modelling, performed the computations and presents the results; [PERSON] evaluated the analytical method and supervised the findings of this work; [PERSON] encouraged [PERSON] to continue the experiments and contributed to the interpretation of the results focusing on the aspects of the Safety of Navigation; [PERSON] supervised the findings of this work and contributed to the editing of the manuscript; All authors discussed the results and contributed to the final manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.