PORTS4.0-2023 "IDEAS" - I-4.75

Ports 4.0 is a flagship innovation funding initiative launched by the Spanish national port authority Puertos del Estado together with the regional port authorities. Its main objective is to attract, support, and accelerate entrepreneurial talent (startups, spin-offs, and intrapreneurs) within the Spanish logistics and port ecosystem in order to drive digital transformation, sustainability, competitiveness, safety, and efficiency in line with the principles of Industry 4.0.

The IDEAS line supports early-stage technological concepts at Technology Readiness Levels (TRL) 1–2, helping them evolve into initial proof-of-concept demonstrations (TRL 3). Spascat was selected with project I-4.75 “GAROTES”, in which the theoretical feasibility of a network of IoT buoys was explored to be combined with Earth Observation data in order to continuously obtain bathymetry in the surrounding areas of the Port of Barcelona. The objective was to validate the technical feasibility and demonstrate readiness for the next stages of innovation over a six-month period.

The proposed concept is a multi-domain system that combines satellite data with local depth measurements provided by buoys equipped with depth sensors, GNSS Galileo positioning, and IoT communications. This combination would allow calibration of Satellite Derived Bathymetry (SDB) models and the generation of depth maps with higher spatial and temporal resolution than traditional bathymetric survey campaigns.

To demonstrate the scientific feasibility of the concept within the framework of the IDEAS programme, the work was structured into three main phases. First, the necessary data were collected and prepared, including historical bathymetry datasets from the Port of Barcelona as well as additional datasets from coastal areas of the Barcelona Metropolitan Area (AMB).

In a second phase, Sentinel-2 satellite imagery from the European Copernicus programme was processed, selecting images coincident with the dates of the bathymetric campaigns. From these images, the main spectral bands and several derived indices commonly used in depth estimation were extracted. This dataset was then used to develop and compare different satellite-derived bathymetry models, including both empirical models based on spectral relationships and machine learning (ML) models capable of capturing non-linear relationships between reflectance and water depth.

Finally, during the validation phase, different buoy deployment scenarios were simulated to determine the minimum number of calibration points required to maintain reliable bathymetry estimates. This simulation used the real bathymetry datasets as “ground truth”, selecting subsets of points representing potential buoy locations and evaluating to what extent they allowed reconstruction of the original depth map.

The proof-of-concept results indicate that the developed models perform well at depths of up to approximately −15 m, which corresponds to the range where satellite-derived bathymetry is generally reliable. In deeper areas or zones with very steep slopes (such as some parts of the port), accuracy decreases, mainly due to the spatial resolution of the available satellite imagery. It was also observed that model performance improves significantly when a sufficient number of calibration points distributed across the depth range of interest is available.

The study estimates that, using buoys with an operational radius of approximately 20–25 m, it would be possible to achieve calibration coverage of around 1.5% of the area of interest, corresponding to a density of approximately 8 to 12 buoys per km², provided they are homogeneously distributed. These results indicate that the GAROTES concept is technically feasible and can provide a solid basis for the continuous generation of bathymetric maps through the fusion of satellite data and in-situ sensors.

With this proof of concept, a Technology Readiness Level of TRL 3 has been achieved, corresponding to analytical and experimental validation of the key system functions. The next steps will involve the development and deployment of real IoT buoy prototypes in controlled maritime environments, with the objective of experimentally validating the system’s performance and progressing towards subsequent stages of technological development.