Stepwise Validation of Multibeam Echosounder Data Processing Using an Open-Source Processing Workflow: A Case Study in the Argolic Gulf (Greece)

Accurate hydrographic surveying in coastal environments requires not only high-resolution multibeam echosounder (MBES) measurements but also structured and reproducible data processing workflows that enable validation of applied corrections. This study presents a stepwise methodology for MBES data processing and quality assessment, focusing on the evaluation of successive correction stages and their impact on bathymetric products. The workflow is implemented using the open-source software GLOBE and demonstrated on MBES data acquired in the Argolic Gulf (Greece), provided by the Hellenic Navy Hydrographic Service (HNHS).

The Argolic Gulf is a semi-enclosed coastal basin with variable bathymetry, making it a suitable test case for assessing the influence of navigation, sound velocity, and tidal corrections. The dataset originates from a nearshore hydrographic survey conducted with a hull-mounted SeaBat 7125 multibeam echosounder system. Data delivered by the HNHS included raw multibeam soundings, associated navigation data, sound velocity profiles, and official tide information required for standard hydrographic post-processing. Processing of sound velocity profiles was carried out using DORIS, an open-source software package.

The proposed workflow consists of a sequence of correction steps, including navigation correction, sound velocity adjustment, tidal referencing, geometric transformations, and targeted filtering of outliers. Each step is evaluated independently through the generation of intermediate Digital Terrain Models (DTMs), enabling direct comparison of bathymetric surfaces before and after each correction. Stepwise validation is based on systematic map comparison. Intermediate DTMs generated in GLOBE, are imported into the open-source GIS environment QGIS, where thematic depth maps, bathymetric difference surfaces, and representative depth profiles along characteristic transects are produced. This combined map- and profile-based evaluation supports supervision and validation of applied corrections, facilitating the identification of systematic artefacts such as sound velocity–related curvature patterns, navigation-induced shifts, and localized swath-edge noise.

The stepwise comparison of intermediate bathymetric surfaces enables systematic validation and supervision of MBES corrections, demonstrating that individual correction effects can be assessed independently and that the reliability of the final bathymetric product can be evaluated prior to acceptance. The proposed workflow supports reproducible hydrographic surveying and contributes to improved reliability and interpretability of MBES-derived bathymetric surfaces in coastal and nearshore environments.