High-definition shoreline digital twin from UAV-LiDAR-MBES fusion and XR-optimised 3D modelling

Understanding and monitoring the land-water interface is critical for navigation safety, shoreline management, and environmental protection in inland waters, yet its consistent digital representation remains challenging because terrestrial and submerged domains are commonly surveyed and analysed separately. This study presents an integrated workflow for constructing a high-definition shoreline geospatial twin from multi-sensor data within a unified RTK-referenced geodetic framework. Centimetre-scale topographic information from UAV photogrammetry and airborne LiDAR is fused with multibeam bathymetry to generate a spatially coherent 3D model of the land-water continuum. The workflow combines field calibration, harmonised horizontal and vertical referencing, topology-preserving surface reconstruction, mesh optimisation, and export to interoperable 3D formats for real-time GIS and XR use. A case study from the Masurian Lake District (Poland) demonstrates sub-decimetre geometric coherence across terrestrial and submerged zones. The study moves beyond static 3D shoreline representation toward an immersive and updateable geospatial twin for analytical exploration and navigation-oriented decision support. A virtual reality module supports exploration, planning, and training, while an augmented reality module enables in situ visualisation of shoreline and bathymetric features for hazard awareness. The framework provides a reproducible basis for inland-water navigation, environmental monitoring, and digital-earth applications.