Extended Reality Interfaces for a Geospatial Digital Twin: Immersive Visualization and Collaborative Decision Support for District-Scale Hydrogeological Risk Governance

Geospatial Digital Twins (GDTs) integrate authoritative spatial data, Earth Observation products, and near-real-time sensing streams, yet their use in public-sector territorial governance remains screen-based. This article documents the design, implementation, verification, and deployment of Mixed Reality (MR) and Virtual Reality (VR) interfaces connected to the GDT of the Central Apennine River Basin District Authority (AUBAC), whose jurisdiction extends over a 42,275 km2 district spanning seven central Italian regions. The study combined design science research with an operational case study, progressing through requirements elicitation, iterative prototyping, verification, acceptance, and institutional use. The MR application supports co-located collaborative exploration of governed territorial data, while the VR application enables district-scale navigation using Google Photorealistic 3D Tiles and access to georeferenced Google Street View panoramas. Observations indicate that XR is used selectively for three-dimensional morphological interpretation, shared spatial context, and immersive site familiarization, whereas WebGIS supports routine analysis, complex queries, and time-series inspection. This allocation reflects operational practice rather than a measured comparison of interface performance. The study provides a transferable reference for integrating XR into large-scale GDT workflows and identifies constraints concerning setup, connectivity, third-party services, lifecycle management, comfort, accessibility, and maintenance. The case supports climate-resilient territorial governance and SDGs 11 and 13.