Multiscale Digital Survey and HBIM-GIS Integration for the Conservation of the Kasbah of Mehdya (Morocco)

Abstract. This paper presents the development and validation of a multiscale digital workflow to document and support the conservation of the Kasbah of Mehdya, a coastal fortified complex located at the mouth of the Sebou River (northern Morocco). Data acquisition integrates UAV survey (photogrammetry and aerial LiDAR) to capture site morphology and topography, SLAM-based mobile mapping for rapid point-cloud acquisition in GPS-denied or partially constrained areas, and high-resolution terrestrial imagery, including spherical panoramas, to enhance material and decay interpretation. The datasets are processed, filtered, and aligned to generate georeferenced orthophotos and dense point clouds that feed a scan-to-HBIM pipeline. HBIM models are structured as semantic repositories of construction phases (12th–17th centuries), traditional materials, and mapped decay patterns, and are exported through interoperable standards (e.g., IFC) to enable integration within a GIS geodatabase. The resulting HBIM–GIS environment supports multiscale spatial queries, correlation analyses between observed pathologies and key coastal environmental drivers (e.g., sea-salt aerosol exposure and vegetation colonisation), and the progressive validation and refinement of pre-existing territorial datasets through “as-built” survey data. Beyond format-level interoperability, the approach treats geo-referencing consistency and data reliability as prerequisites for a transferable heritage digital twin bridging architectural and territorial scales. Finally, it lays the groundwork for participatory dissemination through a WebGIS interface and immersive visualisation tools to support evidence-based, time-sensitive conservation strategies.