HIGH-RESOLUTION DIGITAL TERRAIN MODEL FOR THE ITALIAN TERRITORY

High-resolution digital terrain models are essential for environmental planning and territorial analyses, and provide foundations for geomorphological and hydrological applications, including flood and landslide modelling and geo-hydrological hazard and risk assessments. In Italy, airborne LiDAR surveys have improved the representation of terrain morphology in the last decade, but their coverage is heterogeneous, as datasets originate from different local and regional institutions with different acquisition periods. Conversely, the national TINITALY 1.1 model provides a complete coverage at 10 m resolution, though with limited detail in low-relief areas. This study illustrates the HR-DTM-5m, a seamless 5 m-resolution digital terrain model for the entire Italian territory, obtained by integrating LiDAR-derived DTMs with TINITALY 1.1, through a reproducible workflow including harmonisation, regional mosaicking, re-sampling, vertical bias correction and smooth blending of adjacent datasets. The validation procedure was designed to reflect the purpose of the dataset, namely ensuring morphological consistency and hydrological reliability at national scale, rather than maximising point-scale accuracy. Results show negligible vertical bias, smooth transitions across dataset boundaries, improved slope representation in gentle terrains, and better alignment of extracted drainage networks with subtle topographic features. HR-DTM-5m provides a consistent national terrain reference for modelling flood dynamics and slope processes.