Digital twin technologies integrate data, models, and physical entities. The paper explores technologies applied in the Urban Digital Twin (UDT) to support Urban regeneration (UR), with a case study of the small historic town of Draguć in Istria, Croatia, Europe. The subject of this research is to investigate and develop a digital twin model and to assess its usefulness in multidisciplinary applications for urban regeneration. The particularity of this scientific project lies in the application of multiple tools for 3D urban data collection and the modeling of this spatial information for its presentation and use, all aimed at spatial planning and sustainable urban development. The applied methods address a common challenge in projects aimed at establishing UDT. These methods encompass the integration of various technologies and tools (geodetic surveying, UAV photogrammetry, 3D laser scanning) for urban data collection, complemented by additional datasets from multiple sources. The results present an established UDT platform (environment) built upon the analyzed datasets relevant to urban regeneration. The urban matrix is displayed, together with buildings and their characteristics, cadastral data with ownership structure are analyzed, and a 3D city model has been generated. The proposed Urban Digital Twin model for the study area aims to facilitate, accelerate, and optimize urban regeneration, while also initiating integrated sustainable regeneration efforts for small historic towns.

The paper examines the potential use of low-cost LiDAR for cave surveying. Mobile mapping using LiDAR complements traditional speleological surveying using a polygonal traverse. These methods assist each other, with one serving as an independent control measurement for the other, ultimately resulting in a more accurate 3D model. The testing results show that achieving high accuracy and detailed cave representation is possible using open hardware and open-source software. Both spacious and well-indented cave sections and narrow passages barely passable by humans were successfully mapped. The surveying process is significantly faster than traditional cave mapping, as drawing cave sketches by hand is unnecessary, being the most time-consuming task on site. This paper also presents a procedure for automated ground plan generation and profile generation from 3D point clouds, further expediting and simplifying the work for speleologists using scanning systems. Also, it is confirmed that the results are reproducible and do not depend on the subjective interpretation of the cartographer, as is the case with traditional speleological drawings.