Giorgio Paolo Maria Vassena

In Indoor Mobile Mapping Systems (iMMS) the trajectory estimation is implemented by the SLAM (Simultaneous Localization and Mapping) algorithm. By assuming a fixed environment surrounding the instrument, the algorithm relies on stable geometries to establish the trajectory. Drift effects represent the main source for errors and affect the trajectory estimation. These effects can be magnified in feature-deficient or degenerate environments, where the variation of geometrical elements can be minimal, as in the case of tunnels. In this context, difficult environments such as tunnels are suitable for the implementation of alternative algorithms for the trajectory estimation. Considering this kind of scenario, the contribution has the twofold objective of evaluating the results of two trajectory estimation methods, in terms of trajectory drift, with reference to an indoor SLAM-based MMS, and to establish a repeatable methodology to do so. A novel algorithm for the trajectory estimation, not just relying on geometrical SLAM algorithm, but also taking advantage of reflectance images coming from LiDAR sensors mounted on the system, is considered. The case study is a 200 m long branch of a motor-way tunnel, with a diameter of 15 m. The test is further subdivided by computing all trajectories with different constraining strategies, first without any constraints, then considering global optimisation, loop closure and static control scans, to replicate typical realistic scenarios in tunnel mapping. The results of this work highlight how the novel reflectance-aided SLAM algorithm is beneficial in terms of drift reduction in the estimated trajectories.

Ant3D is a fisheye multi‑camera system for 3D mapping in confined environments, designed and refined over a seven‑year period. This paper has two aims: to present the latest tests reflecting recent system developments and to summarize the design journey and milestones. We compare three successive surveys tests conducted in the same challenging test site: meandering masonry interiors and rock‑cut passages within San Vigilio Castle (Bergamo, Italy). The 2018 test used a low‑cost GoPro multi‑camera rig; the 2020 test used Ant3D v1, a custom prototype improved based on the previous experiences; the 2025 test employed the first industrialized Atom‑Ant3D, integrating SLAM‑based pose estimation, pose‑graph optimization, and SLAM‑aided SfM to accelerate processing. The comparison considers reconstruction drift against a TLS ground‑truth point cloud and processing times. Results show Ant3D v1 achieves high accuracy (max deviation ~3cm) but required extensive processing times (~20h), Atom‑Ant3D offers major time savings (~4.5h) with moderate accuracy trade‑offs, and the GoPro rig performs worst. The discussion outlines design and processing guidelines for reliable, fast mapping of narrow spaces.

Indoor Mobile Mapping Systems (iMMS) are based on trajectory estimation through the implementation of the SLAM (Simultaneous Localization and Mapping) algorithm. The algorithm has the limitation of requiring the environment being surveyed to have well-varied geometry. Indeed, the SLAM algorithm, by assuming a stable environment, tracks changes in the device’s position relative to a landscape of fixed elements and geometries surrounding it. iMMS can operate in outdoor environments and in mixed indoor/outdoor situations. It has been established that SLAM systems are affected by significant geometric drift effects in trajectory estimation. One commonly adopted strategy is to enforce that the surveyed trajectories are closed. Another approach involves introducing constraints in the form of control scans or control points. In particular, control vertices are typically constituted of coordinate points physically measured in the field by the operator, by placing the tip of a measuring pole on them. If in indoor applications, control vertices are generally measured with a total station, in outdoor applications they can also be measured with GNSS measurement campaign. For this reason, it is increasingly necessary to develop easy and accurate integration between iMMS and GNSS receivers to enhance the efficiency of SLAM-based mobile systems in outdoor environments, allowing high-throughput surveys. This article presents the results of such integration, providing guidelines on the most efficient operational methods for introducing these constraints. The contribution details the procedures for hardware design, electronic integration and the development of an application that applies a rigorous cartographic approach, within the compatible limits of the available technologies.

This paper presents a comparative evaluation of six cloud-based platforms including ArcGIS Online, Cintoo, Flai, Pointly, Cesium ion, and Atis.cloud for historic garden conservation, applied to two contrasting case studies: the complex, large-scale Naxos Archaeological Park and the compact, formal Villa Burba in Italy. Results show that Cesium ion and Cintoo performed strongly in point cloud visualization, with Cesium ion offering responsive large-scale rendering and Cintoo supporting high-precision geometry and version control. Flai demonstrated effective AI-driven element classification, particularly in heterogeneous landscapes, while Pointly required manual refinement and showed limited adaptability to organic features. ArcGIS Online excelled in stakeholder usability and layered documentation but lacked native 3D analytics. Collaborative functions were best addressed by Cintoo and Atis.cloud. Temporal functionality, such as phase comparison or seasonal tracking, remained limited, with no platform providing fully integrated support. The study highlights the fragmented nature of current solutions and argues for a modular, garden-oriented CDE model, integrating semantic intelligence, temporal awareness, and stakeholder-specific interfaces to support adaptive, sustainability-sensitive historic garden conservation in the cloud.

This paper discusses the utilization of a wearable Mobile Mapping System (MMS) (Gexcel HERON MS TWIN Color) for an extensive 3D survey of the Doge’s Palace in Venice, highlighting both the potential and the challenges of employing such technology in architectural contexts to achieve architectural accuracy standards. In under seven hours, a trajectory over 17 km was documented, resulting in 101 scan pathways and over 30 billion data points. To attain the necessary architectural precision (1–5 cm), the MMS was integrated with static laser scans utilized as Ground Control Scans (GCSs), and data processing was performed using Heron Desktop, involving extensive parameter calibration and manual trajectory optimization to reduce SLAM-induced drift and misalignment. The study identifies significant issues such as the evaluation and mitigation of drift errors, as well as extensive data management, providing practical solutions and underscoring the essential role of human experience in the processing phase. Although wear-able MMS demonstrates significant potential for swift, extensive architecture documenting, the necessity for hybrid methodologies and meticulous preparation is crucial to achieving the elevated accuracy requirements mandated in cultural heritage contexts.

Technological development has strongly impacted all processes related to the design, construction, and management of real estate assets. In fact, the introduction of the BIM approach has required the application of three-dimensional survey technologies, and in particular the use of LiDAR instruments, both in their static (TLS—terrestrial laser scanner) and dynamic (iMMS—indoor mobile mapping system) implementations. Operators and developers of LiDAR technologies, for the implementation of scan-to-BIM procedures, initially placed particular care on the 3D surveying accuracy obtainable from such tools. The incorporation of RGB sensors into these instruments has progressively expanded LiDAR-based applications from essential topographic surveying to geospatial applications, where the emphasis is no longer on the accurate three-dimensional reconstruction of buildings but on the capability to create three-dimensional image-based visualizations, such as virtual tours, which allow the recognition of assets located in every area of the buildings. Although much has been written about obtaining the best possible accuracy for extensive asset surveying of large-scale building complexes using iMMS systems, it is now essential to develop and define suitable procedures for controlling such kinds of surveying, targeted at specific geospatial applications. We especially address the design, field acquisition, quality control, and mass data management techniques that might be used in such complex environments. This work aims to contribute by defining the technical specifications for the implementation of geospatial mapping of vast asset survey activities involving significant building sites utilizing iMMS instrumentation. Three-dimensional models can also facilitate virtual tours, enable local measurements inside rooms, and particularly support the subsequent integration of self-locating image-based technologies that can efficiently perform field updates of surveyed databases.

Technological development has strongly impacted all processes related to the design, construction, and management of real estate assets. In fact, the introduction of design procedures using a BIM approach has required the application of three-dimensional survey technologies, and in particular the use of LiDAR instruments, both in its static (TLS – Terrestrial Laser Scanner) and dynamic (iMMS – indoor Mobile Mapping System) implementations. Operators and developers of LiDAR technologies, for the implementation of scan-to-BIM procedures, initially placed special care and attention on the 3D sensing accuracies obtainable from such tools. The incorporation of RGB colorimetric data into these instruments has progressively expanded LiDAR-based applications from essential topographic surveying to geospatial applications, where the emphasis is no longer on accurate three-dimensional reconstruction of buildings, but on the capability to create three-dimensional images based visualizations, as Virtual Tours, which allow to recognize the assets located in every area of the buildings. Although much has been written about obtaining the best possible accuracies for extensive asset surveying of large-scale building complexes using iMMS systems, it is now essential to develop and define suitable procedures controlling such kinds of surveying, targeted at specifically geospatial applications. We especially address the design, field acquisition, quality control, and mass data management techniques that might be used in such complex environments. This work attempts to contribute in this sense by defining the technical specifications for the implementation of geospatial mapping of vast asset survey activities involving significant building sites utilizing iMMS instrumentation. Three-dimensional models can also facilitate virtual tours, enable local measurements inside rooms, and particularly support the subsequent integration of self-locating pictures based technologies, that can efficiently perform field updates of surveyed databases.

This paper presents a comprehensive scoping review of the application of 3D digital technologies in the documentation, conservation, and management of historic gardens and related cultural heritage. By analyzing a curated selection of literature, this study assessed the current state of research, highlighting trends in publications, the geographic distribution of contributors, and the key technologies employed. Using bibliometric methods and visualization tools, followed by a case study review, this review identified significant research hotspots and technical methodologies, particularly focusing on advanced techniques such as mobile laser scanning, UAV photogrammetry, and point cloud processing and their relationships with end users. The findings emphasize the importance of integrating multiple technologies to capture the diverse elements of historic gardens, including architectural features, vegetation, and topography. This review also underscores the significance of dynamic landscapes facing challenges posed by environmental degradation and urban development pressures. Moreover, it discusses the limitations of existing research and outlines future opportunities, such as the development of 4D documentation systems and the incorporation of AI for improving heritage management. This paper concludes by recommending interdisciplinary collaboration and public engagement to enhance the accessibility, understanding, and sustainable management of historic gardens through innovative technological applications.

This paper presents a comprehensive scoping review of the application of 3D digital technologies in the documentation, conservation, and management of historic gardens and related cultural heritage. By analyzing a curated selection of literature, the study assesses the current state of research, highlighting trends in publication, geographic distribution of contributors, and the key technologies employed. Using bibliometric methods and visualization tools, followed by case study review, the review identifies significant research hotspots, technical methodologies, particularly focusing on advanced techniques such as mobile laser scanning, UAV photogrammetry, point cloud processing, and their relationships with end users. The findings emphasize the importance of integrating multiple technologies to capture the diverse elements of historic gardens, including architectural features, vegetation, and topography. The review also underscores the significance of dynamic landscapes facing challenges posed by environmental degradation and urban development pressures. Moreover, it discusses the limitations of existing research and outlines future opportunities, such as the development of 4D documentation systems and the incorporation of AI for improving heritage management. The paper concludes by recommending interdisciplinary collaboration and public engagement to enhance the accessibility, understanding, and sustainable management of historic gardens through innovative technological applications.

This paper presents an effective and low-cost approach for the digitisation of a Roman bronze head exhibited at the Santa Giulia Museum in Brescia using close-range photogrammetry. The artefact posed significant challenges due to its dark, reflective exterior surface and its hollow interior, accessible only through an 8 cm neck opening. The digitisation had two main objectives: (1) to support restoration activities by accurately measuring the thickness of the bronze cast, and (2) to enhance the artefact's dissemination by producing a web-optimised digital replica.Special emphasis was placed on the survey of the internal surface, achieved using a custom-designed camera probe equipped with a 5 megapixels RGB global shutter camera and LED ring lights. With this setup it was possible to effectively captured the inner geometry using low-cost tools. The internal dataset was connected with the exterior dataset, acquired by a regular DSLR and turntable setup supported by cross-polarization.The processing workflow involved generating a high-resolution mesh model (~80M faces) and computing the cast's thickness using two methods: the M3C2 algorithm and the Shrinking Sphere algorithm, which provided consistent results. Additionally, an optimised low-poly version of the model was created for web sharing. This study highlights the potential of low-cost tailored photogrammetric solutions/workflows to address the complexities of digitising intricate museum artefacts.