Application of micro-CT and SEM-based photogrammetry in the three-dimensional imaging of organic-walled microfossils

Dino-Lite Micro-Photogrammetry: A Versatile Tool for Multi-Material Applications in Cultural Heritage

Portable digital microscopy (PDM) has become standard equipment in archaeological and restoration campaigns. In recent years, several studies have proposed combining PDM and micro-photogrammetry for preliminary documentation and in situ three-dimensional (3D) digitization, testing its applicability on a variety of materials and artifacts, including stone, bone, mural paintings, and small jewelry. However, limited data is available on its use with some of the most common types of artworks, such as paintings on canvas and wooden panels. In this study, the performance of micro-photogrammetry using a Dino-Lite digital microscope (Dino-Lite Europe, Almere, The Netherlands) was evaluated on five representative artistic materials: metal, stone, and paintings, including mural, canvas, and panel works. Textured mesh models were generated from the acquired datasets, and the quality of the 3D reconstruction was assessed through analysis of dense cloud confidence and Digital Elevation Model (DEM) accuracy. The metrical reliability of the micro-photogrammetric results was validated by comparing the 3D data obtained with the digital microscope against height measurements acquired using an optical microprofilometer. The results indicate that the performance of the method is strongly influenced by the physical properties of the substrates examined. Accurate and metrically consistent reconstructions were achieved for matte and textured surfaces (e.g., fresco and stone), whereas significant limitations emerged on dark or glossy painted surfaces, such as canvas and panel paintings.

Three-dimensional reconstruction and crack measurement of cultural monuments using UAV-based photogrammetry

Abstract. Three-dimensional (3D) modeling for the documentation, preservation, and management of cultural heritage is indispensable. To achieve this goal, a low-cost unmanned aerial vehicle (UAV) combined with the Structure from Motion (SfM) photogrammetric technique was utilized to build a 3D model and conduct surface crack measurements of cultural monuments. The results showed that, under simple conditions, non-specialists can easily generate accurate 3D models from UAV-acquired imagery. In this study, the statistical errors of checkpoints between 3D reconstruction and field measurements, expressed as total RMSE, ranged from 0.103 m to 0.848 m. However, the mean absolute errors of surface crack measurements between tape-based methods and 3D reconstruction ranged from 0.002 m to 0.099 m. Furthermore, UAV-SfM was applied to measure surface crack lengths on an inaccessible cultural monument. The findings demonstrated that employing the UAV-SfM photogrammetric technique for 3D reconstruction of cultural monuments is both feasible and reliable.

Preserving the Past: The 3D Documentation of Ötzi, the Iceman Mummy, and Its Archaeological Context

The three-dimensional (3D) documentation of the Similaun mummy (Ötzi the Iceman) and the associated Copper Age equipment and clothing presents unique challenges due to diverse material properties and strict conservation constraints. This study presents a comprehensive digital preservation workflow, primarily utilizing Structure from Motion (SfM) close-range photogrammetry (a method that reconstructs precise 3D geometry from overlapping 2D digital photographs), integrated with Image-Based Modeling (IBM) and Neural Radiance Field (NeRF) algorithms (a machine learning approach that models a complex scene as a continuous volumetric function method). To overcome the non-Lambertian properties of the mummy’s protective ice layer and wet skin (surfaces that reflect light specularly rather than diffusely, creating glares that can disorient standard reconstruction algorithms), a specialized Polarized Light Photography (PLP) strategy was implemented using custom-built hardware. This integration required advanced anatomical segmentation to resolve postural discrepancies caused by taphonomic processes. The resulting web-based application provides the scientific community with a metrically accurate digital twin, featuring interactive tools for cross-sectioning and X-ray visualization. By adopting a Free/Libre and Open-Source Software (FLOSS) ecosystem, this project establishes a sustainable, modular framework for future forensic investigations and diachronic monitoring, ensuring the long-term digital life of one of the world’s most significant archaeological finds.

Photogrammetry and 3D Gaussian Splatting for Cultural Heritage. Pros, Cons and Main Differences

Abstract. This paper presents a comparative analysis of traditional photogrammetric methods and 3D Gaussian Splatting (3DGS) technology in the digitisation of Cultural Heritage (CH). Two representative datasets, differing in scale and image acquisition conditions, were selected to systematically evaluate the performance of both methods in terms of visual quality, geometric accuracy, computational efficiency and stability. The results indicate that 3DGS significantly outperforms traditional photogrammetry methods in terms of rendering quality and real-time visualisation capabilities, generating more realistic and immersive visual effects. However, its geometric accuracy is generally slightly lower than that of traditional methods, a difference that is particularly pronounced in small-scale datasets or under low-resolution input conditions. Among the various implementation methods, Postshot and LichtFeld Studio demonstrated higher stability and robustness, whilst the original GraphDeco method exhibited greater sensitivity to data scale and parameter settings. Photogrammetry offers reliability in high-precision geometric reconstruction, whilst 3DGS demonstrates significant potential for complementing this with a high-fidelity visual experience. The research findings try to provide practical guidance for selecting 3D reconstruction methods across different cultural heritage application scenarios.

Three-Dimensional Identification of In Situ and Migrated Organic Matter in Shale Based on Micro-CT

Accurate differentiation of in situ organic matter (IOM) from migrated organic matter (MOM) and their three-dimensional characterization are fundamental for understanding hydrocarbon generation, migration, and accumulation in shale reservoirs. However, conventional micro-computed tomography (micro-CT) cannot distinguish organic matter subtypes due to insufficient resolution. This study establishes a novel workflow integrating micro-CT with high-resolution scanning electron microscopy (SEM) through image registration. A cubic sample with parallel opposite faces facilitated ion milling and SEM-CT registration. Under SEM supervision, IOM, MOM, and pore–fracture space were interpreted in the micro-CT volume. Applied to the Chang 7 Member shale in the Ordos Basin, results reveal IOM occupies the largest volume fraction (6.96%), followed by MOM (0.94%), while pore–fracture space accounts for only 0.13%. MOM exhibits four morphological types interconnected by throat-like bridges at the ~3.7 μm scale. MOM and pore–fracture components share similar thickness distributions peaking at ~3.7 μm, reflecting their common inheritance from the pore–throat system, whereas IOM is controlled by sedimentary and compactional processes, favoring finer fractions (<3.5 μm). MOM volume far exceeds current pore space, indicating early hydrocarbons predominantly filled connected networks. This workflow overcomes conventional micro-CT limitations, providing a more objective approach for micro-component identification in shale micro-CT data.

Integrated Photogrammetric, Petrographic, and Mechanical Assessment of Plutonic Rocks as Dimension Stone Resources