José Luis Pérez-García

Precise modeling of narrow gorges is challenging due to extreme confinement, hindering visibility and accessibility. These environments often render Global Navigation Satellite Systems (GNSS)-based positioning unfeasible, a difficulty compounded by water and dense vegetation. Consequently, multi-technique data fusion is required. This study proposes a robust methodology to generate high-resolution 3D models of such complex environments by integrating multiple aerial (e.g., Unmanned Aerial Vehicles, UAVs) and terrestrial techniques. A multi-sensor approach combined UAV-Light Detection and Ranging (LiDAR) and UAV-photogrammetry for external areas with Terrestrial laser scanning (TLS), Mobile Mapping System (MMS), and Spherical Photogrammetry (SP) for the canyon floor. Furthermore, the representativeness of these 3D models was analyzed against standard Digital Terrain Models (DTMs) for determining water height levels during flood events. A one-dimensional hydraulic (1DH) model compared the 3D mesh approach with the traditional 2.5D perspective in a challenging, narrow canyon prone to flooding. Our results show that traditional 2.5D DTMs significantly over- or underestimate water levels in narrow sections—failing to account for overhangs and vertical wall irregularities—whereas high-resolution 3D meshes provide a more realistic representation of hydraulic behavior. This work demonstrates that multi-sensor data fusion is essential for accurate flood risk management and infrastructure planning in complex fluvial environments.

The use of digital photogrammetry and laser data acquisition systems, along with the ability to mount these sensors on unmanned aerial vehicles (UAVs), has revolutionized rockfall assessment. While these techniques have facilitated numerous studies across diverse scenarios, complex environments like narrow gorges necessitate the integration of various geomatic techniques to achieve complete and accurate spatial products. To address the critical gap in the literature regarding standardized multi-sensor integration in narrow gorges, this study presents a novel methodology for the cohesive integration of data from these techniques, leveraging their respective strengths to generate reliable products for rockfalls risk assessment. To validate the methodology, we applied this approach to a challenging rockfall susceptibility study at the Caminito del Rey in Málaga, Spain. The site presented significant complexities, including vertical walls hundreds of meters high with abundant overhangs, and canyons as narrow as 10 m, severely limiting single-technique approaches. The successful integration of these diverse datasets yielded a comprehensive, very high-resolution point cloud (1–10 cm density), among other products, covering the entire study area, making it ideal for detailed rockfall assessment and simulation. The approach has demonstrated that data fusion from multiple techniques supposes an advantage because one supports the other both in data coverage and in processing. Although processing the extensive acquired information presented a significant challenge, a successful balance between data volume and processing capacity was achieved, ensuring the outputs met the specific requirements for these studies.

Kinematic analyses are essential for identifying potential detachment mechanisms in rock masses, influenced by fracturing, direction, and slope. Traditionally, these analyses utilize digital stereographic templates to assess whether fracture orientations and dips predispose the mass to planar sliding, wedge failure, or toppling. However, natural rock formations often exhibit complex geometries with varying orientations and overhangs, complicating standard assumptions of directional uniformity. This study addresses such complexities by integrating a Digital Elevation Model (DEM) with Geographic Information Systems (GIS) to calculate the orientation and slope of rock walls and perform geometric calculations. We employ the SAGA GIS tool WEDGEFAIL, which automates these calculations. Enhancements to this tool facilitate semi-automatic assessments of failure mechanisms using topographical and structural data in both 2D and 3D formats. A custom Python script is also developing on high-resolution topographic data from a rock wall at Caminito del Rey (Málaga), represented as a raster (2.5D) and point cloud (3D). This data was augmented by structural evaluations from in-situ geomechanical stations and virtual measurements on the point cloud, employing automatic discontinuity recognition techniques. The results led to a susceptibility map for detachment in plan and elevation views of the analyzed wall. In-situ visual inspections, drone videos, and photorealistic 3D models in virtual environments confirmed a significant spatial correlation between identified susceptible areas and zones prone to detachment, as indicated by the semi-automatic method. This approach in development will enhance the precision of kinematic analyses in complex rock formations and provides a robust framework for assessing rock stability hazards.

This study describes the methodology and main results obtained after applying several geomatic techniques, based on the fusion of data acquired by several sensors, to document the recovery works carried out in an abandoned church. A century ago, the façade was moved to a museum to ensure its preservation. In addition to documentary purposes, a secondary goal is the virtual repositioning of a model of this element on that of the church. The method takes advantage of the potential of each technique, considering the acquisition of geometry based mainly on laser scanning techniques and radiometry on photogrammetry. The results include 3D models and orthoimages, which are used to perform a stratigraphic study. The 3D model of the façade has been repositioned in the general one, considering common geometries previously fitted in both models and repeating part of the photogrammetric process, using masks to define the image areas related to the church and the façade. Therefore, we obtained a 3D model with the façade included in it. This procedure has demonstrated its feasibility despite the existence of different environmental conditions in both areas. Using these results, we have also developed a BIM to allow for the management of future restoration works.

This study shows the results of the analysis of the photogrammetric use of 360-degree cameras in complex heritage-related scenes. The goal is to take advantage of the large field of view provided by these sensors and reduce the number of images used to cover the entire scene compared to those needed using conventional cameras. We also try to minimize problems derived from camera geometry and lens characteristics. In this regard, we used a multi-sensor camera composed of six fisheye lenses, applying photogrammetric procedures to several funerary structures. The methodology includes the analysis of several types of spherical images obtained using different stitching techniques and the comparison of the results of image orientation processes considering these images and the original fisheye images. Subsequently, we analyze the possible use of the fisheye images to model complex scenes by reducing the use of ground control points, thus minimizing the need to apply surveying techniques to determine their coordinates. In this regard, we applied distance constraints based on a previous extrinsic calibration of the camera, obtaining results similar to those obtained using a traditional schema based on points. The results have allowed us to determine the advantages and disadvantages of each type of image and configuration, providing several recommendations regarding their use in complex scenes.

The medieval wall of Jaén is a historical monument that has suffered from the apathy of institutions in recent years, causing its calamitous current status. This study focuses on the previous geomatic tasks developed to obtain a 3D documentation of this site in order to manage future restoration works. The methodology included the integration of data obtained using several geomatic techniques, such as LiDAR and photogrammetry at three scale levels, from the general to the particular. Therefore, data fusion is the main aspect of this methodology, developed in an attempt to take advantage of the benefits of each technique. The application demonstrated the feasibility of using the methodology in order to obtain a complete documentation, including 3D models, orthoimages and DEMs, at several scales with different resolutions and point densities. In addition, we also considered the accuracy of data and products with respect to the project requirements. Another aspect to highlight is the reduction in acquisition time by minimizing the necessity of conducting classic surveying to obtain georeference data. The results show reliable products for supporting restoration tasks and allowing the development of a BIM application to manage them, but also for the dissemination of knowledge regarding this unknown monument.

This study describes a methodology for obtaining a geometric documentation of a medium-sized archaeological area by applying various geomatic techniques. The procedure considers the obtainment of products at several scales, from the entire site to small artifacts, and at several dates, in order to model the evolution of the archaeological work. The methodology includes both LiDAR and photogrammetry, using the LiDAR point clouds to support the geometry obtained using photogrammetry and adding texture from this source. The technique used was adapted to the circumstances of the scene by considering the scale level (resolution and accuracy), complexity, and other requirements of the project. In the case of LiDAR, terrestrial laser scanning and structured-light scanning were used, and the aerial photogrammetry used two types of RPAS (medium and low flight height), close range photogrammetry with a conventional camera, and very close-range photogrammetry with a conventional camera mounted with a macro lens. The methodology demonstrated its feasibility for performing these types of studies, providing products adapted to the required scale level. All results were integrated into a website, including a map that allows user interaction and displays products at a selected zoom level, according to their scale level. The website also displays 3D models of the scenes and objects studied.

Highlights: A new methodology is presented to develop geometrical analysis of burial structures based on 3D models. The methodology has been applied to three contiguous burial structures (hypogea), allowing the researchers to analyse some constructive aspects such as dimensions, proportions, orientations, flatness and inclinations. Results have demonstrated the advanced skills achieved by ancient Egyptians in construction techniques. This study describes the methodology developed and the main results obtained when analysing the geometrical behavior of three adjacent burial structures located in southern Egypt. The rock-cut tombs are composed of complex geometries such as halls, corridors, chambers and vertical shafts. Among other determining aspects, this complexity greatly conditioned the data acquisition and processing work. In this context, the main objective of this study was to develop a new methodology for obtaining geomatic products that support a complete geometrical analysis of the tombs. The researchers have used photogrammetric and laser scanning surveys to obtain accurate 3D models on a common reference system. The procedure used included obtaining several secondary products, such as several geometries (planes and cylinders) fitted from point clouds or plans and sections obtained from the 3D models. The geometric analysis has included several aspects: dimensions, proportions, orientations, wall flatness, inclinations, etc., and it is based on these products. The results obtained suggest and confirm several hypotheses about the constructive aspects of these hypogea based on a large amount of data, including the determination of a proportional canon used by the ancient Egyptians to plan and perform the excavation works of each funerary structure. The application of this methodology has demonstrated that this type of analysis is viable to unveil some important aspects of these structures and the constructive procedures carried out almost four millennia ago.

The archaeological site of Qubbet el Hawa contains one of the largest necropolis in southern Egypt. At this burial site the governors and high officials of the southernmost province of Egypt were buried from the Late Old Kingdom to the Late 12th Dynasty. This study aims to analyze one of the largest funerary complexes (QH34h), belonging to the local governor Khunes, and other annexed tombs of his relatives. This large funerary complex, with a great funerary chapel, includes an ascending stairway and a monumental courtyard. It was built during the last part of the reign of Pepy II (2216-2153 BC). It underwent a set of architectural transformations throughout its history, including several collapses and, centuries later, it was chosen by a Coptic community to establish a Christian church and other monastic places. The main aim of the present paper is to analyze how the sacred space changed over time and the architectonic spaces were used with different purposes.

This paper deals with the use of aerial photogrammetry and LiDAR techniques to analyze landslide activity over a long time span—just over 32 years. The data correspond to several aerial surveys (1984, 1996, 2001, 2005, 2009, 2010, 2011, 2013 and 2016) covering an area of about 50 km² along highway A-44, near Jaén (Southern Spain). An ad hoc combined photogrammetric and LiDAR aerial survey of 2010 was established as the reference flight. This flight was processed by means of direct orientation methods and iterative adjustments between both data sets. Meanwhile, historical flights available in public geographical data servers were oriented by transferring ground control points from the reference flight. Then, digital surface models (DSMs) and orthophotographs were generated, as well as the corresponding differential models (DoDs), which, after the application of filters and taking into account the estimated uncertainty of ± 1 m, allowed us to identify true changes on the ground surface. This analysis, complemented by photointerpretation, led us to obtain a landslide multitemporal inventory in the study area that was analyzed in order to characterize the landslide type, morphology and activity. Three basic typologies were identified: rock falls–collapses, slides and flows. These types present different morphometric properties (area, perimeter and height interval) and are associated with different conditions (height, slope, orientation and lithology). Moreover, a set of monitoring areas, common for the different flights, was also used to analyze the activity throughout the study period. Thus, some more active periods were identified (2009–2010, 2010–2011, 2011–2013 and 1996–2001) among other less active ones (1984–1996, 2001–2005, 2005–2009 and 2013–2016), which are related to rainy events and dry years, respectively.