GNSS–Camera Systems for Heritage Documentation. Accuracy assessment of measurements of inaccessible points and preliminary tests in photogrammetric applications
Jul 2026· The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences· 0 citations· 2 references
Abstract
Abstract. The measurement of Ground Control Points is a crucial but time-consuming step in photogrammetric surveys, especially in the Built Heritage domain. This study investigates the use of a new generation Global Navigation Satellite System receiver equipped with an integrated camera to measure inaccessible points (to be used as GCPs, e.g. on building façades), combining satellite positioning and photogrammetry in a single device. The approach was tested on a historical building using both the tested GNSS-camera system and traditional Total Station topographic measurements as reference. Results show that the proposed method can achieve centimetric accuracy, with horizontal and vertical errors of about 3-5 cm (in line with the adopted NRTK service). While a small systematic shift was observed, the overall geometric consistency of the measured points remained within acceptable limits for many heritage documentation applications. Additionally, the georeferenced images acquired by the system were successfully used in a Structure from Motion (SfM) direct georeferencing workflow, producing 3D models and orthophotos with good metric reliability when compared to other data, such as TLS scans. The study demonstrates that GNSS-camera systems can significantly reduce fieldwork time while providing reliable spatial data, representing a promising solution to be integrated into heritage documentation pipelines in an efficient and flexible way.
Abstract. The 3D documentation of complex scenes—characterized by restricted spaces, irregular geometries, and poor lighting—remains a significant challenge in cultural heritage. This study proposes a rapid data acquisition methodology based on the multi-sensor fusion of Terrestrial Laser Scanning (TLS) and Spherical Photogrammetry (SP). The approach was validated in two distinct complex environments: an ancient Egyptian rock-cut tomb (QH36, Aswan, Egypt) and a natural Iberian sanctuary cave (Cueva de la Lobera, Jaén, Spain). The methodology uses TLS to establish a high-precision geometric backbone, achieving registration errors below 0.5 cm. By extracting Ground Control Points (GCPs) directly from the TLS point cloud, the reliance on traditional total station surveying was significantly reduced, enhancing fieldwork efficiency. SP was implemented to obtain realistic textures and to support geometry by using a 360-degree multi-camera with integrated LED lighting, providing full spherical coverage and high-resolution textures. Results indicate that SP is at least six times faster than conventional photogrammetry. Furthermore, the use of TLS-derived meshes enabled advanced digital masking to remove non-interest objects (e.g., archaeological equipment) from the final models. While conventional photogrammetry remains the benchmark for fine architectural details, this research demonstrates that the TLS-SP fusion is the most viable solution for the rapid, high-accuracy documentation of constrained heritage sites. This hybrid workflow ensures geometric integrity while drastically reducing acquisition times, providing a robust framework for future archaeological and conservation projects.
A. Mozas-Calvache, José Luis Pérez-García, J. M. Gómez-López et al.· The International Archives o...· 0 citations
This study evaluates the metric reliability of nadir and hybrid RTK-UAV photogrammetric models for surface detail extraction on a two-story building without using Ground Control Points (GCPs). Two photogrammetric models were generated: a standard model based only on nadir images and a hybrid model combining nadir, oblique, and manual façade-oriented images. Both models were assessed using terrestrial reference data obtained from GNSS and reflector less total station measurements. The evaluation was performed at three levels: point-based, length-based, and surface-based comparisons. The point-based results indicate that the nadir model allowed 21 of the 35 reference points to be reconstructed, whereas the hybrid model allowed the 3D positions of all. The hybrid model also substantially improved vertical and overall 3D accuracy, reducing the ΔZ MAE from 0.355 m to 0.029 m and the 3D RMSE from 0.454 m to 0.046 m. In the length-based analysis, the nadir model was included where both endpoints of a selected linear element could be clearly identified. The nadir model allowed only 4 of the 14 selected length pairs to be measured, whereas the hybrid model allowed all 14 length pairs to be evaluated. On the other hand, the hybrid model had close agreement with the reference lengths, with a MAE of 0.012 m and RMSE of 0.016 m. Also, there is no statistically significant difference observed between reference and model lengths. In the surface-based comparison, the nadir model could represent only 4 of 7 reference surfaces, a limited number of reference surfaces, whereas the hybrid model enabled all selected surfaces to be evaluated, including upper-floor and under-eave regions. Although the nadir model produced lower average errors on some reconstructed surfaces, its limited surface coverage reduced its practical applicability. Overall, the findings demonstrate that hybrid RTK-UAV image acquisition provides a more robust and reliable solution than nadir-only acquisition for building surface documentation, particularly in façade areas with restricted visibility.
M. N. Alkan· International Journal of Geo...· 0 citations
This study presents a UAV photogrammetry and GIS-based workflow for generating high-accuracy three-dimensional cadastral models in urban environments. The proposed framework integrates RTK-enabled UAV image acquisition, ground control point (GCP) surveying, photogrammetric reconstruction, GIS-based spatial data management, and accuracy assessment within a unified workflow. A total of 454 aerial images were acquired and processed to generate a dense point cloud, digital surface model, orthomosaic, and textured 3D urban model. Positional accuracy was evaluated using 15 independently surveyed RTK GNSS checkpoints distributed throughout the study area. The results demonstrated a relative accuracy of 1.7 cm and an absolute positional accuracy of 2.47 cm based on independent checkpoint validation, confirming the suitability of the proposed workflow for large-scale cadastral mapping applications. The generated 3D cadastral model enabled accurate extraction and visualization of parcel boundaries, building footprints, and urban spatial features. The findings indicate that UAV photogrammetry combined with GIS provides a cost-effective and reliable approach for developing high-precision three-dimensional cadastral datasets that support modern land administration, urban planning, and digital city management.
Salar Mirzapour, Z. Azizi, H. Zavar et al.· Scientific Reports· 0 citations
Abstract. Mobile mapping systems usually include cameras designed for 360° imaging and laser scanning point cloud coloring. However, the multi-camera systems are rarely optimized for producing photogrammetric image-based point clouds in road environments. In this study, we built a mobile 5-camera system and assessed its performance in determining the 3D geometry of road surfaces. The evaluation was carried out in two parts: First, we examined how driving speed ranging from 3 to 20 km/h affect the quality of the point cloud produced by the mobile multi-camera system. We compared this data to reference measurements of road surface samples obtained using a laboratory-grade structured-light scanner. Second, we compared the point cloud produced by the mobile multicamera system to that generated by a terrestrial laser scanner from a 10-meter single lane road section. In the case of the driving speed tests, the point cloud comparisons resulted an average 3D distance from 0.09 mm to 0.31 mm, and a standard deviation from 0.29 mm to 0.50 mm. On the road section, the average 3D distance between the points clouds was 0.97 mm, with a standard deviation of 0.59 mm. These results demonstrate the capability of the mobile multi-camera system in 3D reconstruction of road surfaces and encourage further research into the feasibility of multi-camera system configurations for studying road surface quality parameters and identifying the dimensions of road damages.
M. Vaaja, M. Sarlin, Eino Waldén et al.· The International Archives o...· 0 citations
Abstract. The Valpelline Valley, located in the northern Aosta Valley (Italy) along the Swiss border, is a typical Alpine valley shaped by glacial and fluvial processes. Characterized by a large altitudinal range (900-4000 m a.s.l.) and hosting glaciers feeding the Place Moulin reservoir, the area plays a key role in regional hydroelectric production. Since 2020, GlacierLAB has been conducting glacier monitoring activities through biannual aerial photogrammetric surveys, overcoming the logistical constraints imposed by the steep and inaccessible morphology of the valley.The surveys were performed using a medium-format camera mounted under an aircraft wing and equipped with GNSS and IMU systems. Due to the lack of synchronization between the camera shutter and GNSS receiver, georeferencing relied on Ground Control Points (GCPs), whose spatial distribution is often limited in high-mountain environments. This condition makes camera calibration a critical factor for ensuring reliable multi-temporal analysis.This study investigates the behavior of the radial distortion parameter k1 using images previously corrected for optical distortion. A multi-run bundle adjustment strategy was applied in Agisoft Metashape, including baseline configurations, global and image-wise estimation of k1, and robustness tests under different GCP setups. Statistical analyses reveal a systematic and significant dependence of k1 on the vertical camera–terrain distance.However, comparison with a theoretical atmospheric model based on the Saastamoinen formulation shows weak correlation, indicating that the observed effect cannot be attributed solely to atmospheric refraction. Instead, k1 acts as a compensatory parameter absorbing depth-dependent systematic effects related to block geometry and acquisition conditions.
M. Macelloni, N. Grasso, A. Cina· The International Archives o...· 0 citations
Abstract In the 21st century, the cost of personal computers and digital cameras has reduced significantly. This technological advancement means that collecting large amounts of data has become inexpensive. The reduced cost of data collection corresponds with a decline in the awareness of meticulous planning in photogrammetric projects and an increase in the volume of unstructured data. CyArk, a non-profit organization based in California, has documented heritage sites globally using a combination of LiDAR and photogrammetry and published their datasets through the OpenHeritage3D portal, an open-access platform. These datasets often lack proper documentation, standardization, and modularization. Although these data can create photorealistic models, they do not contain survey data and meticulous project planning, resulting in unstructured data. While existing literature explores the reusability of CyArk data through 3D modelling, mapping, and architectural drawing, the current literature lacks a systematic review of CyArk’s capture process, OpenHeritage3D’s archival method, and the accuracy of the 3D data. This study reviews the datasets from OpenHeriage3D using RealityCapture and 3Dsurvey software. The two case studies aim to deliver traditional 2D façade documentation from LiDAR and photogrammetric data. Ultimately, this article provides suggestions for CyArk and OpenHeritage3D to improve the process of data creation and storage.
Chung-Ting Esmond Lo, G. Bevan· Preservation, Digital Techno...· 0 citations
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