Browsing by Author "Prittinen, Markus"

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    Comparison of camera equipment for photogrammetric digitization of hard rock tunnel faces
    (2021-05-17) Prittinen, Markus; Janiszewski, Mateusz; Insinööritieteiden korkeakoulu; Leveinen, Jussi
    It is important to have good data for making safe tunnel designs. An understanding of the prevailing discontinuities is crucial to evaluate the quality of the rock mass and reinforcement needs. Photogrammetry using Structure-from-Motion is a 3D-scanning technique from which one can make 3D representations of real-life objects using 2D-photos. The 3D-models allows for more automated and faster discontinuities mapping than traditional compass methods. The research location is the Underground Research Laboratory of Aalto University (URLA), which is a tunnel complex located in underneath Otaniemi campus at Aalto University in Espoo Southern Finland. The research questions are: What are the challenges in tunnel photogrammetry? What are the most efficient methods in capturing tunnel environments? Are 360- and action cameras a viable alternative to more traditional photogrammetry methods using DSLR cameras? Do the methods used produce 3D-models good enough for identifying rock futures and for doing measurements and discontinuity mapping? In this thesis different cameras are compared for Structure-from-Motion photogrammetry, a DSLR camera, a 360-camera, and a GoPro rig that was developed during the research. The GoPro rig combines four GoPro action cameras using a plastic frame and 3D-printed parts and can be used both handheld and on a tripod. An experiment is done using constraints for how close to an unsupported walls work can be done, to simulate a tunnel under construction. The accuracy, speed and resolution of each method is measured. The geometric accuracy is compared with measurements from a laser measurement tool. Traditional compass measurements of discontinuity sets are compared with measurements from 3D-models gathered, including semi-automated measurements of discontinuities in Discontinuity Set Extractor. The results show that out of the methods compared the DSLR method is most accurate and the 360-camera least accurate, yet each method produces a point cloud accurate enough for automatic discontinuity set measurements. Out of the methods tested the GoPro rig was proven to be both the fastest and cheapest method in acquiring images for photogrammetry.
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    Rapid photogrammetric method for rock mass characterization in underground excavations
    (2023-05-24) Janiszewski, Mateusz; Prittinen, Markus; Uotinen, Lauri; Torkan, Masoud; Rinne, Mikael; Department of Civil Engineering; Sigursteinsson, Haraldur; Ingimarsson, Atli Karl; Mineral Based Materials and Mechanics
    Underground excavation mapping and rock mass characterization are critical for ensuring the safety, proper design, and maintenance of underground infrastructure. Traditional mapping methods typically involve manual inspections and measurements that require contact with the tunnel surface, which can be time-consuming, expensive, and pose safety risks to personnel. In recent years, photogrammetry has emerged as an alternative method for generating high-resolution digital 3D models of tunnels, enabling rapid and remote rock mass measurements. In this paper, we present a method for tunnel and stope scanning using photogrammetry and remote rock mass mapping from 3D models. Two case studies are presented to demonstrate the effectiveness of the proposed method. In the first case, a multi-camera rig consisting of action cameras is used for videobased photogrammetric reconstruction of underground tunnel excavation. The rock mass data is then extracted from the model and visualized. In the second case, a drone workflow is used to map out rock mass features in stopes. Images taken with the drone are processed to create a 3D point cloud of the stope, which is then used to extract discontinuities from the rock mass surfaces. The orientation and spacing of these discontinuities are measured and visualized on top of the photorealistic 3D mesh of the stope for inspection. The proposed method significantly reduces the data capture process. The advancements in camera and software technologies have made it possible to acquire rapid and accurate 3D models of underground excavations that can be used as a source of rock mass data. Our results demonstrate that photogrammetry is a robust approach for underground rock mass inspection and remote mapping.
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    Rapid tunnel scanning using a 360-degree camera and SfM photogrammetry
    (Institute of Physics Publishing, 2023-01-10) Janiszewski, Mateusz; Prittinen, Markus; Torkan, Masoud; Uotinen, Lauri; Department of Civil Engineering; Mineral Based Materials and Mechanics; Department of Civil Engineering
    Photogrammetric scanning can be employed for the digitization of underground spaces, for example for remote mapping, visualization, or training purposes. However, such a technique requires capturing many photos, which can be laborious and time-consuming. Previous research has demonstrated that the acquisition time can be reduced by capturing the data with multiple lenses or devices simultaneously. Therefore, this paper demonstrates a method for rapid scanning of hard rock tunnels using Structure-from-Motion (SfM) photogrammetry and a 360-degree camera. The test was performed in the Underground Research Laboratory of Aalto University (URLA). The tunnel is located in granitic rocks at a depth of 20 m below the Otaniemi campus in Espoo, Finland. A 10 m long and 3.5 m high tunnel section with exposed rock was selected for this study. Photos were captured using the 360-degree camera from 27 locations and 3D models were reconstructed using SfM photogrammetry. The accuracy, speed, and resolution of the 3D models were measured and compared with models scanned with a digital single-lens reflex (DSLR) camera. The results show that the data capture process with a 360-degree camera is 6x faster compared to a conventional camera. In addition, the orientation of discontinuities was measured remotely from the 3D model and the digitally obtained values matched the manual compass measurements. Even though the 360-degree camera-based 3D model's quality was visually inferior to the DSLR model, the point cloud had sufficient accuracy and resolution for semi-automatic discontinuity measurements. The quality of the models can be improved by combining 360-degree and DSLR photos which result in a point cloud with 3x higher resolution and 2x higher accuracy. The results demonstrated that 360-degree cameras can be used to rapidly digitize underground tunnels.