We performed a stereo-photogrammetric (SPG) analysis of more than 1500 Rosetta/OSIRIS NAC images of comet 67P/Churyumov-Gerasimenko (67P). The images with pixel scales in the range 0.2−3.0 m/pixel ...were acquired between August 2014 and February 2016. We finally derived a global high-resolution 3D description of 67P’s surface, the SPG SHAP7 shape model. It consists of about 44 million facets (1−1.5 m horizontal sampling) and a typical vertical accuracy at the decimeter scale. Although some images were taken after perihelion, the SPG SHAP7 shape model can be considered a pre-periheliondescription and replaces the previous SPG SHAP4S shape model. From the new shape model, some measures for 67P with very low 3σ uncertainties can be retrieved: 18.56 km3 ± 0.02 km3 for the volume and 537.8 kg/m3 ± 0.7 kg/m3 for the mean density assuming a mass value of 9.982 × 1012 kg.
Anatomic awareness of the structural connectivity of the brain is mandatory for neurosurgeons, to select the most effective approaches for brain resections. Although standard microdissection is a ...validated technique to investigate the different white matter (WM) pathways and to verify the results of tractography, the possibility of interactive exploration of the specimens and reliable acquisition of quantitative information has not been described. Photogrammetry is a well-established technique allowing an accurate metrology on highly defined three-dimensional (3D) models. The aim of this work is to propose the application of the photogrammetric technique for supporting the 3D exploration and the quantitative analysis on the cerebral WM connectivity.
The main perisylvian pathways, including the superior longitudinal fascicle and the arcuate fascicle were exposed using the Klingler technique. The photogrammetric acquisition followed each dissection step. The point clouds were registered to a reference magnetic resonance image of the specimen. All the acquisitions were coregistered into an open-source model.
We analyzed 5 steps, including the cortical surface, the short intergyral fibers, the indirect posterior and anterior superior longitudinal fascicle, and the arcuate fascicle. The coregistration between the magnetic resonance imaging mesh and the point clouds models was highly accurate. Multiple measures of distances between specific cortical landmarks and WM tracts were collected on the photogrammetric model.
Photogrammetry allows an accurate 3D reproduction of WM anatomy and the acquisition of unlimited quantitative data directly on the real specimen during the postdissection analysis. These results open many new promising neuroscientific and educational perspectives and also optimize the quality of neurosurgical treatments.
•Photogrammetry enhances the anatomic awareness of brain connectivity.•The photogrammetric method allows interactive visualization of white matter tracts.•Many measurements are possible after dissection based directly on the real specimen.•Coregistration between the MR mesh and the photogrammetric points cloud is accurate.•Photogrammetry has promising didactic, neuroscientific, neurosurgical applications.
•An Auxiliary Measuring Tool (AMT) with elaborate structure is designed, which can represent the center, normal and in-plane rotation of the flange face in different styles and sizes.•A novel method ...for calibrating the AMT is proposed.•An efficient photogrammetry-based approach to attitude inspection of the flange faces on multi-branch welded tubes is put forward using the AMT.•Experiments demonstrate the high performance of the proposed method on real welded tubes.
The attitudes (including positions and orientations) of flange faces on a multi-branch welded tube are critical to tube installation quality. However, it lacks appropriate approach for flange attitudes inspection. Given the inspection requirements, a novel Auxiliary Measuring Tool (AMT) is designed. A photogrammetry-based approach is put forward to inspect the attitude errors of the flange faces with the aid of the AMT. The specifically designed AMT can achieve flange face centering through a three-jaw chuck structure and establish in-plane rotation by employing a slider to locate the reference bolt hole. An ingenious calibration method is proposed to establish the AMT coordinate frame (ACF) and obtain the marker points’ coordinates in ACF. With the calibrated AMTs attached to each flange, the flange attitude error can be efficiently evaluated by simply capturing a set of images of the tube. Experiments on two welded tubes demonstrate the high performance of the proposed method.
In the on-orbit application of photogrammetry, constraints on thermal control resources or aging of thermal control equipment will trigger increased fluctuations in the camera operating environment ...temperature. Consequently, the parameters of the camera imaging model vary, such that the measurement accuracy is reduced. Accordingly, the accurate prediction of the camera imaging parameters (e.g., Camera Interior Parameters (CIP) and Lens Distortion Parameters (LDP)) at variable temperatures takes on critical significance.
First, a novel method, termed as Virtual Multi-station Camera Calibration (VMCC), is proposed to calibrate the CIP and LDP with each frame at variable temperatures. Second, the Variational Mode Decomposition method combined with the Northern Goshawk Optimizer (NGO-VMD) is employed to decompose the camera imaging parameter signals obtained from VMCC, yielding the n Intrinsic Mode Functions (IMFs) contained in the respective parameter signal. Third, the Generalized Regression Neural Network combined with the Dung Beetle Optimizer (DBO-GRNN) is employed, such that the smoothness parameter q of the GRNN is iteratively optimized based on the camera imaging parameter prediction error. Lastly, the CIP and the LDP are accurately predicted at different temperatures in accordance with the temperature data from multiple parts of the camera.
Based on this study, a reliable dataset of camera imaging parameter responses at variable temperatures can be generated for the on-orbit photogrammetry system. Furthermore, the prediction accuracy and immense application potential of neural network modeling methods are demonstrated in camera parameter prediction.
•A high-precision single-frame calibration method was first developed for photogrammetry camera imaging parameters.•Strictly carried out the experiment in a long-term, multi-period, and large-scale variable temperature environment.•The DBO-GRNN was employed to perform optimal prediction on the camera imaging parameter for the first time.•The prediction performance of the DBO-GRNN was enhanced by further enriching the data features using the NGO-VMD.
An automated, fixed-location, continuous time-lapse camera system was developed to analyze the existence of rockfall precursory movements and quantify volume changes after detachments. It was ...implemented to monitor the basaltic formation on which Castellfollit de la Roca village is built. Due to the geometrical conditions of the area, the camera system consists of three digital cameras managed by a control unit that contains a Raspberry Pi 4 microprocessor. Images taken every day are sent to a server for processing. A workflow has been developed to work with a set of images with an irregular time interval to detect precursor movement. The first step consists of matching the images with a reference master image and filtering the vegetation to improve the process using a mask obtained by a green leaf index (GLI) index. Then, the adjusted images are used for a forward-backward correlation process carried out to detect movements. If movement is detected, a 3D model is built using structure from motion (SfM) to quantify the movements. The system has been working since September 2021. During this period, movements from 0.01 to 0.5 m and several rockfalls of a small volume have been detected.
Airborne and terrestrial laser scanning and close-range photogrammetry are frequently used for very high-resolution mapping of land surface. These techniques require a good strategy of mapping to ...provide full visibility of all areas otherwise the resulting data will contain areas with no data (data shadows). Especially, deglaciated rugged alpine terrain with abundant large boulders, vertical rock faces and polished roche-moutones surfaces complicated by poor accessibility for terrestrial mapping are still a challenge. In this paper, we present a novel methodological approach based on a combined use of terrestrial laser scanning (TLS) and close-range photogrammetry from an unmanned aerial vehicle (UAV) for generating a high-resolution point cloud and digital elevation model (DEM) of a complex alpine terrain. The approach is demonstrated using a small study area in the upper part of a deglaciated valley in the Tatry Mountains, Slovakia. The more accurate TLS point cloud was supplemented by the UAV point cloud in areas with insufficient TLS data coverage. The accuracy of the iterative closest point adjustment of the UAV and TLS point clouds was in the order of several centimeters but standard deviation of the mutual orientation of TLS scans was in the order of millimeters. The generated high-resolution DEM was compared to SRTM DEM, TanDEM-X and national DMR3 DEM products confirming an excellent applicability in a wide range of geomorphologic applications.
This paper presents the background theory and the experimental implementation of a new approach for the reconstruction of the sound radiation field produced by the flexural vibration of a distributed ...structure using video image acquisitions. The study is focused on tonal flexural vibration and sound radiation at the first five resonance frequencies of a baffled flat rectangular plate model-structure. The plate is divided into a regular mesh of rectangular elements whose centres are marked with small bullets. The transverse vibrations at the grid of target points are estimated via triangulation from the images acquired with six cameras unevenly spread along half of a circle located, with a small offset, parallel to the surface of the plate. The sound radiation field in free space is then reconstructed from the Rayleigh integral, which is approximated into a finite sum over the mesh of elements. Both the flexural vibration field and the sound radiation field derived from the cameras video acquisitions are contrasted with measurements taken respectively with a laser vibrometer and an array of microphones.
•Sound radiation estimate from flexural vibration measurements using video image acquisitions.•Triangulation with multiple (i.e. more than 2) views using Bundle Adjustment.•Reconstruction of flexural deflection shapes at the first five resonances.•Reconstruction of the sound radiation fields at the first five resonances.•Validation against measurements taken with laser vibrometer and microphones array.
Abstract
Forest inventorying is time-consuming and expensive. Recent research involving photogrammetry promises to reduce the cost of inventorying. Existing photogrammetry methods require substantial ...data-processing time, however. Our aim was to reduce data-acquisition and processing times while obtaining relatively accurate diameter estimates compared to manual and other digital measurements. We developed an algorithm to identify the ground and measure diameter at breast height (dbh) or any height along a stem from the recorded video footage of trees taken with a stereo camera. Footage acquisition time, dbh root mean square error, and mean absolute error were used as comparison metrics with other methods. The time to perform three recordings for 40 trees was about 30 minutes. We recorded data at 1 m, 3 m, and 5 m from the trunk, and our dbh root mean square errors were 1.28 cm (0.50 in.), 1.47 cm (0.58 in.), and 2.57 cm (1.01 in.), respectively, using manual measures as the control. This terrestrial stereoscopic photogrammetric method is much more efficient computationally than popular terrestrial structure-from-motion photogrammetry and substantially lowers time, costs, and complexity for data acquisition and processing compared with terrestrial laser scanning.
•The pivotal role of UAVs in natural hazard management is emphasized.•The challenges in processing large UAV image datasets are addressed.•Processing time reduced via an open-source workflow on ...ReCaS-Bari HPC cluster.•Workflow performance shows up to 86% improvement over current cluster-based approaches.
Over the past two decades, natural hazards have claimed the lives of tens of thousands of people worldwide, every year. Unmanned Aerial Vehicles (UAVs) are pivotal in natural hazard management, offering rapid deployment, flexibility, and cost-effectiveness. Advances such as Beyond Visual Line Of Sight (BVLOS) missions, swarm surveying, Artificial Intelligence (AI), edge-computing, and Structure from Motion (SfM) photogrammetry enhance their high-resolution spatiotemporal data capabilities, but the need for large datasets poses challenges in terms of storage, computational resources and, especially, processing time. This work introduces an original high-performance UAV photogrammetry workflow through the implementation of an open-source distributed approach using the ReCaS-Bari HPC cluster. Performance tests of the workflow, that includes computing parallelism, GPU usage, and hybrid bundle adjustment, demonstrate a significant reduction in processing time for large UAV image datasets. The workflow outperformed current methods, reducing processing time from 908 down to 104 min for 2,691 images and handling 11,549 images in just 7.8 h (a 70 % improvement over leading commercial software). Comparative analysis with cluster-based state-of-the-art approaches revealed noteworthy reductions, reaching up to 86 % for about 7,000 images. A case study, focusing on the Basento river (Southern Italy) flood event occurred in May 2023, proved the workflow practical implications in emergency management. A change detection assessment facilitated the identification and quantification of flood-induced morphological alterations along a 3 km of river reach length within about 3 h. The results highlight the workflow utility in providing accurate and near real-time information for emergency management, enhancing situational awareness and facilitating informed decision-making during disastrous events.
The application of structure-from-motion (SfM) to generate digital terrain models (DTMs) derived from different image sources has strongly increased, the major reason for this being that processing ...is substantially easier with SfM than with conventional photogrammetry. To test the functionality in a demanding environment, we applied SfM and conventional photogrammetry to archival aerial images from Zmuttgletscher, a mountain glacier in Switzerland, for nine dates between 1946 and 2005 using the most popular software packages, and compared the results regarding bundle adjustment and final DTM quality. The results suggest that by using SfM it is possible to produce DTMs of similar quality as with conventional photogrammetry. Higher point cloud density and less noise allow a higher ground resolution of the final DTM, and the time effort from the user is 3–6 times smaller, while the controls of the commercial software packages Agisoft PhotoScan (Version 1.2; Agisoft, St. Petersburg, Russia) and Pix4Dmapper (Version 3.0; Pix4D, Lausanne, Switzerland) are limited in comparison to ERDAS photogrammetry. SfM performs less reliably when few images with little overlap are processed. Even though SfM facilitates the largely automated production of high quality DTMs, the user is not exempt from a thorough quality check, at best with reference data where available. The resulting DTM time series revealed an average change in surface elevation at the glacier tongue of −67.0 ± 5.3 m. The spatial pattern of changes over time reflects the influence of flow dynamics and the melt of clean ice and that under debris cover. With continued technological advances, we expect to see an increasing use of SfM in glaciology for a variety of purposes, also in processing archival aerial imagery.
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