Dense Clouds Research Articles

Detectability of the passage of the heliosphere through an interstellar cloud with cosmogenic nuclides in lunar soil

As the Sun traverses interstellar space it may encounter interstellar molecular clouds (IMCs) characterised by higher particle densities than in the ambient interstellar medium. These occurrences have, for example, been proposed to explain the increase of ^60Fe measured in sea sediments. Magnetohydrodynamic (MHD) simulations show that such IMC crossings effectively shrink the heliosphere, thereby reducing its ability to modulate the incident spectrum of galactic cosmic rays (GCRs). Therefore, the hallmark of such encounters in the past may be increased GCR intensities, which can be detected via analyses of cosmogenic nuclides in lunar regolith samples. The present study proposes a method for testing whether such IMC crossings have indeed occurred in the past, by analysing the rates at which the long-lived cosmogenic nuclide (lifetime 1.0 Myr) is formed in lunar soil samples. Cosmogenic nuclide production rates at varying depths in lunar soil are related to a corresponding GCR modulation potential, which in turn is related to a corresponding modulation boundary, and hence interstellar density, via a scaling relation based on published MHD simulation results. A lower limit for the detectability of past heliospheric crossings of IMCs is presented, governed by the amount of time spent in such a cloud: shorter passages may be undetectable, but longer passages would be clearly observable. However, we find no evidence of the Solar System encountering a cold, dense cloud. Lunar cosmogenic nuclides represent a powerful tool whereby the past modulation history of the heliosphere can be revealed over timescales of millions of years, which in turn can provide invaluable insights as to the past interstellar environment encountered by the Sun. However, techniques such as the one proposed here will benefit greatly from new, higher-precision analyses of existing lunar samples.

Dense point cloud map construction based on ORB-SLAM2 and cross-attention network

Dense point cloud map construction based on ORB-SLAM2 and cross-attention network

Assessment of the Efficiency of Lidar Data Reduction Methods in the Generation of Digital Elevation Models

Digital Elevation Models (DEMs) have become an indispensable tool for a wide range of surface investigations, facilitating critical engineering and scientific assessments. While there are several methods for acquiring input data, LiDAR technology offers a significant advantage by providing a highly efficient and cost-effective means of data acquisition. The technology produces dense point clouds, enabling the construction of high resolution and high quality DEMs. However, the inherent density and large volume of these point clouds present significant data processing challenges, potentially introducing errors into the final DEM. While numerous data reduction methods for LiDAR point clouds have been proposed, previous studies have yielded inconclusive results regarding the optimal method for generating DEMs from LiDAR data, highlighting the need for further research to establish best practices in the field of earth surface analysis. The main objective of the present study is to assess the most relevant LiDAR data reduction methods and new proposals in order to determine which of them are more technically feasible. To this end, a bibliographical study was carried out on the nine selected methods, which allowed their comparison by means of a criteria-based matrix. According to the results obtained, it was determined that the methods with the best performance in LiDAR data reduction are the PpC method, the OptD method, the Uniform 3D Grids and the RpA algorithm.

Cosmic-ray acceleration and escape from supernova remnant W44 as probed by Fermi-LAT and MAGIC

Context. The supernova remnant (SNR) W44 and its surroundings are a prime target for studying the acceleration of cosmic rays (CRs). Several previous studies established an extended gamma-ray emission that is set apart from the radio shell of W44. This emission is thought to originate from escaped high-energy CRs that interact with a surrounding dense molecular cloud complex. Aims. We present a detailed analysis of Fermi-LAT data with an emphasis on the spatial and spectral properties of W44 and its surroundings. We also report the results of the observations performed with the MAGIC telescopes of the northwestern region of W44. Finally, we present an interpretation model to explain the gamma-ray emission of the SNR and its surroundings. Methods. We first performed a detailed spatial analysis of 12 years of Fermi-LAT data at energies above 1 GeV, in order to exploit the better angular resolution, while we set a threshold of 100 MeV for the spectral analysis. We performed a likelihood analysis of 174 hours of MAGIC data above 130 GeV using the spatial information obtained with Fermi-LAT. Results. The combined spectra of Fermi-LAT and MAGIC, extending from 100 MeV to several TeV, were used to derive constraints on the escape of CRs. Using a time-dependent model to describe the particle acceleration and escape from the SNR, we show that the maximum energy of the accelerated particles has to be ≃40 GeV. However, our gamma-ray data suggest that a small number of lower-energy particles also needs to escape. We propose a novel model, the broken-shock scenario, to account for this effect and explain the gamma-ray emission.

Influence of target area density parameter and electrostatic pulse width modulation variable nozzle on physical characteristics of precision spray

This paper discusses the observation of different precision spraying processes of pulse width modulated variable sprinkler in electrostatic field under different target area densities and discusses the physical characteristics of precision spraying under electrostatic action of different target area density parameters and pulse width modulated variable sprinkler, the influence of various parameters of precision spraying on spray settling rate. Using different environmental protection liquid, the point cloud density detected by the laser Light Detection and Ranging (LiDAR) sensor was used to test different targets and obtain the physical parameter of area density. The area density of the target was differentiated and classified. According to the area density of the target of different categories, multidirectional research was carried out with the conductivity of the liquid itself and the charge rate of the liquid itself under the action of the electrostatic pulse width modulation variable nozzle. The relationship between the three was studied, and a good spray control strategy was obtained. When the area density was 0.668, the conductivity was 10.0 mS/cm, and the spray pressure was 0.45MPa, the charge-mass ratio was the largest and the deposition effect was the best, this paper studies the improvement of the environment and the sustainable development of pesticide use in the future.

Insights Into the Role of π‐Electrons of Aromatic Aldehydes in Passivating Perovskite Defects

AbstractCarbonyl‐containing aromatic ketones or aldehydes have been demonstrated to be effective defect passivators for perovskite films to improve performances of perovskite solar cells (PSCs). It has been claimed that both π‐electrons within aromatic units and carbonyl groups can, separately, interact with ionic defects, which, however, causes troubles in understanding the passivation mechanism of those aromatic ketone/aldehyde molecules. Herein, we clarify the effect of both moieties in one molecule on the defect passivation by investigating three aromatic aldehydes with varied conjugation planes, namely, biphenyl‐4‐carbaldehyde (BPCA), naphthalene‐2‐carbaldehyde (NACA) and pyrene‐1‐carbaldehyde (PyCA). Our findings reveal that the π‐electrons located in the conjugated system do not directly present strong passivation for defects, but enhance the electron cloud density of the carbonyl group augmenting its interaction with defect sites; thereby, with the extended conjugation plane of the three molecules, their defect passivation ability is gradually improved. PSCs incorporating PyCA with the most extended π‐electrons delocalization achieve maximum power conversion efficiencies of 25.67 % (0.09 cm2) and 21.76 % (14.0 cm2). Moreover, these devices exhibit outstanding long‐term stability, retaining 95 % of their initial efficiency after operation for 1000 hours at the maximum power point.

UnDER: Unsupervised Dense Point Cloud Extraction Routine for UAV Imagery Using Deep Learning

Extraction of dense 3D geographic information from ultra-high-resolution unmanned aerial vehicle (UAV) imagery unlocks a great number of mapping and monitoring applications. This is facilitated by a step called dense image matching, which tries to find pixels corresponding to the same object within overlapping images captured by the UAV from different locations. Recent developments in deep learning utilize deep convolutional networks to perform this dense pixel correspondence task. A common theme in these developments is to train the network in a supervised setting using available dense 3D reference datasets. However, in this work we propose a novel unsupervised dense point cloud extraction routine for UAV imagery, called UnDER. We propose a novel disparity-shifting procedure to enable the use of a stereo matching network pretrained on an entirely different typology of image data in the disparity-estimation step of UnDER. Unlike previously proposed disparity-shifting techniques for forming cost volumes, the goal of our procedure was to address the domain shift between the images that the network was pretrained on and the UAV images, by using prior information from the UAV image acquisition. We also developed a procedure for occlusion masking based on disparity consistency checking that uses the disparity image space rather than the object space proposed in a standard 3D reconstruction routine for UAV data. Our benchmarking results demonstrated significant improvements in quantitative performance, reducing the mean cloud-to-cloud distance by approximately 1.8 times the ground sampling distance (GSD) compared to other methods.

Методические вопросы комплексной оценки дробящего и техногенного действия взрывных работ при открытой разработке месторождений

Current conditions of mining mineral deposits are characterized with raising requirements towards the environmental consequences of production, as well as increasing volumes of works near settlements, increasing unit capacity of the mining equipment and the volumes of simultaneously blasted rock mass. In this connection the importance of research into the development of energy-efficient technologies of the rock crushing processes and the search for safe methods of their intensification with the minimal harmful effects of large-scale blasting is increasing. The article presents specific methodical features of complex assessment of crushing and man-induced effects of blasting operations in conditions of a test ground and on those of an open pit wall, as well as methodical aspects of calculating the energy spent on seismic action of the blast and air shock wave. The results are provided of systematizing the methods to control the blast seismic action. The results of a comparative assessment of the dust and gas cloud density and its height change in time are discussed with reference to the application of different granulated commercial explosives. A methodological approach is shown to the integrated assessment of the crushing and man-induced effects of blasting operations in open-pit mining.

Analysis of gradient profiles and morphology of the Vela Jr. supernova remnant

We present the study of gradient profiles of the Vela Jr. northwestern rim in X-ray emission and the morphology of this supernova remnant in various spectral ranges of electromagnetic radiation to estimate the distance to the object and its age. In this work were used radiation intensity spatial distributions for the northwestern rim of the supernova remnant RX J0852.0–4622 in the X-ray energy range, 1000.0–2000.0 eV, obtained from measurements of the EPIC-pn camera of the XMM-Newton space observatory for four consecutive time intervals. From the calculated shifts over the period from 2004 to 2018 of the X-ray intensity profiles along the northwestern rim of Vela Jr., limits were obtained on the angular expansion rate of the shock wave of this remnant’s region into a cloud of gas, probably hydrogen: minimum speed Vθmax= 0.29ʺ ± 0.04ʺ year –1 and maximum Vθ60= 0.82ʺ ± 0.11ʺ year –1 .The hydrogen cloud with which the supernova shock wave interacts along the northwestern rim of Vela Jr. is very inhomogeneous. The upper limits for the age of the remnant and the distance to it based on the cloud density estimate are 1920 years and 450 parsecs, respectively. More stringent restrictions on such parameters of RX J0852.0–4622 as its age and distance to it were obtained by analyzing the remnant’s two-ring morphology based on its images in ultraviolet, X-ray, radio and gamma rays: 1190 ± 250 years and 280 ± 60 parsecs.

Detection of Cracks in Ancient Wooden Buildings Based on RPA Oblique Photography Measurement and TLS

ABSTRACTAncient architecture embodies the culmination of historical building techniques and artistic expression, representing a valuable heritage of history, art, and technology. These buildings not only document the cultural traditions and architectural evolution of a nation but also preserve significant aspects of human civilization. However, over time, ancient buildings gradually deteriorate due to both natural and human factors. The issue of cracks is particularly critical in the preservation of ancient buildings. Cracks not only affect the esthetic appeal of these structures, but also, if left unaddressed, they can lead to irreversible damage. Existing technologies struggle to address both the marking of defect locations and the calculation of defect information. For example, image recognition technology can identify cracks in a photo, but it is unable to determine the specific location of the crack within the building, nor can it calculate the three‐dimensional information of the crack. To address this, we combined point cloud technology with crack detection algorithms to develop a novel method. First, we integrated point cloud data acquired from terrestrial laser scanning (TLS) and supplementary remotely piloted aircraft (RPA) data to construct a comprehensive point cloud model of the building for archiving. Next, we conduct point cloud density analysis on the model to extract crack regions based on density variations and then analyze these regions to determine crack locations and compute detailed information. To validate this method, we conducted experiments on a 600‐year‐old wooden building on our campus as a case study. The experimental results indicate that this method can accurately determine the specific location of cracks, with the calculated three‐dimensional information corresponding to their actual positions. This method has also proven to be reliable for continuous annual monitoring, allowing for the ongoing detection and analysis of changes in cracks over time.

Mutual neutralization of C60+ and C60− ions

Context. Mutual neutralization (MN) between cations and anions plays an important role in determining the charge balance in certain astrophysical environments. However, empirical data for such reactions involving complex molecular species have been lacking due to challenges in performing experimental studies, leaving the astronomical community to rely on decades-old models with large uncertainties for describing these processes in the interstellar medium. Aims. Our aim is to investigate the MN reaction C60+ + C60− → C60* + C60 for collisions at interstellar-like conditions. Methods. We studied the MN reaction between C60+ and C60− at collision energies of 100 meV using the Double ElectroStatic Ion Ring ExpEriment (DESIREE) and its merged beam capabilities. To aid in the interpretation of the experimental results, semiclassical modeling based on the Landau-Zener approach was performed for the studied reaction. Results. We experimentally identified a narrow range of kinetic energies for the neutral reaction products. Modeling was used to calculate the quantum state-selective reaction probabilities, absolute cross sections, and rate coefficients of these MN reactions, using the experimental results as a benchmark. We compared the MN cross sections with model results for electron attachment to C60 and electron recombination with C60+. Conclusions. Our results show that it is crucial to take mutual polarization effects, the finite sizes, and the final quantum states of both molecular ions into account in order to obtain reliable predictions of MN rates expected to strongly influence the charge balance and chemistry in environments such as dense molecular clouds.

How do supernova remnants cool?

Context. About 15%-60% of all supernova remnants are estimated to interact with dense molecular clouds. In these high-density environments, radiative losses are significant. The cooling radiation can be observed in forbidden lines at optical wavelengths. Aims. We aim to determine whether supernovae at different positions within a molecular cloud (with or without magnetic fields) can be distinguished based on their optical emission (e.g. Hα (λ 6563), Hβ (λ 4861), [O III] (λ 5007), [S II] (λ 6717, 6731), and [N II] (λ 6583)) using machine learning (e.g. principle component analysis and k-means clustering). Methods. We have conducted a statistical analysis of the optical line emission of simulated supernovae interacting with molecular clouds that formed from the multi-phase interstellar medium modelled in the SILCC-Zoom simulations with and without magnetic fields. This work is based on the post-processing of simulations that have been carried out with the 3D (magneto)hydrodynamic code FLASH. Our dataset consists of 22 simulations. The supernovae were placed at a distance of either 25 pc or 50 pc from the molecular cloud’s centre of mass. First, we calculated optical synthetic emission maps (taking into account dust attenuation within the simulation sub-cube) with a post-processing code based on MAPPINGS V cooling tables. Second, we analysed the dataset of synthetic observations using principle component analysis to identify clusters with the k-means algorithm. In addition, we made use of BPT diagrams as a diagnostic of shock-dominated regions. Results. We find that the presence or absence of magnetic fields has no statistically significant effect on the optical line emission. However, the ambient density distribution at the site of the supernova changes the entire evolution and morphology of the supernova remnant. Due to the different ambient densities in the 25 pc and 50 pc simulations, we are able to distinguish them in a statistically significant manner. Although, optical line attenuation within the supernova remnant can mimic this result depending on the attenuation model that is used. That is why, multi-dimensional analysis of optical emission line ratios in this work does not give extra information about the environmental conditions (ambient density and ambient magnetic field) of supernova remnant.

Stability of compact stars in a uniform density background cloud

We are discussing a scenario where a compact star (neutron star, NS) is embedded in a thin, uniform density background cloud (a remnant cloud after a supernova or a cloud generated from the late stages of a star e.g., a planetary nebula or asymptotic red giant phases) and its effect on the stability of the compact star. Due to the thin background cloud, the spacetime geometry is minimally deformed allowing us to employ the technique of minimal geometric decoupling (MGD). Assuming a uniform background cloud density simplifies the problem, and through the MGD method, one can take Θtt=Θ>0 0$$\\end{document}]]>, where Θ is the density of the cloud. The background cloud interacts with the compact star through a coupling strength α. By varying α, one can tune the cloud density to analyze the stability of the embedded compact star. We found that for α<3×10-5, all the thermodynamic quantities are well-behaved, indicating a stable configuration. Once the coupling parameter exceeds 3×10-5, the adiabatic index drops below Γmax′, triggering a gravitational collapse. Beyond this limit of α, the pressure and speed of sound also become non-physical. At the end, we have used the M-R curve generated from the solution to determine the radii of a few compact stars, namely PSR J1614-2230, PSR J0952-0607, GW190814, and GW200210. Furthermore, we have discussed the possibility of the secondary component of GW200210 i.e. the less massive compact object with an upper mass of 3.3M⊙, which may be a stellar black hole with a Schwarzschild radius RBH=9.746 km. However, if the mass is 2.83M⊙ as observed, then its predicted minimum radius is 10.74 km, corresponding to α=0. This radius is far beyond RBH=8.357 km and therefore is most probably a massive NS in the mass gap.

Regulation of Electron Cloud Density by Electronic Effects of Substituents to Optimize Photocatalytic H2 Evolution of Carbon Dots.

Carbon dots (CDs) have a wide light absorption range, which are promising candidates for photocatalytic water splitting H2 evolution, but they show low activity for hydrogen evolution reaction (HER) due to the slow transfer efficiencies of photogenerated carriers. The electron cloud density of photocatalyst is essential for the separation and migration of photogenerated carriers. In this study, the effect mechanism of electron cloud density regulated by the substituents with different electronic effects on the photocatalytic HER of glucose-based CDs is clarified. CDs-SO3H and CDs-OH are first obtained by introducing electron-drawing group (─SO3H) and electron-donating group (─OH) using a tailoring post-processing strategy. Experimental results show that the H2 yield catalyzed by CDs-SO3H is 89.95 µmol•g-1 in 4 h, which is about four times that of CDs, and 7.4 times that of CDs-OH. The ─SO3H induces a much negative energy band and high electron cloud density on CDs edges, promoting the separation and transfer of photogenerated carriers; while the CDs-OH exhibits a high positive charge density and an upward energy band, hindering the surface complexation of electron-hole pairs and HER. This study will provide an insight into the design of CDs catalysts with efficient photocatalytic HER at a molecular level.

A Low-Cost 3D Mapping System for Indoor Scenes Based on 2D LiDAR and Monocular Cameras

The cost of indoor mapping methods based on three-dimensional (3D) LiDAR can be relatively high, and they lack environmental color information, thereby limiting their application scenarios. This study presents an innovative, low-cost, omnidirectional 3D color LiDAR mapping system for indoor environments. The system consists of two two-dimensional (2D) LiDARs, six monocular cameras, and a servo motor. The point clouds are fused with imagery using a pixel-spatial dual-constrained depth gradient adaptive regularization (PS-DGAR) algorithm to produce dense 3D color point clouds. During fusion, the point cloud is reconstructed inversely based on the predicted pixel depth values, compensating for areas of sparse spatial features. For indoor scene reconstruction, a globally consistent alignment algorithm based on particle filter and iterative closest point (PF-ICP) is proposed, which incorporates adjacent frame registration and global pose optimization to reduce mapping errors. Experimental results demonstrate that the proposed density enhancement method achieves an average error of 1.5 cm, significantly improving the density and geometric integrity of sparse point clouds. The registration algorithm achieves a root mean square error (RMSE) of 0.0217 and a runtime of less than 4 s, both of which outperform traditional iterative closest point (ICP) variants. Furthermore, the proposed low-cost omnidirectional 3D color LiDAR mapping system demonstrates superior measurement accuracy in indoor environments.

Influence of external factors on the success of transmissing messages during the monitoring of wild reindeer movements using the “Argos” satellite system (&lt;i&gt;Rangifer tarandus&lt;/i&gt;)

Currently, satellite telemetry is increasingly in use in environmental research. As a result, researchers obtain a large amount of data on the use of space by animals. However, despite the perfection of modern satellite navigation and data transmission systems, reports on the positions of animals are extremely uneven. We consider here the main technical and natural factors that may influence the success of spacecraft in the “Argos” satellite system receiving messages emitted by radio beacons installed on animals. Among the natural factors when an animal is under the forest canopy, the greatest influence has been established to be exerted by the closure of tree crowns, which can be offset by the abundance of snow in the crowns after heavy snowfalls. Dense clouds have a weaker effect. Of the technical factors associated with the characteristics of flights of satellites of the “Argos” system, the success of receiving messages is influenced, first of all, by the maximum angle of elevation of the satellite above the horizon and the intensity of flights of satellites with a maximum angle of elevation above the horizon of more than 10° per unit time. This is due to the high unevenness of message receipt. At night and in the afternoon, due to a reduction in the number of satellite flights and a decrease in the altitude of their trajectories, the success of reception may decrease to 3% of the number of transmitted messages.

Vibrational and Electronic Spectroscopy of 2-Cyanoindene Cations.

2-Cyanoindene is one of the few specific aromatic or polycyclic aromatic hydrocarbon (PAH) molecules positively identified in Taurus molecular cloud-1 (TMC-1), a cold, dense molecular cloud that is considered the nearest star-forming region to Earth. We report cryogenic mid-infrared (550-3200 cm-1) and visible (16,500-20,000 cm-1, over the D 2 ← D 0 electronic transition) spectra of 2-cyanoindene radical cations (2CNI+), measured using messenger tagging (He and Ne) photodissociation spectroscopy. The infrared spectra reveal the prominence of anharmonic couplings, particularly over the fingerprint region. There is a strong CN-stretching mode at 2177 ± 1 cm-1 (4.593 μm), which may contribute to a broad plateau of CN-stretching modes across astronomical aromatic infrared band spectra. However, the activity of this mode is suppressed in the dehydrogenated (closed shell) cation, [2CNI-H]+. The IR spectral frequencies are modeled by anharmonic calculations at the B3LYP/N07D level of theory that include resonance polyad matrices, demonstrating that the CN-stretch mode remains challenging to describe with theory. The D 2 ← D 0 electronic transition of 2CNI+, which is origin dominated, occurs at 16,549 ± 5 cm-1 in vacuum (6041.8 Å in air). There are no correspondences with reported diffuse interstellar bands.

Shrub height estimation for habitat conservation in NW Iberian Peninsula (Spain) using UAV LiDAR point clouds

ABSTRACT This study aimed to develop and validate a method of estimating 3D parameters from DJI Zenmuse L1 LiDAR on DJI Matrice 300 RTK UAV data to characterise and monitor the structure and conservation status of dense shrub formations. The shrub heights were estimated using Progressive Morphological Filter (PMF) and the Ground Filter module of the FUSION/LDV software. A digital terrain model (DTM) was interpolated with RMSE 0.23 and 0.27 m, respectively, and a normalised canopy height model (nCHM) was calculated by subtracting it from the LiDAR data and the best DTM obtained. The reliability of the estimates was evaluated against georeferenced field data. In addition, the study examined the impact of vegetation characteristics and return reduction in the original point cloud on the accuracy of LiDAR-data derived . Significant differences were found in the correlations between observed and estimated data for the DTM (R2 = 0.9998) and nCHM heights (R2 = 0.51/0.54). The corresponding RMSE values were 0.23 and 0.34 m. Moreover, no significant differences in the reliability were found for different vegetation types, whereas reduction point cloud density (up to 25–50 returns/m2) did not significantly affect accuracy. In conclusion, lightweight UAV LiDAR can effectively detect sub-metric scale vegetation 3D structure, useful for fine-scale habitat conservation.

Possibilities of Using a Virtual Source Model to Refine the Prediction of the Impact of Injurious Effects in Massive Releases of Toxic Gases

Massive leaks of toxic substances occur not only during accidents connected with the operation of industrial enterprises, but also during their transfers by the means of transport. These events pose a serious threat to both people and the environment. Particularly dangerous are situations where dense gas clouds are formed after the release of the given substance. These spread very quickly, while they tend to remain at the earth's surface for a relatively long time and flow into various depressions. In a few minutes, the toxic gas can reach a large area, as confirmed by the conclusions from the Jack Rabbit field tests. Knowledge of the behavior of heavy gas, as well as knowledge of events influencing its dispersion in real conditions, thus provide important information needed for effective management of the resulting accident. The key data is the extent of the harmful effects of the given hazardous substance, which can be obtained by simulating the predicted emergency situation using modeling software (e.g. ALOHA). However, the fundamental shortcoming of this approach is that these software usually generate overestimated results. The fact that dangerous concentrations in the real environment do not reach such distances from the source of leakage has been repeatedly proven by past accidents. The reason for this discrepancy is that the computer programs used do not allow to model with sufficient accuracy all the simultaneous physico-chemical processes that are applied during the dispersion of dense gas clouds. This task is far too complicated and only a part of it can be solved with the necessary precision. However, for the needs of emergency planning, these inaccuracies represent a relatively fundamental limitation. One way how to deal with this problem is to use a virtual resource (sometimes called a virtual point) model. It is successfully used in various areas where it is necessary to simplify the otherwise demanding physical modeling of the temporal and spatial distribution of matter emitted from a surface or volume source. The main idea of a virtual source is that the real primary emission source is approximated to an imaginary source that is located at a different location but acts and appears outwardly as if it were a real source of leakage. The key task of this solution is to determine the parameters of this source, because this is the only way to obtain results with significantly higher reliability during the subsequent simulation of the considered accident scenario.

Low-cost photogrammetry solutions for surveying confined underground spaces: testing the traditional set-up against 360° camera on Tombs of the Kings archaeological site

Abstract. This study explores low-cost photogrammetry solutions for surveying confined underground spaces, focusing on Tomb 7 at the UNESCO World Heritage Site, Tombs of the Kings in Paphos, Cyprus. The research, part of the ENGINEER project, compares traditional photogrammetric methods using frame cameras against a 360° multi-lens camera. The aim is to identify reliable, low-cost methods for 3D documentation of archaeological sites, which can be used for structural analysis and systematic monitoring.Three photogrammetric acquisition methodologies were tested: handheld with frame camera, standard with frame camera, and relaxed with 360° camera. The study evaluates the accuracy of these acquisition methods by comparing dense point clouds generated from each dataset against a reference dataset obtained via terrestrial laser scanning (TLS). Metrics such as cloud-to-cloud distance, roughness, and point cloud density were used for comparison.Results indicate that while the 360° camera offers ease of use and high data density, it also introduces more noise and variability. Traditional methods, though more time-consuming, provide more consistent and accurate results. The findings suggest that combining both approaches could optimize data quality and acquisition efficiency, making the 360° multi-lens camera a viable low-cost photogrammetry option for heritage documentation.