Ground-based Laser Scanning Research Articles

Ground laser scanning of the flyover through the railway for the purposes of its reconstruction

The article presents the possibility of obtaining geometric parameters of an flyover passing through a railway using ground–based laser scanning technology using modern equipment Leica Scan Station C10. The practical significance of using the chosen method lies in the fastest and most convenient scanning of the object, reducing production costs and, of course, high accuracy of the spatial data obtained necessary for the reconstruction of the flyover. A study of the use of ground-based laser scanning technology to obtain spatial data of the flyover was conducted, as a result of which the advantages of the chosen method were revealed. Also, based on the data obtained, a comprehensive three-dimensional model and two-dimensional drawings were prepared, such as the facade of the flyover, its plan and drawings of transverse profiles. Thanks to the compiled drawings and models of the bridge structure passing through the railway, the design work on the reconstruction of the facility has become much easier and more efficient. The presented experience confirms the need to introduce modern technologies, namely ground-based laser scanning in survey activities in order to develop and detail design solutions for the reconstruction of flyovers.

3d model of Medova cave, Lviv

The purpose of this article is to present and provide a detailed analysis of the 3D model of the Medova Cave in Lviv, created using laser scanning technology. The main objectives include revealing the accuracy and detailing the obtained model, as well as determining its potential applications in various fields such as geological research, scientific exploration, cultural heritage, and tourism. Additionally, the article aims to emphasize the importance and advantages of using laser scanning for creating precise and realistic 3D cave models, opening new possibilities for the study and preservation of natural unique formations. Method. The article describes the methodology used to create a 3D model of the Medova Cave, which involves several key steps. Firstly, a thorough reconnaissance of the cave is conducted to identify technical and logistical aspects such as temperature, humidity, movement restrictions, and lighting that are necessary for the scan. Next, ground-based laser scanning is employed, proving effective in conditions of complete darkness and limited space, to ensure accurate data collection regarding the cave's geometry. Reflective markers are strategically placed inside the cave before scanning, facilitating efficient scanning and alignment of scans. Specialized equipment such as GNSS receivers (Trimble R7) and ground-based laser scanners (Faro Focus 3D 120) are utilized for data collection. Software tools like Faro Scene are used for stitching together scans into a unified 3D point cloud model during data processing. Finally, the accuracy of marker connections is analyzed to ensure high-quality registration, and the 3D model is constructed. Detailed 3D models, including textured models and cross-sections for visualizing the internal structure of the cave, were constructed using software such as Move. Results. The research on the Medova Cave, employing ground-based laser scanning, yielded an accurate and detailed 3D model of the cave. This model opens new perspectives for geological and geomorphological studies, tourism development, and cultural heritage preservation. The use of advanced scanning technologies allowed for a comprehensive representation of the cave's geometric features, considering its complex structure and varied dimensions. Scientific novelty and practical significance. The creation of the 3D model of the Medova cave using laser scanning signifies progress in cave geometry studies. The innovation lies in the utilization of advanced laser scanning technologies to ensure a detailed representation of the cave's geometric features, accounting for its complex structure and diverse dimensions. The novelty also lies in the development of a data collection and processing strategy in conditions of complete darkness and limited cave space, resulting in an accurate and realistic 3D model. Practically, the 3D model of the Medova Cave serves as a crucial tool for geological and geomorphological research and the exploration of unique natural formations. The model opens new opportunities for tourism development, where virtual cave exploration can provide a unique experience for visitors. Creating this 3D model is a significant step in preserving and documenting cultural heritage, contributing to the scientific and cultural development of the region, and providing access to unique objects for researchers and the public.

Unfolding WWII Heritages with Airborne and Ground-Based Laser Scanning

Considering how difficult it is for a pin in the ocean to be found, painstaking searches among historical documents and eyewitness accounts often end up with more unknowns and questions. We developed a three-tier geo-spatial tech-based approach to discover and unfold the lost WWII heritage features in the countryside of Hong Kong that can be applied in other contexts. It started with an analysis of historical texts, old maps, aerial photos, and military plans in the historical geographic information system (HGIS) Project ‘The Battle of Hong Kong 1941: a Spatial History Project’ by Hong Kong Baptist University to define regions/points of interest. Then, 3D point clouds extracted from the government’s airborne LiDAR were migrated to form a digital terrain model (DTM) for geo-registration in GIS. All point clouds were geo-referenced in HK1980 Grid via accurate positioning using the global navigation satellite system—real-time kinematics (GNSS-RTK). A red relief image map (RRIM) was then used to image the tunnels, trenches, and pillboxes in great detail by calculating the topographical openness. The last tier of the tech work was field work involving ground validation of the findings from the previous two tiers and on-site imaging using terrestrial LiDAR. The ground 3D LiDAR model of the heritage feature was then built and integrated into the DTM. The three-tier tech-based approach developed in this paper is standardised and adopted to streamline the workflow of historical and archaeological studies not only in Hong Kong but also elsewhere.

RATES OF MODERN DENUDATION OF A SMALL CATCHMENT IN THE MIDDLE MOUNTAIN BELT OF THE GREATER CAUCASUS (CASE STUDY OF THE GITCHE-GIZHGIT CATCHMENT)

The volumes of loose-clastic material moved by modern earth surface processes were quantified for a small mid-mountain catchment area ( F = 1,86 km2), located in the Baksan River basin using a number of independent methods (modeling of erosion and geomorphologic mapping). The total volume of removed material was estimated through the assessment of the thickness of bottom sediments accumulated in a reservoir located in the outlet section of the catchment area. The rates of linear and rill erosion have been found using the results of repeated UAV surveys and the pin method. The rates of rockfall processes are estimated on the basis of repeated ground-based laser scanning. Additionally, published data on the rates of earth surface processes in the mountains were used. Based on the results of field mapping and interpretation of space images, a map of the spatial pattern of leading earth surface processes was compiled. A digital terrain model of the catchment was constructed on the basis of detailed UAV survey. The volume of loose clastic material delivered to the reservoir was estimated using data on the average annual rates of leading earth surface processes, a map of their distribution over the catchment area, and the connectivity index. It has been established that the average annual denudation rate within the catchment area is 0,16 mm/year. At the same time, only about 3-10% of the products of denudation are delivered to the reservoir. The sediment yield, calculated on the basis of the volume of sediments in the reservoir, is 514 t/km2 per year. It is comparable to the sediment yield of small rivers draining the mid-mountain belt of the Alps with similar bedrock lithology, which was calculated using the results of long-term observations of water and sediment discharge at gauging stations.

Моделирование объектов трубопроводного транспорта по данным дистанционного зондирования

The author considers the results of geospatial modeling of a production facility based on data from various types of surveys obtained during monitoring. The essence is to combine it in a single coordinate space for subsequent modeling with remote methods. The technological solutions are described; they enable performing geospatial modeling of pipeline transport objects on the basis of a single coordinate space due to the data from various types of remote studies. The site of the oil refinery, where reconstruction must have been carried out, was chosen as the object of the research. The remote sensing data were obtained through ground-based laser scanning and digital aerial photography using a drone. A scheme for remote sensing, information preprocessing and geospatial modeling of pipeline transportation facilities is provided. As a methodological basis for geospatial modeling, constructive methods are used, assuming the finiteness of the elements and the use of its basic components as an information unit.

StrucNet: a global network for automated vegetation structure monitoring.

Climate change and increasing human activities are impacting ecosystems and their biodiversity. Quantitative measurements of essential biodiversity variables (EBV) and essential climate variables are used to monitor biodiversity and carbon dynamics and evaluate policy and management interventions. Ecosystem structure is at the core of EBVs and carbon stock estimation and can help to inform assessments of species and species diversity. Ecosystem structure is also used as an indirect indicator of habitat quality and expected species richness or species community composition. Spaceborne measurements can provide large-scale insight into monitoring the structural dynamics of ecosystems, but they generally lack consistent, robust, timely and detailed information regarding their full three-dimensional vegetation structure at local scales. Here we demonstrate the potential of high-frequency ground-based laser scanning to systematically monitor structural changes in vegetation. We present a proof-of-concept high-temporal ecosystem structure time series of 5 years in a temperate forest using terrestrial laser scanning (TLS). We also present data from automated high-temporal laser scanning that can allow upscaling of vegetation structure scanning, overcoming the limitations of a typically opportunistic TLS measurement approach. Automated monitoring will be a critical component to build a network of field monitoring sites that can provide the required calibration data for satellite missions to effectively monitor the structural dynamics of vegetation over large areas. Within this perspective, we reflect on how this network could be designed and discuss implementation pathways.

Tree attribute assessment in urban greenwood using ground-based LiDAR and multiseasonal aerial photography data

Advances in LiDAR and unmanned aerial vehicle technology have made high-resolution data available, which can be used for individual tree detection and assessing tree attributes. The accuracy of these assessments is still not clear for stands with high tree species diversity as well as leaf-off and leaf-on conditions. The aim of this study was to assess the quality of tree top detection and individual tree heights extracted from photogrammetric point clouds and canopy height models as well as ground-based LiDAR clouds in mixed and coniferous forest stands depending on the phenological stage. The study has been carried out in the Botanical Garden of the Petrozavodsk State University (Republic of Karelia, Russia). Four flight missions (in 2019–2021) using Phantom 4 Pro quadcopter were conducted in the arboretum (> 200 tree species) during periods of leafless, leaf biomass growth, full foliage and autumn leaf colouration. A single ground-based laser scanning was performed using a Leica BLK 360. Multiseasonal ultra-high resolution orthophoto mosaics (1.1–2.8 cm/pixel), photogrammetric point clouds (average density is 4200 points/m2), as well as LiDAR clouds (11 600 points/m2) were obtained. Further analysis was performed on three sites differing in tree species composition, tree density and site area. Tree tops were automatically detected from photogrammetric point clouds and their heights were estimated using R environment software. We found that most of the trees (78.9%) were correctly detected by algorithms based on photogrammetric data collected in periods of full foliage and autumn colouration. We also found that the number of false positive (FP) and false negative (FN) cases increased with decreasing in green biomass on deciduous trees. Compared with an average value, tree detection quality increased by 9.4% for coniferous trees with cone-shaped crowns (Abies sibirica, A. balsamea, A. fraseri, Picea abies, P. pungens, P. omorika, Pseudotsuga menziesii, Larix sibirica) regardless of the tree density, and tree detection quality decreased by 10% for coniferous trees with an ellipsoidal-shaped crowns (e.g. Thuja occidentalis, genus Pinus) or in cases for broad-leaved trees with high tree density. The lowest value of tree detection quality (F = 0.49) was found for the leafless period. High values (F = 0.84) obtained for periods of full foliage and autumn colouration indicates that tree detection quality was well in general. For the biomass growth period, this value (F = 0.69) also indicates a high quality of tree detection results. We also found that tree heights estimated using photogrammetric data well matched with tree heights measured on LiDAR clouds (R2 = 0.99). The highest accuracy was obtained for coniferous trees with cone-shaped crowns. We also estimated the height increments of different tree species between 2019 and 2021 based on photogrammetric point clouds. The highest annual height increment was obtained for Pinus sibirica (52 cm), and the lowest for Pseudotsuga menziesii (32 cm). Overall, our results have shown the potential to use photogrammetric and LiDAR data for tree mapping and estimating tree attributes in multi-species forest stands of arboretums or urban parks, as well as in natural forests.

Simulation on Different Patterns of Mobile Laser Scanning with Extended Application on Solar Beam Illumination for Forest Plot

Light detection and ranging (LiDAR) technology has become a mainstream tool for forest surveys, significantly contributing to the improved accuracy of forest inventories. However, the accuracy of the scanned data and tree properties derived using LiDAR technology may differ depending on the occlusion effect, scanning configurations, various scanning patterns, and vegetative characteristics of forest plots. Hence, this paper presents a computer simulation program to build a digital forest plot composed of many tree models constructed based on in situ measurement information and two mobile scanning patterns, i.e., airborne laser scanning (ALS) and ground-based mobile laser scanning (MLS). Through the adjustment of scanning parameters and the velocity of vehicle loading LiDAR sensors, the points scanned using two scanning patterns were compared with the original sampling points, derived from the constructed digital forest plots. The results show that only 2% of sampling points were collected by LiDAR sensors with the fastest vehicle speed (10 m/s) and coarsest scanning angular resolution (horizontal angular resolution 0.16° and vertical angular resolution 1.33°), and approximately 50% of sampling points were collected by LiDAR sensors with slow vehicle velocity (1.25 m/s) and a finer scanning angular resolution (horizontal angular resolution 0.08° and vertical angular resolution 0.33°). Meanwhile, the potential extended application of the proposed computer simulation program as a light model of forest plots was discussed to underpin the creation of the forest digital twin. Three main conclusions are drawn: (1) the collected points from airborne laser scanning (ALS) are higher than those collected from ground-based mobile laser scanning (MLS); (2) reducing the vehicle velocity is more efficient at improving the high density of the point cloud data than by increasing the scanning angular resolution; (3) the lateral extension of crown area increasing the light beams’ receptor area and the clumped leaf dispersion augmenting the light penetration with vertical elongation are the two paramount factors influencing the light transmittance of tree crowns.

The Sukil River valley: a natural geological laboratory (case studies from the Ukrainian Carpathians)

Abstract In this chapter we present a brief geological description of the Sukil River valley, which is located in the Ivano-Frankivsk region in the western part of Ukraine, and the interesting geological features found there. Here, different types of rocks are exposed over a small area. The area is rich in various structural features such as joints, small faults, and different types of folds, duplexes and clastic dykes. Two outcrops of folds found in the Cretaceous deposits in the village of Bukivets are unique geosites. In addition, in the city of Bolekhiv, there are the ruins of a saltery. We describe the types of research conducted in this natural laboratory, most of which concerns structural geology. Geological phenomena are studied using both classical approaches and the latest technologies. Electronic compasses were used widely in the study of mesostructures. For the first time, balanced geological sections have been constructed for the territory of the Ukrainian Carpathians both for outcrops and for the entire Sukil River valley. Ground-based laser scanning was used for the detailed mapping of folds in Bukivets. Subsequently, the exposure was studied using unmanned aerial vehicle (UAV) photogrammetry, which was used to construct virtual geological outcrops that can be used widely for educational purposes. The urgency for creating virtual tours became apparent during the COVID pandemic. These models were also used to create the ‘Geo-Carpathians’ project, a Polish–Ukrainian geotourism route through the Carpathian Mountains. These models can be also used to assist in the teaching of the structural geology of the Carpathians, in the geological training of Earth Sciences students, in excursions for different types of Ukrainian and international conferences, for high-school students, and, indeed, for anyone interested in geology.

Оперативный геодезический контроль деформаций призабойной зоны при инновационных технологиях проходки туннелей

Purpose: To consider the issue on performance of operational control of deformations of tunnel bottomhole zone with the use of ground-based laser scanning technology when tunneling with New Austrian tunneling method which is the most progressive one and feasible in economics terms for underground building construction by mining. The essence of this method is in that as a support for tunnel bottom-hole zone, a self-supporting shell made of sprayed concrete without traditional fastening method usage is applied that allows to save time for tunneling significantly, especially of those tunnels which have complex geometry and non-standard dimensions. At the same, the conceptual basis for this method is the necessity to identify operatively bottomhole zone soil mass deformations that’s justified by the need to provide job realization safety. Methods: As a major method for to determine tunnel bottomhole zone geospatial position it is proposed to consider ground-based laser scanning technology. Scanning result processing was implemented in specialized software package Leica Cyclone 3DR. Results: Existing experience of geodetic check of deformations in tunneling by New Austrian method is considered. Processing results for data on ground laser scanning of a tunnel separate fragment are presented, a tunnel mathematical three-dimensional model is obtained and assessment of deviations of tunnel actual surface from obtained theoretical one is fulfilled. Practical significance: The obtained threedimensional model can be further used for geodetic monitoring of deformations. Theoretical bases for estimation required accuracy for deformation characteristics definition are substantiated which are based on the transition from construction tolerances to average quadratic errors of deformation characteristics definition and then to average quadratic errors of coordinates for laser scanning points. The enlarged stages of scanning are defined with view of tunneling technology of New Austrian method.

Інвентаризація об’єктів садово-паркового господарства скверу Т. Масарика м. Ужгород із використанням НЛС

Goal. The aim of the work was to show the main stages and prospects of analysis of the obtained data of ground laser scanning of small groups of green areas of cities on the example of T. Masaryk Square in Uzhgorod, as well as to compare this technology with the classical method of inventory of green areas..Method. The paper highlights the features of the inventory of garden and park facilities using ground-based laser scanning (NLS). The method of not only determination of existence of objects of green economy but also their characteristics is offered. The inventory of green plantations and the results of its application are described on the example of T. Masaryk Square in Uzhhorod. A comparison of inventory data collected by analog methods in 2017 and NLS data in 2021. Inventory of green plantations is carried out in accordance with the Instruction on technical inventory of green plantations in cities and towns of Ukraine every five years from April to October and provides: determination of the total area occupied by green facilities, including trees, shrubs , flower beds, lawns, trails, etc .; determination of the number of trees and shrubs by types of plantings, species, age, diameter at a height of 1.3 m of tree trunks and the state of their content; determining the value of the object as a whole and its individual areas; timely introduction of changes that have taken place in green areas, in drawings, passports of green facilities and summary data on green areas of the settlement. During the inventory, the following was carried out: determination of the total area occupied by green facilities, including trees, shrubs, flower beds, lawns, paths, etc .; determination of the number of trees and shrubs by type of plantings, species, age, diameter at a height of 1.3 m of tree trunks and the state of their maintenance; determining the value of the object as a whole and its individual areas; timely introduction of changes that have taken place in green areas, in the drawings, passports of green facilities and summary data on greenery of the settlement. Results. As a result of the research, a laser scan of T. Masaryk Square in Uzhhorod was performed and the obtained data were processed. A detailed inventory of greenery on the Independence Embankment, namely on the territory of the memorial square. Masaryk. After sub-tree accounting, 106 tree species of different species were studied. Conifers – 3 species, deciduous – 12. During the inventory of sanitary conditions, the following number of trees in each category: I category -49; II category – 33; III category – 1; IV category – 27; V category – 1. The general sanitary assessment of plantings is satisfactory with insignificant drought and emergency plantations of white poplar that need to be replaced.. Practical value. The obtained results can be used by the municipal authorities to tidy up and take care of T. Masaryk Square in Uzhhorod.

Remote Sensing Techniques for Bridge Deformation Monitoring at Millimetric Scale: Investigating the Potential of Satellite Radar Interferometry, Airborne Laser Scanning and Ground-Based Mobile Laser Scanning

Remote Sensing Techniques for Bridge Deformation Monitoring at Millimetric Scale: Investigating the Potential of Satellite Radar Interferometry, Airborne Laser Scanning and Ground-Based Mobile Laser Scanning

ГЕОДЕЗІЯ, КАРТОГРАФІЯ І АЕРОФОТОЗНІМАННЯ

The aim of this work is to develop an algorithm for mathematical three-dimensional modeling of a typical roof of a Ukrainian church based on ground-based laser scanning and to find ways to optimize the model depending on the input data set. Method. The accuracy of the simulation depends on the laser scan data. The number of points obtained and their accuracy will affect the final result - 3D model of the roof. Given the typical design of the church roof in the shape of a cone, you can apply the standard mathematical algorithm for modeling part of the buildings of a typical church. Result The proposed algorithm was developed in the MathCad software environment. 3D scanning materials of the Ukrainian typical church were used to develop the mathematical algorithm. The algorithm analyzes the location of the scanning points of the church roof and performs its averaging. As a result of the algorithm, erroneous measurements were rejected and a model of the part of the roof was obtained, which forms the optimal geometry of the structure. Scientific novelty and practical significance. The proposed mathematical algorithm allows to automate some modeling processes of a typical Ukrainian church for design decisions. This method of modeling can be used for similar structures of other buildings.

Microgeophysics and geomatics data integration reveals the internal fracturing conditions of the statue of Ramses II (Museo Egizio, Torino, Italy)

The combined acquisition of 3D ultrasonic tomography and radar scans is growing for cultural heritage diagnostics. Both methods proved to be efficient in the detection and location of fractures and weaknesses within the investigated artefacts. Although the two techniques are widely applied together, an integrated approach for data interpretation is still missing. We present the results of radar and ultrasonic prospections carried out on the statue of the young Ramses II, an absolute masterpiece of the Egyptian art preserved in the collection of the Museo Egizio of Torino (Italy). Geophysical results are incorporated within the 3D model of the statue retrieved from total station measurements, ground-based and handheld laser scanning. A data integration approach is then proposed for the joint interpretation of the geophysical results, exploiting the final ultrasonic velocity model and radar attribute analysis (i.e. local dissimilarity computation) to define a combined damage index. The proposed methodology is efficient in fracture detection and location and improves the readability of the final results also for non-expert geophysical interpreters, offering guidance to the museum for preservation and restoration of the masterpiece.

The use of laser scanners in geodetic support of the construction of mining industrial enterprises

Currently, in the design and construction of large industrial enterprises, three-dimensional BIM models of buildings and structures are being introduced. This article describes the practical application of the Leica RTC360 terrestrial laser scanner at the industrial site of PJSC Uralkali, Berezniki, Perm Territory, under construction. The purpose of the survey is geodetic monitoring of construction and the implementation of as-built documentation for the sections of heating, ventilation, water supply, sewerage and heating networks of the shaft building No. 2. To bind point clouds to the construction coordinate system and heights, linear-angular networks are created inside existing industrial enterprises using an electronic total station to determine the coordinates and heights of marks for a ground-based laser scanner. The article considers an automatic method and method for registering the best approximation for combining point clouds obtained using NLS with BIM models. As a result, the automatic method is used when there is a building coordinate system on the object under study. The method of registering the best approximation is used when there is only a conditional coordinate system, for example, for control assemblies of metal structures. It is proposed to perform automatic classification of point clouds, both inside industrial facilities and outside. The classification process is based on a machine learning algorithm that relies on calculations using a video card. Ground-based laser scanning was used directly at a real mining enterprise under construction, which allows further geodetic monitoring, creation of as-built documentation and timely detection of deviations from the project using BIM models.

Survey monitoring of the enclosing dam № 1 of the «GRES Topar» LLP ash dump by the terrestrial laser scanning method

To determine the state of stability of the enclosing dam №1 of the ash dump of «GRES Topar» LLP, a geodetic monitoring project was developed. The methodology of geodetic observations is based on the use of ground-based laser scanning. An observation station was laid on the local section of the dam, which consists of 3 reference points and 5 working reference points. The displacement is determined by calculating the vector distance from the reference point to each working reference point. The vector distance is determined from each reference point in the same way. For control, a total station survey was carried out, made in non-reflective mode. The convergence of the results did not exceed 2 mm. Geodetic monitoring consisted of 3 series of observations. According to the data obtained, the stable condition of the hydraulic structure was revealed.

Geomechanical monitoring of pit edge massif deformations of open-pit coal mines on ground-based laser scanning

The laser scanning method, used in combination with traditional mine surveying observations, is one of the most effective and safe ways to conduct surveying and instrumental observations on deforming areas of open-pit mining facilities. The article presents the results of ground-based laser scanning of the “Haranutsky” coal pit and performs a comparative analysis to determine the deformations and displacements of the open pit side for different periods, which was performed in the RISCAN PRO environment. Digital Relief Models (DRM) were constructed to distinguish the observation cycles by colors. Based on the results of the monitoring, it was concluded that no critical displacements and deformations were detected, despite the places of small scree deposits in the rock massif, and further systematic observations were recommended.

The geodetic monitoring of deformations of a high-rise building using ground-based laser scanning technology

The article justifies the use of laser-scanning systems for geodetic monitoring of high-rise buildings and structures. Contemporary methods allow solving comprehensively the main tasks of geodetic monitoring. During the monitoring of high-rise objects, not only the main geometric parameters of the objects should be taken into account. The main importance should be given to the mutual arrangement of individual building elements, which is especially important for identifying and predicting deformation processes. Laser scanning coordinate measuring systems are designed to measure the object coordinate points to determine the object's geometric dimensions. The principle of GLS operation is to measure the point coordinates in space by the polar method. Distance is measured by a laser rangefinder using a pulse method with signal digitization technology. The advantage of this approach is a smaller amount of time spent on the creation of a primary survey network. At that, the laying of scanner ray paths is most effective when carrying out ground-based laser scanning of linear structures. But it is advisable to apply its construction elements within the framework of the developed methodology. The development and implementation of new technologies for geodetic work performance, supported by an appropriate level of automation, is always carried out to reduce the time required for data collection and processing. The RiSCAN PRO program is a project-oriented product, i.e. the entire volume of data obtained as a part of a single measurement project is structured and stored according to the RiSCAN PRO project structure.

АНАЛИЗ ДЕФОРМАЦИЙ И НАПРЯЖЕНИЙ ОБОЛОЧКИ ВЕРТИКАЛЬНЫХ СТАЛЬНЫХ РЕЗЕРВУАРОВ ПО ДАННЫМ ЛАЗЕРНОГО СКАНИРОВАНИЯ

The article considers a new technology of measurements of vertical steel tanks (ground-based laser scanning), which delivers a huge volume of unstructured information. There has been carried out a review of existing methods for solving tasks of tank walls' defomations determinations on laser reflec-tion point cloud. It is noted that the accuracy of laser scanning and scans' stitching is sufficient for tank walls' defomations determinations. The existing methods are implemented basically through building irregular triangular surfaces of tank shell on which then surface profiles are built manually or semi-automatically and the defomations are determined and compared to tolerance values. The au-thors suggest a method and algorithm for processing laser reflection point cloud, which by means of several infiltrations by height, radius tolerance and inclinations and interpolation by collocation meth-od is drawn to a rectangular topologically equivalent grid. These allow by several orders to decrease the information volume stored in the database, and regular grid model structure allows to apply numer-ical calculation method for calculating strains occurring in the tank walls. The strains are determined on semi-momentless theory for cylinder shell calculation. The method and algorithm are implemented in geodetic subsystem of automatic system of technical maintenance and repairs of equipment on the oil processing plant. The suggested method will allow in the future to move from normative assess-ment of technical tank state to the assessment on actual strains, which gives objective assessment of tank state for making substantiated decision on the prolongation of its exploitation, current mainte-nance and repair.

Лазерное сканирование и аэро- фотосъемка с БПЛА в исследовании структуры лесотундровых древостоев Хибин

Studying the structure of stands is a key point in assessing the role of trees in carbon deposition. Information on the spatial structure of ground vegetation at the upper treeline is still insufficiently presented in modern studies. High resolution remote sensing can provide important data to understand the properties and dynamics of vegetation in these conditions. We test the applicability of ground-based mobile laser scanning of the terrain and aerial photography for the rapid and high-precision assessment of the characteristics of tree stands in the forest-tundra ecotone. We obtained canopy height models (CHMs) of the forest and supplemented them with aerial photographs of the research area on the southeastern slope of the Khibiny Mountains. Using CHMs we have delineated boundaries of tree crowns. The height and projection area were determined for each tree. The first characteristic obtained by laser scanning was compared to the heights of the same trees estimated by field measurements. This was done for the purposes of verification. The comparison revealed that laser scanning data allow to set heights closest to field measurements in case the heights are determined by the maximum values of brightness of pixels of CHMs with manual correction of values when outliers are detected (R2 = 0.84). Since manual correction of outliers is time-consuming, we proposed a way to automate the measurements by determining tree heights using the sum of the average value of pixel brightness and the standard deviation multiplied by 2.5 (R2 = = 0.79). We compared the area characteristics of the stands obtained by laser scanning and the unmanned aerial vehicle (UAV) photography. Thus, we obtained detailed information on the spatial location and size of 4424 trees in an area of about 10 ha and compared the results of measuring tree characteristics obtained by different methods. It was also found that with increasing height from 290 to 425 m above sea level on the studied slope, the average height of stands decreases gradually from 4.5–5.0 to 1.1–1.6 m with small fluctuations (0.2–0.4 m), while the density of stands changes from 4620–5860 to 145 m2/ha in a non-linear way.