Close-range Photogrammetry Technology Research Articles

COMBINED CLOSE RANGE PHOTOGRAMMETRY AND REMOTE SENSING FOR PHOTOVOLTAIC PARKS EFFICIENCY ANALYSIS

Abstract. The paper presents an innovative approach of combining the methods of close-range photogrammetry and remote sensing in the analysis of the efficiency of photovoltaic parks. A UAV was used to capture the site and close-range photogrammetry technology was used to create orthoimages in the thermal and visible zone. Orthoimages obtained from close-range photogrammetry imagery were combined, and the resulting multichannel image was analysed with remote sensing methods. Spatially overlapping RGB and thermal orthoimages are collocated and a multispectral image was created. Cluster analysis of the multispectral image was performed. Using remote sensing methods, a four-channel multichannel image was created and classified through supervised classification approach with predefined masks. The training data for the classifier represents the types of defects found on the photovoltaic panels. The obtained results were analysed and an assessment of the classification was made.

Monitoring Bridge Dynamic Deformation Law Based on Digital Photography and Ground-Based RAR Technology

Dynamic deflection deformation is a crucial index which can reflect the healthy operation of bridges; due to their limitations, monitoring technologies (e.g., sensors, automatic total stations, and GPS) cannot perform high-frequency and whole-process non-contact dynamic deformation monitoring. Therefore, taking the Jinan Fenghuangshan Road Bridge as an example, this paper developed key low-cost and high-precision close-range photogrammetry technology and combined this with GB-RAR technology to remotely monitor bridge dynamic deformation. The results indicate that the measurement accuracy pertaining to the technology, which is based on an isometric virtual surface, is approximately 0.5 mm when the monitoring distance is 250 m, which can meet the accuracy requirements of bridge deformation monitoring. A vehicle’s dynamic load is transmitted in the form of a stress wave inside the bridge, and with regard to span, the wave is most significant in the 1/2 to 1/4 range. This study observes that the maximum deflection deformation of the bridge is 47.2 mm, which is within the allowable deformation range of the General Specifications for Design of Highway Bridges and Culverts. The research results herein provide technical support and data reference for safety monitoring, and for the reinforcement and maintenance of bridges such as the Fenghuangshan Road Bridge.

Numerical simulation scheme of jointed rock masses using UAV photogrammetry and a disk-based discontinuous deformation analysis model

<abstract><p>The use of unmanned aerial vehicles (UAVs) for photogrammetry allows the rapid acquisition of high-resolution images of geological masses in complex landforms. However, effective analysis of the acquired image information remains a key research issue. At K158 + 837 on the Chongqing-Huaihua Railway, Baima jointed rock masses were reconstructed with high accuracy using UAV close-range photogrammetry technology, and rock discontinuities were extracted from the projected image. The proposed modeling algorithm for jointed rock masses enables the preprocessing of two-dimensional jointed rock mass slopes. Numerical simulations using the disk-based discontinuous deformation analysis method show that the discontinuity network formed by initial cutting significantly affects the subsequent crack development. Meanwhile, simulation results under different scenarios indicate the importance of the pre-reinforcement measures applied to unstable rock masses. The workflow developed based on these results can serve as a reference for the comprehensive acquisition, recognition and numerical modeling analysis of similar jointed rock masses.</p></abstract>

A comparative experimental study of rill erosion on loess soil and clay loam soil based on a digital close-range photogrammetry technology

Accurately describing rill development is important for building physical process models of soil erosion. The objectives of this study were to investigate the evolution processes of rill erosion morphology, their impacts on runoff and sediment yield, and the relationship between flow hydraulic characteristics and rill erosion dynamic mechanisms on slopes of two soil types, namely, clay loam soil (CLS) and loess soil (LS), under two successive rainfall events at a rainfall intensity of 120 mm h−1. We used digital close range photogrammetry technology to obtain overhead images of two experimental soil bins (5 m long, 1 m wide and 0.5 m deep with a slope gradient of 20°) at 5-minute time intervals to monitor the dynamic processes of rill erosion. The results showed that rill erosion processes exhibited important impacts on sediment and runoff and its hydrodynamic characteristics. Compared with LS, runoff formed and rills developed earlier in the CLS slope. Soil with high clay content was more prone to form rills, but less susceptible to severe soil erosion than LS. Once rills began to develop in LS, soil loss increased and the morphology of rills changed rapidly, as did runoff rate. The flow velocity for the two soils decreased gradually with time and increased along the flow direction. The trend of Froude number (Fr) decreased with time, whereas the Darcy-Weisbach resistance coefficient (f) exhibited an opposite trend. The Reynolds number (Re) of LS increased first and then decreased, while Re of CLS decreased gradually with time. Sediment yield and runoff were positively correlated with f, but significantly negatively correlated with Fr. Moreover, Re was significantly negatively correlated with sediment yield, but not with runoff. These results are of great importance for soil loss prediction.

The Dynamic Displacement Monitoring Method Using Unmanned Aerial Vehicles Based on Digital Close-Range Photogrammetry

How to carry out fast and reliable dynamic deformation monitoring of building structures is an important issue for engineers and technicians. Digital close-range photogrammetry technology has the advantages of noncontact, multipoint, and rapid monitoring, and the application of UAVs makes the monitoring task no longer limited by the size of the field, but the current technology can not guarantee the rapid deployment of UAVs in dynamic deformation monitoring, and these methods commonly have higher requirements for image quality, and cannot ensure the stability of accuracy. To this end, we propose a dynamic displacement monitoring method for UAVs based on digital close-range photogrammetry technology and optimize the data processing process for the problem that there is still moving when the UAV hovers. A building with an overhead corridor structure with a large flow of people was selected for the experiment. The experiment used ground digital cameras and drones to monitor separately to compare the monitoring results. The results show that the proposed method is simple and easy to use. The monitoring method can be deployed quickly, which is expected to be applied to emergency monitoring scenarios.

Application of Structural Deformation Monitoring Based on Close-Range Photogrammetry Technology

The problem of structural deformation monitoring has always been a research hotspot in engineering architecture. Research on structural deformation monitoring is the main way to solve the risk of engineering construction. Based on using close-range photogrammetry technology to monitor structural deformation, combining with image recognition technology to collect and process image data, and using the conditions of direct linear transformation and collinear equation to calculate based on the extracted coordinates of the measuring point, finally, according to the coordinates of the measuring point and the deflection value of the bridge structure, the study is carried out. Experiment: first, five sets of data are used to calibrate the close-range photogrammetry equipment of measurement point accuracy are analyzed, then the bridge piers and the measurement point coordinates, the lasso, under different load on the accuracy of close-range photogrammetry technology is analyzed, according to the relevant data of the error of the close-range photogrammetry technology are analyzed, and through the calculation of different measurement methods to analyze the direct linear transformation manifested in the article. The final results show that the X-axis coordinate range of the measured points in the auxiliary spatial coordinate system is 25∼40, Y-axis coordinate range is 8∼36, and Z-axis coordinate range is 10∼35. The coordinates of measuring points of bridge cables are distributed in the fourth quadrant of the spatial coordinate system. The accuracy values of all coordinates of the measuring points under the close-range photogrammetry equipment are less than 0.1 mm, indicating that the close-range photogrammetry equipment has a good effect on the calibration of measuring points, and the error generated when the load action of each measuring point of the bridge cable is 10 N is greater than that generated when the load action is 20 N. In different calculation and measurement methods, the results obtained by total station measurement and calculation method are reduced by about 0.04∼0.07 m compared with the actual value; the results obtained by direct linear transformation method are increased by about 0.02∼0.04 m compared with the actual value; and the results obtained by other measurement and calculation methods are increased by about 0.04∼0.06 m compared with the actual value.

High-precision detection method for large and complex steel structures based on global registration algorithm and automatic point cloud generation

For extremely large and complicated steel structure buildings, the traditional monitoring method is inefficient and labor-intensive. However, LiDAR and UAV close-range photogrammetry can directly collect data in various large and complex environments, register sites, and fit nodes to monitor and analyze their structures. Taking a long-span steel structure monitoring as an example, this paper introduces the deformation monitoring scheme of steel structure with lidar and unmanned aerial vehicle close-range photogrammetry technology. The method of feature-based global registration is adopted to register the site point cloud. The initial value of feature constraint is taken as the error equation of observation value column, and the overall adjustment is carried out. The spatial transformation parameters and unknown point adjustment values are solved through the bundle adjustment model. Through iterative global registration algorithm, the correction error of observation value is controlled within a certain threshold range through constant constraint weighting and reconciliation of observation value until registration is completed, and the entire grid structure is generated. The eccentricity calculation of the spherical node and column in the grid structure is carried out by using the spherical node multi-link center point algorithm. Then, the dense point cloud generated by the photos taken by UAV close-range photogrammetry and the grid structure generated by LiDAR point cloud are used as mutual references, so that the deformation monitoring of long-span steel structures becomes more detailed and comprehensive.

Extraction and statistics of discontinuity orientation and trace length from typical fractured rock mass: A case study of the Xinchang underground research laboratory site, China

The geological parameters of rock discontinuities are of great significance for the evaluation of high-level radioactive waste repository and underground research laboratory (URL) site characteristics. To provide sufficient basis for the construction of the Xinchang URL site, this paper presents a comprehensive set of methods for acquisition of discontinuity parameters. In this set of methods, a high precision three-dimensional point cloud model of an outcrop with real geographic information is established based on close-range photogrammetry technology, from which not only planar discontinuities but also linear discontinuities can be identified and extracted by a semi-automatic method. A new fast-fuzzy clustering method is proposed to cluster discontinuity sets. The statistics method based on topographic window projection is improved to increase the rationality of estimating the geometric characteristics of fracture traces. As a preliminary validation, the results of this case study reveal that these methods have good applicability in acquiring discontinuity parameters, which is also conducive to the establishment of a deterministic-stochastic discrete fracture network (DSDFN) model to further analyze the properties of fractured rock mass. In addition, it is preliminarily found that some outcrops different locations have structures with similar geological features to a certain extent; moreover, the fractures exposed on the outcrop surface have distribution characteristics similar to those in the granite body obtained by drilling. Above all, the presented multidisciplinary methods could provide an alternative and practical approach for low-cost and accurate acquisition of discontinuity parameters, and thus, to study the properties of fractured rock mass effectively.

Unconfined Deformation Characteristics of Collapsed Soil Based on Close-range Photogrammetry Technology

Benggang is a special type of landform type that exists in the hilly areas of tropical and subtropical hills in the south of China. The water and soil erosion occurring on the collapsed land is different from other types of erosion. Its occurrence and development are characterized by uncertainty and rapidity, which seriously threaten the ecological environment and human settlement security. The intrinsic geotechnical characteristics of the soil are a major factor affecting its formation and development. The unconfined compressive test plays an important part in the study of the mechanical properties and failure modes of the soil in the collapsing region. The near-sight measurement technique is now used for the unconstrained resistance. The lateral deformation of the soil samples in the pressure test was sampled and the image information was digitized using matlab. The deformation of the soil with different mechanical properties was analyzed by the displacement information of the marked points and the overall contour deformation and other information. Results showed that in the unconfined compressive strength test, there was no significant difference in the overall deformation of the different soil samples. In one sample, there were significant differences in the displacement of different markers. The close-range photogrammetry technique can well compensate for the lack of the unconfined compression test and it also has a broad space for development in the field of soil and water conservation.

Application of augmented reality and close range photogrammetry technology for mapping of cultural heritage areas (case study: Ai Renung Site, Sumbawa Regency)

The Ai Renung site is the first megalithic complex site on Sumbawa that has 8 sarcophagus objects and has been used as an ancient park by the NTB Provincial Cultural Heritage Preservation Hall. Unfortunately, until now it does not have a cultural heritage map that describes the location and condition of the site, so the presentation of spatial information that describes the location is not conveyed to tourists. In this study, an augmented reality application was made from a combination of 3D model visualization and orthophoto maps. Augmented reality application is implemented on an Android device. Application users can see the visualization of the 3D sarcophagus model virtually using an Android device when scanning one of the markers found on the Ai Renung Site Cultural Heritage Map. This study also analyzes 3D models and orthophoto. The results of the control point analysis on orthophoto, the RMSE value of 0.293 m was produced. Based on the CE90 test of the RMSE value, orthophoto can be used as a base map in making Cultural Heritage Zone Maps with a scale of 1: 1000 and entering into order class 3. As for forming a 3-dimensional model, most 3D model objects have RMSE values that are less than 0.5 m. So that it meets the Level of Detail 3 order criteria.

Passive measurement method of tree diameter at breast height using a smartphone

The accurate measurement of diameter at breast height (DBH) is essential to forest resources inventory, management, and carbon cycle modeling. Monocular vision passive measurement method based on a smartphone is a technique that allows for automatic, portable, and mobile measurement of DBH. Here, we propose a method for measuring the DBH of multiple trees from a single image taken by a smartphone camera, using machine vision and close-range photogrammetry technology. First, we present a visual segmentation approach based on an improved frequency-tuned saliency algorithm, which allows us to extract the trunk contour. Then, we establish a depth extraction model to calculate the depth of each tree. To calculate the DBH of the trees in the image, we establish an adaptive feature coordinate system for DBH measurement of multiple trees, which helps us to study the conversion relationship between the coordinate systems and establish the tree DBH measurement model. Furthermore, the tree DBH measurement model is established based on the rigid motion law between each space coordinate systems; we first establishes the mapping relationship between the pixel coordinate system and the object space coordinate system. Then, according to the depth information, we can obtain the coordinate of the DBH measurement position in the image plane coordinate system, and then derive the diameter at breast height from the image. Experiment results showed that the calculated DBH have a strong relationship with the truth values (RMSE = 0.217 cm). The method yields an average relative error of 2.32% at distances of 2–10 m. For trees with DBH values less than 20 cm, the absolute error is <0.237 cm; for larger trees, the relative error is less than 1.272%. These errors fall within the accuracy requirements of the continuous inventory of Chinese national forest resources.

In-situ non-contact 3D optical deformation measurement of large capacity composite tank based on close-range photogrammetry

Recently, fiber-reinforced composites are widely used in manufacturing of large storage tanks for transportation purposes, thanks to their excellent mechanical and chemical performance, and their good applicability to the shaping of particular geometries. In this contribution, a non-contact 3D optical deformation measurement technique is proposed for monitoring the deformation of carbon-fiber reinforced composite tank subjected to different loading scenarios, which could not be achieved by traditional displacement sensors and resistance strain gauges due to large measuring ranges. This technique is based on the close-range photogrammetry technology, wherein 3D information is extracted from two-dimensional photographs. This is done by positioning artificial reference point markers on the measuring tank before loading, and calculate the 3D coordinates of these markers through analyzing the group photos captured in each loading stage. By tracking and comparing the 3D coordinates of the point markers among different loading stages, the 3D deformation of the tank is obtained. The loading tests comprise both hydrostatic pressure and water-pressurizing tests. The performed in-situ measurements show that the proposed technique can fulfill the efficiency and accuracy requirement of deformation measurement in tank loading tests. This in turn significantly contributes to better understanding the mechanical response at the macroscopic scale, thus improving safety performance.

A videogrammetric system for measuring the full-field blade deformation of a heavy-duty helicopter's rotating rotor.

In this paper, a videogrammetric system, based on three-dimensional digital image processing and industrial close range photogrammetry technology, is proposed to solve the three-dimensional motion and deformation parameters of a rotating blade by identifying a speckle pattern. For the high aspect ratio and flexible rotor blade design often used in heavy-duty helicopters, there are extremely complex aerodynamic, dynamic, and coupling problems that require solutions to measure the full-field deformation of the rotating blade in the test condition of a rotor test tower. The key issues involved include a two-step calibration method using separate internal and external parameters for a large field of view, and a reliable estimation of the seed point method for a large deformation and weak correlation speckle images match. The system was developed and a simulation test was conducted on a rotor test tower. The results show that the proposed system is practicable to measure the surface displacement and motion parameters of a high-speed rotating rotor blade.

THREE-DIMENSIONAL MAPPING OF AN ANCIENT CAVE PAINTINGS USING CLOSE-RANGE PHOTOGRAMMETRY AND TERRESTRIAL LASER SCANNING TECHNOLOGIES

Abstract. The paper describes the used of close-range photogrammetry and terrestrial laser scanning technologies as an innovative technology for acquiring the three-dimensional data of an ancient cave paintings. The close-range photogrammetry technology used in the research was divided in two categories which are the UAV-based close-range photogrammetry and the terrestrialbased close-range photogrammetry. The UAV-based technology involved with the used of calibrated Phantom 4 System while the terrestrial-based technology involved with the calibrated Sony F828 digital camera and pPhotoModeler software. Both stereo and convergent image acquisition techniques were used to acquire the images of the paintings. The ancient cave paintings were also recorded using terrestrial laser scanning technology. In the research, the FARO Focus 3D terrestrial laser scanner was used to capture the three-dimensional point clouds and images of the paintings. The finding shows that both close-range photogrammetry and laser scanning technologies provide excellent solutions to map and to record the ancient paintings. As compared to the conventional method, both close-range photogrammetry and terrestrial laser scanning technology provide a noncontact solution for data acquisition and the data was recorded in digital format for better protection and security.

A Method of Metro Tunnel Deformation Measurement Based on the Theory of Close Range Photogrammetry

In order to solve the difficulties in the deformation measurement of subway shield tunnel structure, a non-contact measurement method of close range photogrammetry technology based on movable base is put forward. A light metal frame is designed as the movable base, which is calibrated by the electronic total station. And the case study verified the feasibility of the measurement.

Strain Measurement for Sheet Metal Forming Based on Close Range Photogrammetry

To improve efficiency and automation of the 3D full-field surface strain measurement for sheet metal forming, a new grid strain measuring scheme was developed based on the close-range photogrammetry technology. A Local Canny Detector algorithm was proposed for grid nodes and coded targets detection. A 10-parameters nonlinear camera model and the bundle adjustment algorithm were used to optimize the calibration parameters. A multi-epipolar constraint method was employed for grid node matching. Finally, the surface strains were calculated according to the changes of the grid sizes. To evaluate the performance of the proposed scheme, a stamping forming experiment was conducted. Experimental results show that the scheme can provide a non-contact, intuitive and effective solution for strain measurement in sheet metal forming process.

Development of a 3D Full-Field Monitoring System for Large-Scale Static Deformation Based on close Range Photogrammetry

A non-contact deformation measurement method is proposed for monitoring the 3D full-field static deformation of large-scale structures under loads, which could not be achieved by traditional displacement sensors and resistance strain gauges. This method is based on the close range photogrammetry technology. By tracking and comparing the 3D coordinates of the targets between different epoch, the load–deformation diagram in 3D form for the whole large-scale structure is obtained, which is valuable for further mechanical behavior analysis. Real-scale power transmission tower experiment shows that the proposed method can fulfill the efficiency and accuracy requirement in large-scale full-field deformation monitoring task

Performance Dynamic Tracking and Analysis System of Road Traffic Signs

In view of the heavy workload and possible intervention to the normal traffic flow during the performance testing of road traffic signs, this paper is designed to present a system that can be installed in an automobile and automatically track and analyze the performance of traffic signs. The system consists of a carrying vehicle, GPS, IMU, area-array cameras, frame grabbers, data acquisition software and data analysis software. Based on close-range photogrammetry technology, the system is designed with a set of effective road traffic signs automatic detection algorithms, which can automatically measure and analyze the properties of road traffic signs, such as dimensions, headroom and verticality of the column, etc.

Large field-of-view deformation measurement for transmission tower based on close-range photogrammetry

The loading capacity of transmission towers cannot be calculated accurately only by finite element analysis (FEA) method. Traditional displacement sensors and strain gauges are not suit due to larger measuring range. In this paper, a novel system based on close-range photogrammetry technology (CPT) is proposed for tracking the 3D deformation of transmission tower during loading test. Artificial markers are pasted on the deformation area before loading. The 3D coordinates of these markers are reconstructed by using CPT methods at each stage, and the coordinate systems of different stages are registered together by means of global transformation points. The whole field 3D deformation under different load level is then obtained by tracking the homonymous markers among different stages. It is helpful for further analysis of the failure mechanism and mechanical properties of steel structures. The effectiveness of the proposed system is demonstrated by retrieving a full-scaled transmission tower deformation during loading test. A feasible solution for improving the load carrying capacity of the tested transmission tower is discussed. Evaluation experiment results indicate that the proposed method could achieve accuracy of 0.1 mm/m.

Rapid three-dimension optical deformation measurement for transmission tower with different loads

A transmission tower is a form of highly indeterminate space structures used extensively. A non-contact optical deformation measurement method is proposed for monitoring the deformation of transmission tower during loading test, which could not be achieved by traditional displacement sensors and resistance strain gauges. This method is based on the close range photogrammetry technology. Paste the artificial markers on the deformation area before loading, and calculate the 3D coordinates of these markers through analyzing the group photos captured in each step. By tracking and comparing the 3D coordinates of the markers among different steps, the load–deformation diagram in 3D form for the whole transmission tower is obtained. It is helpful for further mechanical behavior analysis. Acceptance experiment results indicate the accuracy of this method could reach about 0.1 mm/m. Real-sized model experiment shows that the proposed method can fulfill the efficiency and accuracy requirement of deformation measurement in transmission tower loading test.