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Highlights • LiDAR was used to measure the overall deformation of a steel walled structure. • Strain measurement model represented shapes using a high order polynomial function. • LiDAR results were verified in comparison with measured strain gauge data. Abstract Strain measurement in structures provides key information for structural health monitoring (SHM); therefore, researchers have developed various sensing methods for measuring strain in structures. Recently, light detection and ranging (LiDAR) has been studied as a non-contact strain measurement method (NCSMM). LiDAR is a technology for remotely acquiring high precision three-dimensional (3D) coordinate information for a terrain or a structure using a 3D laser scanning system. In recent years, LiDAR applications have expanded to include systems used to monitor structural behavior. Using this technology, structural behavior can be monitored without directly attaching sensors to the surfaces of target structures. It is advantageous to use non-contact 3D laser scanning measuring methods to obtain the 3D coordinates of a specific region or the shape of the target structures. LiDAR technology does not have some of the limitations associated with existing types of measuring sensors used for SHM. Therefore, in this study, we will present a method for estimating deformation and strains for a whole structure by measuring discretized 3D coordinate data of the target structure obtained from the LiDAR. The 3D coordinate data was revised using a regression analysis, and the strain was estimated by developing a finite element model based on the corrected 3D coordinate information. The experimental structural model is a steel plate, which is the primary material used for the outer wall construction of LNG storage tanks. The estimated strains will be compared to the measured values from real strain gauges, and the applicability of the proposed strain measurement method to structural behavior monitoring will be verified. [ABSTRACT FROM AUTHOR]

Purpose – Disaster risk reduction (DRR) technology sharing has emerged as an important global issue across national boundaries. As a result, the DRR technology-sharing environment needs strengthening based on the findings of difficulties in sharing, investment, and commitment. The purpose of this paper is to three fold: first, it will clarify that a web-based platform is the best conduit for linking DRR technology from the supplier to the beneficiary developing countries. Second, it will find the most evolutionary path based on Korean case studies. Finally, it will make recommendations for the efficient implementation of a web-based platform for DRR technology sharing. Design/methodology/approach – This paper posits that DRR technology sharing is a necessary part of enhancing resilience to disasters in the Asia-Pacific region. The evolution of web-based approaches (a merchandise display-type platform, a journal-type platform, an electronic market-type platform, and an architecture and governance-type platform) and an actual case of space technology sharing providing support for an evolution toward community-based technology sharing in DRR. The research will find the most efficient way going forward based on the case study of a four-year R & D project sponsored by the South Korean Government. It will also find the success factors for the way to establish and operate the platform efficiently and effectively through case studies of the four types of web-based platforms. Findings – Sharing of DRR technology through a web-based platform among Asia-Pacific countries is necessary in order to equip all parties with essential technology to mitigate intensifying disasters, to overcome the barriers of technology sharing, to breakdown transfer issues due to language barriers, and to strengthen insufficient DRR budgets. Among the four types of web-based platforms, the architecture and governance-type platform proved to be the most effective and efficient. In addition, four principles for an efficient implementation are identified through case studies, analysis, and research. Originality/value – This paper reports on the reasons why it is difficult for DRR technology sharing in the Asia and Pacific regions and suggests a web-based DRR technology-sharing platform as a solution for the region. Moreover, it substantiates that the architecture and governance platform type as the most efficient and effective evolution with four principles: develop based on end-user’s needs; take a problem-solving approach; contain interactive communication tools; and provide business opportunity. [ABSTRACT FROM AUTHOR]

This paper presents an image matching technique for IKONOS satellite imagery based on rational function models (RFMs). This algorithm adopts the object-space approach and reduces the search space to within the confined line-shaped area called the piecewise matching line (PML). Also, the detailed procedure of generating 3D surface information using the RFM coefficients (RFCs) is introduced to illustrate an end-user's point of view. The final digital elevation model (DEM) generated using the proposed scheme shows a mean error of 2·2 m and rmse of 3·8 m compared with that from a 1:5000 scale digital map. [ABSTRACT FROM AUTHOR]

We demonstrate a new technique to automatically map the margin of ice sheets using ERS-1 SAR and SPOT imagery. The technique relies on a series of image processing techniques including edge enhancement, dynamic thresholding, region growing, edge detection, and edge following. The mapping technique is used to measure temporal displacement of the ice sheet margin north and south of the Jakobshavn Glacier in Greenland. During the 4 year interval between 1988 and 1992 we find ice sheet margin advance/retreat rates of about +/- 12m/year, consistent with independent observation. We combine the 1988 and 1992 data to assign an average ice margin location for the observation interval assuming a constant displacement rate. The resulting snapshot of the ice sheet margin can be used as a benchmark for future change detection studies. In both cases the uncertainties are better than 200m. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) and safety assessment are very important areas for evaluating the behavior of structures. Various wired and wireless sensors can measure the physical responses of structures, such as displacement or strain. One recently developed wireless technique is a light imaging detection and ranging (LiDAR) system that can remotely acquire three-dimensional (3D) high-precision coordinate information using 3D laser scanning. LiDAR systems have been previously used in geographic information systems (GIS) to collect information on geography and terrain. Recently, however, LiDAR is used in the SHM field to analyze structural behavior, as it can remotely detect the surface and deformation shape of structures without the need for attached sensors. This study demonstrates a strain evaluation method using a LiDAR system in order to analyze the behavior of steel structures. To evaluate the strains of structures from the initial and deformed shape, a combination of distributed 3D point cloud data and finite element methods (FEM) was used. The distributed 3D point cloud data were reconstructed into a 3D mesh model, and strains were calculated using the FEM. By using the proposed method, the strain could be calculated at any point on a structure for SHM and safety assessment during construction. [ABSTRACT FROM AUTHOR]

• Holistic approach is the key for the resilience of cultural assets and heritage. • Implementing a resilient system requires the integration of various types of knowledge. • Digital cultural heritage cube is built on the basis of space, time, and sensor axis. • It enables timely access to any desired information, improving the resilience of cultural heritage. • After applying the digital cultural heritage cube to cultural properties in Korea, the damage to culture assets can be minimised and their resilience can be enhanced. Recent developments in geospatial information technology have prompted researchers to utilise geospatial information for decision making in disaster situations. Cultural properties should be preserved because they reflect the local characteristics and knowledge of their creators. Therefore, damaged cultural properties, which are difficult to restore, should be among the first considerations in a disaster situation. In this paper, we propose a method for using geospatial information to promote cultural heritage resilience with respect to disasters. Images from satellites, drones, and terrestrial sensors are available in various forms and provide various types of information. The acquired data can be formed into a digital cultural heritage cube, which enables timely access to any desired data. Additional information can be derived from the accumulated data through image fusion processes and the ancestors' knowledge encapsulated in cultural properties. To verify this, we explored two disasters—arson and forest fires—in Korea. We concluded that, if the proposed method is applied to cultural properties, the damage to culture assets can be minimised and their resilience can be enhanced. [ABSTRACT FROM AUTHOR]

• The suitability of utilizing the MMS point cloud as GCPs in low-cost UAV-based photogrammetry was analyzed. • The geolocation accuracy of the photogrammetric point clouds was the highest when GCPs diversely distributed in the vertical direction. • The oblique images allowed for a detailed 3D reconstruction of building facades and improved vertical geolocation accuracy of point cloud. • The enhanced point cloud was generated by merging the low-cost UAV-based photogrammetric point cloud and the MMS point cloud. The accurate and dense reconstruction of high-quality 3D spatial information is essential for digital twin-based smart cities. Unmanned aerial vehicle (UAV)-based photogrammetry allows the 3D modeling of urban environments in the shortest possible time. Accurate georeferencing is a prerequisite for utilizing geospatial information. The geolocation accuracy of real-time kinematic (RTK)/post-processing kinematic (PPK) UAV-based photogrammetry is significantly high; however, RTK/PPK UAVs are costly. In contrast, the geolocation accuracy of low-cost UAV-based photogrammetry is generally low. It can be improved by indirect georeferencing using ground control points (GCPs) obtained in situ; however, this requires significant amounts of human resources and time. Therefore, this study analyzes the suitability of utilizing the mobile mapping system (MMS) point cloud as GCPs for low-cost UAV-based photogrammetry. We checked the significance of the vertical distribution of GCPs on the geolocation accuracy of low-cost UAV-based photogrammetry using the feature points of building facades (captured via vehicle-based MMS along roads) as GCPs. In addition, typical UAV-based photogrammetry only uses nadir images, which limits the detailed 3D reconstruction of building facades. In this study, a detailed reconstruction and an improved vertical geolocation accuracy were achieved using oblique images. Experiments demonstrated that the geolocation accuracy of the low-cost UAV-based photogrammetric point cloud improved to within 16 cm in the X-, Y-, and Z-directions. It was at its highest when the GCPs were diversely distributed in the vertical direction. Finally, we generated an enhanced point cloud by merging the low-cost UAV-based photogrammetric point cloud and the MMS point cloud. [ABSTRACT FROM AUTHOR]

The annual or seasonal fluctuation of glacier calving fronts has been carefully mapped and measured, due to this property's close correlation with overall glacier behavior. For that purpose, remote sensing data is the most useful tool; however, LANDSAT-7 ETM+ images, a popular dataset, has been losing parts of its data since May 2003, due to a scan line corrector (SLC) failure of the ETM+ sensor. Therefore, calving front mapping with later LANDSAT-7 ETM+ data requires interpolation or pre-processing. To overcome these issues, we present a novel approach based on line-buffering in a GIS (Geographic Information System) environment. In applying this method to a time-series of the Jakobshavn Isbræ's glacier front position in West Greenland, we proved this approach to be more objective and robust than alternative methodologies; its shape similarity measure, moreover, was shown to be highly useful. Additionally, a simulation series was carried out, which established that the buffering-based method successfully estimated, with high objectivity, both mean displacement and shape similarity from a pair of calving fronts delineated from the SLC-off data without any modification. Further analyses of Jakobshavn Isbræ based on the buffering-based approach revealed that the frontal advance during a winter season preceding a period of high rates of retreat fails to balance the recession of the previous summer. Moreover, based on analyses of the shape similarity of sequential calving fronts, it was determined that a rapid retreat is likely accompanied by a significant change in calving front shape. [ABSTRACT FROM AUTHOR]

Highlights: [•] This paper proposes a semi-automatic method for 3D building reconstruction with segmentation and boundary tracing phases. [•] It addresses that fully-automated 3D modeling from terrestrial LiDAR data is not practical in real-world applications. [•] Traced building boundaries provide better interpretation and data reduction. [•] Remaining points after segmentation and boundary tracing were converted to 3D mesh for detailed manual modeling. [•] Results show that the proposed method improves modeling productivity and facilitates operators’ accurate object drawing. [ABSTRACT FROM AUTHOR]

The extent of glacier terminus displacement is instrumental in investigations of natural or artificial geographic changes. Its importance to earth science and engineering is reflected in the considerable efforts that have been devoted to the development of several boundary displacement analysis methods. Among the methods, the buffering-based approach compares favorably with other approaches in objectivity and robustness. However, it does not consider the relative positions of boundaries, because its buffering operation cannot determine features' relative directions. This limitation incurs inaccurate calculation results – underestimation of mean shifts and overestimation of shape variations, especially when the two compared boundaries intersect. Discrete displacement analysis (DDA), an alternative method that considers given geographic objects as a set of a finite number of points, is proposed here. In a series of tests carried out, including Jakobshavn glacier's calving front, DDA was found to correctly calculate mean shift and shape variation even in cases where the conventional buffering-based method failed. Moreover, this approach is independent of the dimension of space in which it is implemented, and thus is expected to be utilized for analysis of 3D geographic object displacement. [ABSTRACT FROM AUTHOR]

• Digital images were used to evaluate the cable tension force of cable-stayed bridges. • Cable tension evaluation method is based on digital image processing and parabolic cable theory. • Cable tension results measured from Digital images were verified in comparison with measured lift-off test data. Cable tension is a critical variable for evaluating the structural health and safety of cable-stayed bridges. Although various vision-based systems have been developed for measuring the tension of cables, it is still cumbersome to measure the instantaneous tension of cables, which fluctuates owing to external loadings such as temperature and wind. Therefore, in this paper, a method for evaluating the tension and range of tension using multiple digital images is proposed. A field test was conducted on cables of a real cable-stayed bridge to confirm the applicability and reliability of the proposed method. The cable tension evaluated using the image was compared with the value measured directly through lift-off tests, and the tension evaluated was consistent with that measured directly. The proposed method can provide a time- and cost-effective option for determining the instantaneous cable tension force of cable-stayed bridges compared to existing tension measurement systems. [ABSTRACT FROM AUTHOR]

Abstract: Satellite radar altimetry has been extensively used to estimate ice-sheet elevation change rates over Antarctica and Greenland from repeated measurements of surface elevation changes through either crossover or collinear (repeat-track) analysis. However, there has been no attempt to use satellite radar altimetry over mountain glaciers because the instrument often loses lock or does not provide usable measurements over the rough terrains and steep slopes due to its large footprint size. In this study, we demonstrate the feasibility of satellite radar altimetry to estimate elevation change rates over the Bering Glacier System in Alaska for the period of 1992–2010 from TOPEX/Poseidon and Envisat radar altimeter measurements. We are able to observe the 1993–1995, and 2008–2011 surge events from the T/P and Envisat time series, respectively. We also observe the accelerated elevation decreases in 2002–2007, after slightly negative or near nil elevation changes in 1996–2001, which are related to the temperature and snow depth variations. Our method can be applied to other wide (>7km) glaciers worldwide, and provide new insights into the behavior of glaciers responding to climate change. [Copyright &y& Elsevier]

A large amount of information needs to be identified and produced during the process of promoting projects of interest. Thermal infrared (TIR) images are extensively used because they can provide information that cannot be extracted from visible images. In particular, TIR oblique images facilitate the acquisition of information of a building's facade that is challenging to obtain from a nadir image. When a TIR oblique image and the 3D information acquired from conventional visible nadir imagery are combined, a great synergy for identifying surface information can be created. However, it is an onerous task to match common points in the images. In this study, a robust matching method of image pairs combined with different wavelengths and geometries (i.e., visible nadir-looking vs. TIR oblique, and visible oblique vs. TIR nadir-looking) is proposed. Three main processes of phase congruency, histogram matching, and Image Matching by Affine Simulation (IMAS) were adjusted to accommodate the radiometric and geometric differences of matched image pairs. The method was applied to Unmanned Aerial Vehicle (UAV) images of building and non-building areas. The results were compared with frequently used matching techniques, such as scale-invariant feature transform (SIFT), speeded-up robust features (SURF), synthetic aperture radar–SIFT (SAR–SIFT), and Affine SIFT (ASIFT). The method outperforms other matching methods in root mean square error (RMSE) and matching performance (matched and not matched). The proposed method is believed to be a reliable solution for pinpointing surface information through image matching with different geometries obtained via TIR and visible sensors. [ABSTRACT FROM AUTHOR]

In unpredictable disaster scenarios, it is important to recognize the situation promptly and take appropriate response actions. This study proposes a cloud computing-based data collection, processing, and analysis process that employs a crowd-sensing application. Clustering algorithms are used to define the major damage types, and hotspot analysis is applied to effectively filter critical data from crowdsourced data. To verify the utility of the proposed process, it is applied to Icheon-si and Anseong-si, both in Gyeonggi-do, which were affected by heavy rainfall in 2020. The results show that the types of incident at the damaged site were effectively detected, and images reflecting the damage situation could be classified using the application of the geospatial analysis technique. For 5 August 2020, which was close to the date of the event, the images were classified with a precision of 100% at a threshold of 0.4. For 24–25 August 2020, the image classification precision exceeded 95% at a threshold of 0.5, except for the mudslide mudflow in the Yul area. The location distribution of the classified images showed a distribution similar to that of damaged regions in unmanned aerial vehicle images. [ABSTRACT FROM AUTHOR]

Road information high definition maps (HD map) contain information about the facilities around the roads and are often constructed through a mobile mapping system (MMS). Although constructing an HD map is essential for road maintenance and the application of autonomous driving in the future, it is problematic to acquire the data of objects other than the facilities in an unstructured form while operating the MMS. In this study, the researchers define this object data as clutter objects and present a method of automatic removal using characteristics of the MMS and image segmentation techniques. By applying the method to 10 KITTI (Karlsruhe Institute of Technology and Toyota Technological Institute at Chicago) datasets, clutter objects were removed with an average overall accuracy of 91% with 0% (0.448%) error of commission for the complete point cloud map. [ABSTRACT FROM AUTHOR]

This paper proposes a technique to estimate the distance between an object and a rolling shutter camera using a single image. The implementation of this technique uses the principle of the rolling shutter effect (RSE), a distortion within the rolling-shutter-type camera. The proposed technique has a mathematical strength compared to other single photo-based distance estimation methods that do not consider the geometric arrangement. The relationship between the distance and RSE angle was derived using the camera parameters (focal length, shutter speed, image size, etc.). Mathematical equations were derived for three different scenarios. The mathematical model was verified through experiments using a Nikon D750 and Nikkor 50 mm lens mounted on a car with varying speeds, object distances, and camera parameters. The results show that the mathematical model provides an accurate distance estimation of an object. The distance estimation error using the RSE due to the change in speed remained stable at approximately 10 cm. However, when the distance between the object and camera was more than 10 m, the estimated distance was sensitive to the RSE and the error increased dramatically. [ABSTRACT FROM AUTHOR]