Zhihua Xu

China University of Mining & Technology (Beijing), Beijing, China · College of Geoscience and Surveying Engineering

Pile inventory is a common practice in terrestrial laser scanner applications. However, there are two main challenges when using the traditional terrestrial laser scanning (TLS) for pile inventory. One is the high cost and the other is the unreachability problem within a limited space. This letter develops a cost-effective system combining two sing...

The registration of terrestrial point clouds is a crucial technique to obtaining the entire scene geometry. However, urban scenes, characterized by repetitive components, symmetrical structures, and object occlusion, pose ambiguity challenge of matches in the accurate registration of terrestrial point clouds. This paper proposes a coarse registrati...

Structure-from-Motion (SfM) techniques have been widely used for 3D scene reconstruction from multi-view images. However, due to the large computational costs of SfM methods there is a major challenge in processing highly overlapping images, e.g. images from unmanned aerial vehicles (UAV). This paper embeds a novel skeletal camera network (SCN) int...

The 4-points congruent sets (4PCS) techniques have widely been used for global registration of point clouds in terrestrial laser scanning (TLS) applications. Nevertheless, due to many 4PCS methods adopt a downsampling strategy in the collection of correspondences; it is challenging to obtain a real congruent set of tuples in different point clouds...

Terrestrial laser scanning (TLS) techniques have been widely used in open-pit mine applications. It is a crucial task to measure the exploitative volume of open-pit mines, within a specific time interval. One major challenge is posed, however, when conducting accurate registrations for temporal TLS surveys in continuously changing areas, created by...

It is necessary to timely and accurately estimate the surface deformations in mining areas, especially the three-dimensional (3D) deformations during surface movement. At present, nearly all mining-induced 3D deformations retrieved by interferometric synthetic aperture radar (InSAR) pertain to the SAR imaging interval. Research on progressive 3D de...

Point clouds of large-scale urban street scenes contain large quantities of object categories and rich semantic information. The semantic segmentation is the basis and key to subsequent essential applications, such as digital twin engineering and city information model. The global feature of point clouds in large-scale scenes can provide long-range...

The settlement (or subsidence) of mine waste dump is likely to cause landslides, thereby imposing threats on the safety of human beings and other local properties. Hence, it is essential to accurately predict the settlement for the early-warning of settlement-induced geohazards. Traditional mechanical methods require in situ mechanical parameters a...

Structure-from-motion (SfM) techniques have been widely used for 3D scene reconstruction from sequential video frames. However, for reconstructing narrow and confined spaces such as the interior of drainage pipes, selecting geometrically optimal frames is a major challenge not only to reduce the number of needed frames but also to yield better geom...

Pile inventory is a common practice in terrestrial laser scanner applications. However, there are two main challenges when using the traditional TLS for pile inventory. One is the high cost and the other is the unreachability problem within a limited space. This letter develops a cost-effective system combining two single-pulse scanners and a range...

Social distancing protocols have been highly recommended by the World Health Organization (WHO) to curb the spread of COVID-19. However, one major challenge to enforcing social distancing in public areas is how to perceive people in three dimensions. This paper proposes an innovative pedestrian 3D localization method using monocular images combined...

Stochastic gradient descent and other adaptive optimization methods have been proved effective for training deep neural networks. Within each epoch of these methods, the whole training set is involved to train the model. In general, large training data sets have data redundancy among their training samples. In this paper, we present an algorithm to...

The efficient separation of coal and gangue in the mining process is of great significance for improving coal mining efficiency and reducing environmental pollution. Automatic detection of coal and gangue is the key and foundation for the separation of coal and gangue. In this paper, we proposed a hierarchical framework for coal and gangue detectio...

Due to errors in sensors and positioning, there exist mismatches between different phases of mobile laser scanning point clouds, which impedes the application of point cloud, such as changing detection, deformation monitoring, etc. To rectify such mismatches, we designed a 3D deep feature construction method for point cloud registration. The propos...

This article presents an effective classification method for earthquake damage mapping from unmanned aerial vehicles (UAV) photogram-metric point clouds. The classification method consists of three main components: (a) construction of a point feature descriptor regarding to spectral, textural, and geometrical features, (b) optimization of collectin...

This paper investigates the synergetic use of unmanned aerial vehicle (UAV) and terrestrial laser scanner (TLS) in 3D reconstruction of cultural heritage objects. Rather than capturing still images, the UAV that equips a consumer digital camera is used to collect dynamic videos to overcome its limited endurance capacity. Then, a set of 3D point-clo...

The image sequences from an unmanned aerial vehicle (UAV) are used to calculate the engineering volume (overburden amount, stacking amount, etc.) of open-pit mine. Firstly, two sets of video frames or optical images of the open-pit mine are collected with a time interval using a portable digital camera installed on an octocopter. Next, two groups o...

Many methods have been developed to detect damaged buildings due to earthquake. However, little attention has been paid to analyze slightly affected buildings. In this letter, an unsupervised method is presented to detect earthquake-triggered “roof-holes” on rural houses from unmanned aerial vehicle (UAV) images. First, both orthomosaic and gradien...

The rapid and accurate large scene 3D reconstruction technique from multi-view images can provide important and reliable information for emergency response and disaster assessment. Against the low efficiency of Structure from Motion (SfM) algorithm, this paper develops an image Topology based Structure from Motion (TSfM) algorithm referring to imag...

No single sensor can acquire complete information by applying one or several multi-surveys to cultural object reconstruction. For instance, a terrestrial laser scanner (TLS) usually obtains information on building facades, whereas aerial photogrammetry is capable of providing the perspective for building roofs. In this study, a camera-equipped unma...

There is no single sensor can acquire the complete information for disaster monitoring. This study investigates the applicability of registering multiple point clouds obtained from unmanned aerial vehicle (UAV) images and terrestrial laser scanning (TLS). Low attitude images with high overlaps were collected by an eight-rotor UAV platform and image...

This study utilizes the unmanned aerial vehicle (UAV) to acquire high resolution images for feature matching, resulting in a point cloud. A progressive morphological filter is used to filter out nonground object points from point cloud. Multi-scale and different shape filter windows are adopted for the morphological filter to achieve good performan...

This study investigates the usability of low-attitude unmanned aerial vehicle (UAV) acquiring high resolution images for the geometry reconstruction of opencast mine. Image modelling techniques like Structure from Motion (SfM) and Patch-based Multiview Stereo (PMVS) algorithms are used to generate dense 3D point cloud from UAV collections. Then, pr...

This study was performed aiming to construct the scene geometry with a large set of unmanned aerial vertical (UAV) collections. By improving the popular structure from motion (SfM) algorithm, we focus on the efficiency improvement on procedures of both feature detection and image matching. Distinctive features are firstly detected with a CUDA based...

We address the problem of efficient image matching for large, highly redundant photo collections with highly complex topologies, such as photos acquired by unmanned aerial vehicles (UAV), focusing on disaster monitoring. Our approach conducts a skeleton graph which simplifies the image topology with the consideration of image importance and topolog...

Triangular Irregular Network (TIN), especially Constrained Delaunay Triangular Irregular Network (CD-TIN), has been proven to be more accurate for the modeling of complex urban terrain, compared with raster represented digital elevation model (DEM). DEM with high precision is of importance to simulate urban flood inundation. In the paper, the trian...

We address the problem of efficient image matching for large, highly redundant photo collections with highly complex topologies, such as photos acquired by unmanned aerial vehicles (UAV), focusing on disaster monitoring. Our approach conducts a skeleton graph which simplifies the image topology with the consideration of image importance and topolog...