Table of Content

25 May 2022, Volume 0 Issue 5

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Review on the development of surveillance video and geographic information fusion technology

HAN Shijing, MIAO Shufeng, HAO Xiangyang, CHEN Runze

2022, 0(5):  1-6.  doi:10.13474/j.cnki.11-2246.2022.0132

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Surveillance video plays an important role in the security and management of smart and safe cities. Although, the video data has the characteristics of real-time, intuitive, and rich, the coupling analysis ability with geographic information is insufficient. The spatial information of the video itself cannot be effectively utilized. At the same time, due to the shortcomings of poor real-time and slow update of geographic information, it cannot reflect the dynamic scenes. In order to achieve better results, many scholars and industry personnel at home and abroad comprehensively consider their advantages and research the fusion of surveillance video and geographic information. This paper introduces the key technologies of the fusion of surveillance video and geographic information, analyzes the research status and application fields of the fusion, and finally points out the possible development trend in the future based on the bottlenecks and difficulties encountered.

Research status and progress of slope stability monitoring methods in open-pit mines

CHEN Lanlan, XIA Yiqiang, XIAO Haiping, LIU Xiaosheng

2022, 0(5):  7-13.  doi:10.13474/j.cnki.11-2246.2022.0133

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Slope stability monitoring is an important means to effectively prevent landslides. Based on the summary of domestic and foreign literature, this paper analyzes the applicability and shortcomings of slope stability monitoring methods from different technical means and different application scope. The monitoring technology has realized the transformation and development from point to surface, from slope surface to slope interior, from manual measurement to automatic and intelligent monitoring, from close monitoring to remote monitoring. In view of the problems existing in the slope stability monitoring technology, this paper puts forward the viewpoints of adopting the integrated monitoring of space, sky and earth, implementing the multi-source monitoring data fusion, and the integrated interaction of stability dynamic evaluation and remote monitoring, so as to improve the reliability of slope stability early warning and the timeliness of remote monitoring, and provide important reference for reducing the production cost of the mine and ensuring the safe implementation of the mine. It also provides reference for the research in related fields.

A method for extracting dynamic threshold value of water body information in Beibu Gulf coastal area

REN Chao, DENG Shiqin, GAO Maofang

2022, 0(5):  14-19,37.  doi:10.13474/j.cnki.11-2246.2022.0134

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Accurate acquisition of water body distribution information and water body variation patterns is of great importance in the comprehensive management of watersheds. Based on the ocean water index (OWI), the correlation between OWI and the normalized difference vegetation index (NDVI) was analyzed based on the spectral characteristics of the water body. The method is based on the dynamic equilibrium of the two indices, and a dynamic threshold method with high stability is proposed and experimentally validated. The experimental results show that the dynamic threshold method can extract water body information stably and accurately, avoiding the error of artificially set thresholds, and the proposed index has good universality for both domestic high resolution images and the rest of optical images, which can be applied to the monitoring of coastal coastline.

A multi-band combination water index model based on Landsat 8

WANG Chunxia, ZHANG Jun, LI Yixu, FAN Chengcheng

2022, 0(5):  20-25.  doi:10.13474/j.cnki.11-2246.2022.0135

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In this paper, by analyzing the spectral difference between the visible light band and the near-infrared band in the Landsat 8 data, the visible light band in the Landsat 8 data is taken as one group, and the near-infrared band and the mid-infrared band are taken as another group, and a multi-band combination water index (MBCWI) model is constructed. Based on Landsat 8 data, water extraction experiments were carried out in Hefei, Ankang and Kangding areas with a total of 3 scene data and 5 different scenarios. The results show that the model can not only suppress the influence of clouds, shadows, bare soil, bright-colored ground objects and buildings on water extraction, but also can extract water containing a large number of cyanobacteria well, and the threshold is stable, and the Kappa coefficient is better than 0.968 5, the overall accuracy is as high as 99.69%, and the overall error is less than 8.92%. Compared with other water indices, the extraction accuracy is significantly improved.

Flood extent extraction method based on the texture features of GF-3 images

YU Zongqiao, WANG Yuhong, LIU Wensong, ZUO Yufang, FENG Feng

2022, 0(5):  26-31.  doi:10.13474/j.cnki.11-2246.2022.0136

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Flood disaster will cause huge losses to local society and economy, timely and rapid monitoring of flood range is of great significance in disaster relief. Synthetic aperture radar (SAR) can provide support for all-day, all-weather and large-scale flood monitoring due to its active microwave imaging mechanism. This paper takes GF-3 satellite images as data source, and extracts 138 image texture features of GF-3 based on six texture description methods, such as the gray level co-occurrence matrix (GLCM) and the local binary pattern (LBP), etc. Then, the texture features with high importance scores are selected for water information extraction by using the index importance evaluation function of the random forest (RF) algorithm. Finally, the initial water extraction results are post-processed combined with mathematical morphology to evaluate the flood disaster near Chaohu Lake in Anhui province. The experiments show that the water extraction accuracy of the proposed method is better than the results of traditional threshold method (Otsu) and classification (KNN and SVM) algorithms. And the proposed method can effectively extract the influence range of flood disaster, and provide a reference for selecting appropriate texture features of SAR images for rapid monitoring of flood range.

Extraction method and accuracy evaluation of typical lake water body in Hoh Xil region based on GF-6 WFV data

WANG Renjun, LIU Baokang, DU Yu'e, ZHANG Hongli, YU Zhiyuan

2022, 0(5):  32-37.  doi:10.13474/j.cnki.11-2246.2022.0137

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Lakes are sensitive indicators of climate change. It is of great significance to obtain lake water information quickly and accurately for the study of regional climate change and the protection and governance of regional ecological environment. According to the characteristics of GF-6 WFV satellite image data, four lakes at different locations in Hoh Xil area are selected as the research objects, and uses single-band method,band difference method and normalized difference water index(NDWI) water body information extraction in four lakes. The data obtained by visual interpretation are used as real ground data to evaluate the accuracy of different water body extraction methods. The results show that the results of single band method is easily affected by shallow water body, but less affected by snow, while band difference method and NDWI method are greatly affected by snow. Although NDWI can effectively extract shallow water body, it is still affected by lake bottom sediments to a certain extent. Compared with single band method and NDWI method, band difference method can effectively distinguish shallow water bodies and background features.

Multi-Patch multi-frame incremental traffic video object detection method based on YOLO v4

WEN Nu, GUO Renzhong, HE Biao, WAN Yuan

2022, 0(5):  38-44.  doi:10.13474/j.cnki.11-2246.2022.0138

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Improving the generalization ability of object detection model is a research focus and key issue in the field of computer vision. This paper proposes a Multi-Patch method and a multi-frame incremental prediction strategy to improve the robustness of traffic video object detection in different scenarios, and effectively solve the problem of low object recall ratio in videos caused by variable object scales. According to the video resolution and object size, the video frame is automatically divided into the best input size based on the Multi-Patch method, the YOLO v4 neural network is used to correlate the context information of the continuous frame, and the incremental prediction strategy is used to reduce the missed detection rate of the video object detection, and to improve the detection confidence score and recall rate of video object in different scenarios. Collect traffic videos under different shooting conditions to verify the effectiveness of the algorithm. Experimental results show that the object detection method proposed in this paper has a recall rate of more than 80% and an average confidence score of more than 0.84.

Using GRACE/GRACE-FO time variable gravity field data to quantify the characteristics of drought events in the Yangtze River basin

CUI Lilu, HE Mingrui, ZHANG Cheng, ZOU Zhengbo, WANG Xiaolong

2022, 0(5):  45-48,55.  doi:10.13474/j.cnki.11-2246.2022.0139

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Aiming at the problem of accurate quantification the characteristics of regional drought event, a drought event assessment approach based on GRACE/GRACE-FO time variable gravity field is proposed in this paper. And the drought index based on GRACE/GRACE-FO data is validated using traditional drought indices. Finally, this approach is used to detect the drought events that occurred in the Yangtze River basin form April 2002 to December 2020 and quantify the characteristics of these drought events. The results show that the drought index in this paper has good consistent with the traditional drought indices, and there are eight major drought events in the Yangtze River basin during the study period, the most serious of which lasts 23 months from September 2002 to July 2004. The drought severity is -14.07 and an average of 40% of basin area has been affected by drought in this event.

Research on the temporal and spatial changes of vegetation coverage in Qinling mountains based on Google Earth Engine platform

ZHAO Kan, SHI Yun, NIU Minjie

2022, 0(5):  49-55.  doi:10.13474/j.cnki.11-2246.2022.0140

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The dynamic change of vegetation cover in Qinling mountains has an important impact on its ecological environment. Based on the Google Earth Engine cloud platform, this paper selects the Landsat TM/OLI surface reflectance data from 1986 to 2019, combines with the dimidiate pixel model to estimate the fractional vegetation cover (FVC) in Qinling mountains. The spatiotemporal variation, stability and persistence of FVC are analyzed by using the slope of interannual variation, coefficient of variation and Hurst index. In addition, the coupling relationship between FVC and temperature and rainfall is explored,and the impact of land use change on FVC is analyzed. The results shows that:during the 34 years, FVC in Qinling region is in a good condition, with 73.11% vegetation coverage of medium, high and above; FVC will increase from 62.86% in 1986 to 70.01% in 2019, and vegetation activity will continue to increase; the mean coefficient of variation of FVC is 0.34, the standard deviation is 0.45, and its stability is highly autocorrelated with its spatial distribution; vegetation cover change in Qinling mountains is affected by climate change and human factors.

Analysis of impervious surface change in Ordos city based on multi-temporal remote sensing

ZHAO Chuanwu, WU Ziruo, ZHANG Yuhuan, GUO Wei

2022, 0(5):  56-61.  doi:10.13474/j.cnki.11-2246.2022.0141

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As an important assessment factor of urban development and ecological environment, impervious surface area (ISA) is of great significance in ensuring ecological health and sustainable urban development. In this paper, Ordos is taken as the study area and ISA information from 1990-2019 is extracted by fusing multi-temporal Landsat and nighttime lighting data (NTL), and the spatial and temporal evolution patterns are analyzed using the center of gravity analysis method, standard deviation ellipse theory (SDE) and landscape index theory (LI). The results show that:①From 1990 to 2019, the ISA of the Ordos city has experienced rapid expansion; the coverage of ISA in the northeast is higher than that in the southwest; the expansion pattern of ISA is:generally characterized by "outward expansion-inward encryption". ②The expansion rate in the northeast is slowing down, while the expansion rate in the southwest is increasing. ③ The directionality of ISA expansion is decreasing; the direction of ISA expansion is changing from "northeast-southwest" to "east-west". ④The number of patches increases, the fragmentation of edge patches increases, the connectivity between urban and suburban areas increases, and the city tends to expand to the surrounding suburbs. This study is a useful reference for further understanding the relationship between urban ecological health and sustainable urban development.

Terrain extraction method of Poyang Lake based on remote sensing image

ZHANG Gongquan, YUE Jianping, LIU Shengnan, WANG Hailong, YANG Zhixiang, ZHOU Hangyu

2022, 0(5):  62-66,73.  doi:10.13474/j.cnki.11-2246.2022.0142

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The inversion of lake bottom topography using remote sensing images has the advantages of simple operation and short processing period. Taking Poyang Lake as the research object, this paper proposes a method of lake bottom terrain inversion based on Kriging method. By analyzing the correlation between the spatial position and water level of eight water level stations around Poyang Lake, the change trend of lake boundary water level is obtained. The Kriging method is used to retrieve the water level of Lake boundary points, and the water level of boundary points is used as elevation points for lake bottom terrain inversion and the shape data verifies the reliability of the inversion method. The results show that the standard average error of cross validation is less than 0.2 m, and the average absolute error of terrain inversion is less than 1 m, which indicates that this method can be used for lake bottom terrain inversion with high accuracy.

Reconstruction of remote sensing image building contour based on end-to-end stacked hourglass network

ZHANG Xingyi, LI Jiatian, YANG Ruchun, LU Dajin, ZHANG Zelong, YANG Chao

2022, 0(5):  67-73.  doi:10.13474/j.cnki.11-2246.2022.0143

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Considering the problem that how to reconstruct building contour in an end-to-end trainable way, a method of building contour reconstruction based on end-to-end and multi-residual module stacked hourglass network is proposed. Firstly, the multi-residual module stacked hourglass network is used to extract features of buildings' corners and edges. Secondly, the corners detection module is used to match the relative positions of the corresponding corners to obtain candidate corners, and then the candidate corners are sampled by line sampling module to generate candidate contour lines. Finally, the line verification module used candidate contour lines and feature map obtained by stacked hourglass network verify whether each line segment is a building contour, so as to obtain the result of building contour reconstruction. Experimental results show that on SpaceNet building data set, this method can detect the corners and edges of buildings, and effectively reconstruct the building contour in an end-to-end trainable way.

Rural road crack segmentation method in complex scene

ZHANG Jinhe, QIN Yuluo, ZHANG Zaiyan, SONG Weidong, ZHU Hongbo

2022, 0(5):  74-78,88.  doi:10.13474/j.cnki.11-2246.2022.0144

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Aiming at the problems of small number of training samples, single scene and inaccurate extraction results in rural road crack identification,based on the measured road image data of Liaoning province for many years,this paper constructs a pavement crack datasets (PCDs) with multiple types and scenes,using ResNet50 network as encoder and SegNet as decoder,a pavement crack image recognition network Res-SegNet is constructed,by increasing the size of the convolution kernel to obtain more abundant crack information,the Focal Loss function is used to makes the model more focused on difficult samples.The block prediction method is used to improve the proportion of fractures in the image and make the image prediction more precise.The network model and prediction method are compared:The test set of PCDs is identified by Res-SegNet in different scenes, the average F value is 0.691,Res-SegNet combined with block prediction is used to identify the test set of PCDs,and the average F value is 0.753 in different scenarios.

A supervoxel-based active relearning framework for LiDAR point clouds classification

TAN Yuhui, LIU Xinyi, ZHANG Yongjun

2022, 0(5):  79-83,100.  doi:10.13474/j.cnki.11-2246.2022.0145

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To overcome the problem that the existing supervision methods require a large number of training samples and the high cost of manual labeling, a supervoxel-based active relearning method is proposed. Firstly, feature extraction is performed on the point cloud. Secondly, training samples are selected through the active learning method with supervoxel constraint and manually labeled. Finally, the relearning method is used for post-processing, and the classification results are continuously optimized by iterative calculation of category statistical features. The experimental results indicate that compared to using all training samples, the proposed method can achieve the same overall accuracy using less than 6% of all samples, which greatly reduces the cost of manual labeling. And the relearning algorithm also improves the classification accuracy.

Evaluation of mountain sponge city ecological construction based on landcover types

PAN Jianping, FU Zhanbao, CHENG Weihua, LU Shian, LI Xin, SUN Bowen, HUANG Guiping

2022, 0(5):  84-88.  doi:10.13474/j.cnki.11-2246.2022.0146

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The construction of sponge cities is an important measure to solve urban rain water management. However, the construction of mountain sponge cities is still in the development and exploration stage, and a comprehensive evaluation system has not been established. In view of the inadequate use of landcover type information and the lack of evaluation criteria in mountainous city construction, the combination of terrain factors, based on the types of urban surface cover and terrain factors, the paper establishes ecological evaluation indicators for mountain sponge cities. Firstly, obtain the two-temporal land type information of the study area. Then calculate the land type change detection results, and combine the elevation and slope to evaluate the regional sponge city construction. Finally, between the two time periods, the green area rate increases by 0.22%, the impervious surface rate increases by 0.46%, and the construction land developes to the middle terrain area. At the same time, the change status of the remaining land types is learned. The results show that the rate of green land in this area has increased, the protection of natural water bodies is better, the proportion of permeable surface is larger than that of impervious surface, and the development of ecological construction and construction land still conforms to the principle of mountain sponge city.

Coupling relationship between land subsidence and groundwater in Beijing-Tianjin-Hebei region based on GRACE data

ZHANG Yupeng, ZHANG Yonghong, LIU Qinghao

2022, 0(5):  89-94,125.  doi:10.13474/j.cnki.11-2246.2022.0147

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The excessive exploitation of groundwater has caused serious ground subsidence in Beijing, Tianjin and Hebei. In order to analyze the coupling relationship between groundwater and ground subsidence, firstly, the groundwater change sequence in Beijing-Tianjin-Hebei region from 2016 to 2019 is performed by using GRACE-FO data and GLDAS data; Then the time series of the subsidence change in the same period of the region is performed by using the technology of MCTSB-InSAR. In the experiment part, the differential change sequence and trend line of ground water and ground settlement are obtained respectively, and the influence of groundwater on ground settlement is analyzed by using inelastic storage coefficient. The results show that:①when the groundwater reserves increase or decrease rapidly, the ground subsidence rate decreases or increases. When the groundwater continues to rise, the ground subsidence is close to stop.②The more serious the settlement, the stronger the correlation between groundwater and ground subsidence.③The capacity of settlement caused by groundwater change increases with the increase of settlement level, and the change trend of the capacity with time is also different in different settlement grades.

Analysis of bridge deflection deformation based on ground three-dimensional laser scanning

ZHAO Lidu, XIANG Zhongfu, ZHOU Yin, MA Xiaping, ZHANG Shuangcheng, SI Mengyuan, CHEN Maolin, HU Chuan, PAN Jianping

2022, 0(5):  95-100.  doi:10.13474/j.cnki.11-2246.2022.0148

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Traditional methods of bridge deformation monitoring usually depend on deformation data of several independent points, which has the problems of low automation degree, low efficiency and limitations. In this article, an accurate method for bridge deflection is proposed. This method accurately registers the point cloud data of the bridge obtained by the ground 3D laser scanner. On the basis of obtaining reliable point cloud data, the bridge alignment is obtained by using the sliding window method, and the deflection of the bridge are obtained by using the difference analysis of two periods of data. Taking a continuous rigid frame bridge with a span of (40 m+65 m+40 m) as the experimental object, it is found that there are deflection deformations with a minimum value of 8 mm, a maximum value of 17.5 mm and an average value of 14.9 mm. Results prove that the method is simple and practical, with strict theory, high computational efficiency. It has important reference significance for the deep application of 3D laser scanning technology in the field of deformation monitoring.

RTK+IEZ pedestrian position method aided by magnetometer turn-detection HDE for harsh environment

ZHANG Chao, JIANG Jinguang, WU Jiaji, XIE Dongpeng, YAN Peihui

2022, 0(5):  101-105,149.  doi:10.13474/j.cnki.11-2246.2022.0149

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The accumulation of position and heading errors of traditional INS-EKF-ZUPT (IEZ) method will make the position accuracy deteriorate rapidly in harsh environment. Therefore, a magnetometer turn-detection heuristic drift elimination (MTHDE) algorithm which can be integrated with RTK into IEZ is proposed, and a RTK+IEZ+MTHDE pedestrian position method for environment with four orthogonal main directions is designed. The RTK+IEZ+MTHDE pedestrian position method is verified in an approximately 800 m rectangular experimental trajectory with open areas, tree-lined roads, semi-occluded buildings, and indoor environment. The results show that RTK and MTHDE algorithms reduce the position and heading errors of IEZ, in the experimental trajectory of 12 reference points, the average plane positioning error of RTK+IEZ+MTHDE method is 1.35 m, which is better than traditional RTK+IEZ method.

Study on the change factors of construction land in Taiyuan by integrating geographic detector and geographically weighted regression

ZHANG Rui, LI Chaokui, YAO Siyu, LI Weigui

2022, 0(5):  106-109,119.  doi:10.13474/j.cnki.11-2246.2022.0150

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Accurate identification of the change of construction land in the process of urbanization and the driving force behind it is of great significance to the subsequent sustainable development of cities. Based on remote sensing images from 2000 to 2020, this study studied the spatial distribution changes of construction land in Taiyuan city, and then combined the geographic detector model and the geographically weighted regression model to study the driving factors influencing the spatial distribution of construction land in the study area, and the following conclusions were reached:In addition to the policy factors, the existing urban construction land spatial distribution changes are also affected by elevation, traffic, GDP, population and other factors. The distribution of urban construction land change in Taiyuan is not only the result of the uniform, independent and direct effects of the four significant factors, such as GDP change, population change, altitude change and highway network density, but the product of the synergistic effects of the pairwise interaction of various factors with spatial heterogeneity. The results of this study are expected to provide a new way to study the driving forces of urban construction land. Key word:Taiyuan; geographic detector; geographically weighted regression; land use change; impact factors

A parallel framework for data-intensive geospatial analysis on large-scale vector polygons over hybrid CPUs and GPUs

XU Yunyun, ZHOU Chen, LI Manchun

2022, 0(5):  110-119.  doi:10.13474/j.cnki.11-2246.2022.0151

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In this study, we present a parallel framework for data-intensive geospatial analysis on large-scale vector polygons over hybrid CPUs and GPUs (PFGAP). We consider workload balance in terms of operator, data, granularity, parallel environment, and task scheduling, respectively. These modules constitute the PFGAP and the parallel implementation details are encapsulated. Through applying the PFGAP, the parallel version of a serial algorithm can be easily achieved with a proper degree of workload balance. The typical polygon triangulation, polygon rasterization, and projection transformation algorithms are employed as testing algorithms, and land-use datasets are used as testing datasets. Results show that the implemented parallel algorithms reduce significantly the serial execution time, achieving optimal speedup ratio of 40.03. In addition, the parallel strategies involved in each module are evaluated, showing better effectiveness with conventional ones.

Combining toponymy knowledge and location information for Chinese place names matching

JIANG Songyan, SONG Guomin, JIA Fenli, CHEN Lingyu, ZHANG Lantian

2022, 0(5):  120-125.  doi:10.13474/j.cnki.11-2246.2022.0152

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Aiming at the ambiguity in Chinese place names such as "same name for different locations" and "different names for same location", we propose a method for place names matching with combining toponymy knowledge and location information. Firstly, the semantic structure of place name is analyzed based on rule matching pattern of feature words. Afterwards, combining the location information, place names matching is achieving. Meanwhile, place name data is correlated by the entity information and administrative division to construct toponymy knowledge base. Taking POI data as instance, we implement place names matching with name similarity and location similarity, and the results are stored and represented in the form of knowledge graph.

HRNet-based extraction of building change information from high-resolution remote sensing images

CHEN Zhilang, FU Zhenhua, ZHU Ziyang, WANG Huihui, LIU Qinwen, YANG Yuling, XU Gengran

2022, 0(5):  126-132.  doi:10.13474/j.cnki.11-2246.2022.0153

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Building change extraction is one of the important research areas of remote sensing image information extraction, which is of great significance for land survey, natural resources monitoring and land law enforcement. The complex construction structure in Lingnan area of China contains a variety of building structure details, which reflect rich information on the high-resolution remote sensing images, and the factors of influence such as abundant data sources and imaging seasonal differences. It makes the automatic extraction of building change information very difficult. To address this problem, this paper proposes a semantic segmentation model based on HRNet, which achieves the retention of more detailed texture information by screening the feature layers that retain high resolution. On this basis, the automatic detection capability of building changes in high-resolution remote sensing images is improved by GraphCut binarization optimization.

High-precision automatic reconstruction of railway line with UAV oblique photography

WANG Guangshuai

2022, 0(5):  133-139,156.  doi:10.13474/j.cnki.11-2246.2022.0154

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Aiming at the problems of difficulty in surveying and mapping of existing railway line, low operation efficiency and insufficient measurement accuracy, this paper proposes a high-precision reconstruction algorithm for existing track lines based on the principle of unmanned aerial vehicle (UAV) multi-view geometry. Firstly, extract the straight line segment from the UAV images. Then, the image-based measurements are used to obtain candidate matching lines, and Powell optimization based on the distance are performed to obtain accurate rail line matching results. Finally, using the image rail line matching results as the observation value and the reprojection distance of the rail lines is used as a measure, the coordinate of rail straight line segments is optimized by the least square method. Experimental results show that the proposed method realizes automatic image rail line matching and high-precision adjustment solution. The image-based reprojection residual is better than 0.5 pixels, and the internal coincidence accuracy of railway gauge and rail height are 0.006 m and 0.005 m, respectively. The horizontal and vertical accuracy of the proposed method can reach about 2 cm, and the adjustment model has good convergence, which could meet the requirements of engineering application.

Study on the effects of point density on DEM accuracy of airborne LiDAR

WANG Daojie, CHEN Bei, SUN Jianhui

2022, 0(5):  140-144,169.  doi:10.13474/j.cnki.11-2246.2022.0155

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As an advanced remote sensing technology, airborne LiDAR is one of the important means to obtain high-precision digital elevation models (DEM) of vegetation coverage area. Different terrain slope conditions and point cloud density have an important impact on the accuracy of DEM products. Based on airborne LiDAR point data from a city in Liaoning province, this paper selects the point cloud data with different terrain slopes from 0° to 50° and adopts three different point cloud thinning methods:random, equidistant and curvature. The original point cloud is thinned and simplified according to the thinning multiple of five different gradients with the point cloud retention rate of 80%,60%,40%,20% and 10%,and the corresponding DEM is generated and its accuracy is evaluated. Based on this, the influence of terrain gradient, point cloud thinning method and thinning multiple on DEM accuracy is studied. The results show that there is a negative correlation between DEM accuracy and terrain slope, that is the RMSE increases with the increase of terrain slope.Compared with the other two methods,the RMSE of curvature based thinning method is smaller when the terrain slope is greater than 30° and has obvious advantages.When the point cloud retention rate is less than 40%, the RMSE of DEM will increase rapidly.This research has certain guidance and reference significance for large-scale DEM production using airborne LiDAR.

Achieving of USV group cooperation and control on hydrographic survey

WANG Lianhe

2022, 0(5):  145-149.  doi:10.13474/j.cnki.11-2246.2022.0156

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To resolve the issue of consistency when unmanned surface vessel(USV) group operate collaboratively in hydrographic survey,in this paper adopting the method of cooperative and control based on consistency theory, controlling multi-USV collaborative operation is studied, which has been applied in multi-USV cooperative survey.According to different survey tasks, a distributed consistency controller is designed to meet the requirements.The self-organized network survey system is modeled, model matrix and characteristic equation areconstructedfor the whole formation network. By analyzing the characteristic roots of the model matrix, the key information of the entire formation network is obtained, and time constraint is added. By solving the corresponding feasible solution, the consistent formation control algorithm is applied, combined with the key information of the formation network. Finally, the self-organized network formation achieves the consistency of the target and state quickly in a limited time.At the meantime, collision avoidance mechanism is added, so that multi-USV do not collide with each other at a safe distance. It has certain guidance and practical significance in the control of unmanned platform to operate collaboratively.

Performance analysis of BDS/GPS/GLONASS non difference non combination PPP in low latitude and high altitude area

ZHANG Dongsheng, ZHANG Yuying, LI Guozhu, ZHAO Zilong, YANG Suxin

2022, 0(5):  150-156.  doi:10.13474/j.cnki.11-2246.2022.0157

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Based on the brief description of the non difference non combination theoretical model and parameter estimation, combined with IGS/MGEX precision orbit and precision clock difference products, this paper analyzes the performance of BDS/GPS/GLONASS system non difference non combination PPP in Yunnan, which is located at low latitude and high altitude. Through experimental research and analysis,it is concluded that the number of visual satellites in the single system positioning mode in this area is BDS>GPS>GLONASS. In the combined mode, the number of visual satellites of BDS system and other systems is basically greater than that of GPS and GLONASS system. The number of visible satellites is GRC>GC>RC>GR, and the PDOP value is GR>RC>GC>GRC. The number of visible satellites in the combined mode is basically 2~3 times that of the single system, indicating that the contribution of BDS system is greater than that of the other two systems in low latitude and high altitude areas. Multi system combination can obtain better satellite geometry, which has significant advantages over single system. In terms of positioning accuracy, the positioning accuracy can basically reach mm cm level under seven combined modes.

Analysis of three-dimensional surface movement under the framework of ITRF2014 of HNGICS

GAO Yantao, ZHAO Hailiang, DING Laizhong, GUO Lingfei, ZHU Lin, SONG Huichuan, LI Chunyi

2022, 0(5):  157-161.  doi:10.13474/j.cnki.11-2246.2022.0158

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In view of the surface subsidence problem in Henan province, the continuous collection and operation system of Henan province geological information (HNGICS) is used for the first time to analyze the surface deformation in the entire province. In this paper, three-dimensional coordinates under the framework of ITRF2014 of HNGICS datum station with 10-years time baseline are compared to obtain the three-dimensional velocity field in Henan province, and the laws of surface deformation in Henan province are analyzed, which are related to the geological environment.The results show that there is 16 reference stations within 10 mm and 15 stations between 10 mm and 20 mm in Henan province. The overall trend is taken from west to east. The dominant direction of horizontal displacement in the south is 30.70°,and the average velocity is 0.87 mm/a. The prevailing direction of horizontal displacement in the north plain is 82.60°.The rate is 1.6 mm/a and there is noticeable relative movement on the surface of the province. Vertical direction, the average settlement rate in the eastern plain area is 11.0 mm/a, and that in the mountainous area is 1.4 mm/a. The settlement rate in the mountainous area is much lower than that in the plain area.

Geospatial data combined with multi-source data such as mobile phone signaling data to depict the travel characteristics of city residents

WANG Meihong, HOU Xiaoyu, SI Lianfa, HE Feng

2022, 0(5):  162-165.  doi:10.13474/j.cnki.11-2246.2022.0159

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The paper proposes ways to depict the travel characteristics of city residents combined with multi-source data such as mobile phone signaling and POI.Firstly,binds signaling data to geographical information blocks and identifies the basic job, housing and entertainment information of residents according to time characteristics and social attributes of geographical data. Then,mix POI people's livelihood interest, travel characteristics development keywords such as multiple source data, uses weekday commuting analysis model and holiday travel characteristics extraction model to identify the user's commuting distance, commuting, daily commuting frequency, weekly working hours, holiday travel scene, travel frequency, residence time, and form entertainment information travel characteristics label set. Taking Chengdu as an example, collects a month of mobile phone signaling data and POI data in the same period to verify the feasibility of the method. The results reflect the actual urban population size and spatial distribution characteristics of urban population map of big data products and provide support for government departments, commercial enterprise users to carry out relevant analysis business.

Practice of transformation and upgrading for surveying and mapping major under emerging engineering education

GAO Jingxiang, CHEN Guoliang, WANG Qianxin, LI Zengke, ZHANG Shubi, WANG Yunjia, ZHANG Qiuzhao, LIU Zhiping

2022, 0(5):  166-169.  doi:10.13474/j.cnki.11-2246.2022.0160

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The Ministry of Education has proposed that one of the purposes of emerging engineering education in colleges and universities is to cultivate innovative talents with engineering practice ability.The development trend of surveying and mapping science and technology has gradually changed from analog surveying, digital surveying and information surveying to intelligent surveying. The development of surveying and mapping instruments and methods has presented new challenges to surveying and mapping majors and has higher requirements for the comprehensive ability required by talent cultivation.Taking the transformation and upgrading of the mine surveying major of China University of Mining and Technology as an example, the project team has deeply discussed the reform ideas of the development of surveying and mapping engineering major with industrial characteristics and the cultivation of innovative talents under emerging engineering education situation, and promoted the transformation and upgrading of the surveying and mapping from the traditional major to the emerging engineering education major of combining "space-sky-earth-mine".

Reconstruction method of complex steel structure model based on LiDAR point cloud

XU Fubin, QU Xiangyi, WANG Jian, LIU Xiuhan

2022, 0(5):  170-173.  doi:10.13474/j.cnki.11-2246.2022.0161

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In order to solve the problems of traditional single-point measurement techniques based on total stations such as difficulty in obtaining overall information of steel structures, slow measurement speed and low model reconstruction accuracy, this paper applies the three-dimensional laser scanning technology to the field of steel structure model reconstruction, and proposes a complex steel structure model reconstruction method based on LiDAR point cloud. Firstly, the high-precision registration of multi-station point cloud is realized based on the target sphere and structural plane information, and the noise is removed by radius filtering algorithm to obtain the complete laser point cloud data. Then,the single model is segmented to realize the model reconstruction of each component of steel structure. Finally, the accuracy of the reconstructed three-dimensional model is evaluated according to the field measured data. The experimental results show that the accuracy of the model obtained by this method is high, and the difference between the model and the actual size is within 1 cm, which provides an effective solution for the three-dimensional model reconstruction of complex steel structure.