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Expansion law analysis of Taiyuan built-up area in recent 50 years based on long time series of remote sensing data ZHAO Hengyang, LIU Xin, ZHAO Shangmin Bulletin of Surveying and Mapping    2021, 0 (9): 83-88.   DOI: 10.13474/j.cnki.11-2246.2021.0279 Abstract （782）            Knowledge map    Save Based on remote sensing images of Taiyuan from 1973 to 2020, artificial visual interpretation and Google historical image correction are used to extract built-up areas. The compactness, expansion intensity, expansion speed and gravity center transfer model are introduced to analyze the spatiotemporal evolution characteristics of built-up areas in Taiyuan in the past 50 years. The main driving factors of expansion of Taiyuan built-up area are analyzed. The results show that:① From 1973 to 2020, the built-up area of Taiyuan has expanded by 15.12 times, with an average annual increase of 7.85 km 2/a. The compactness of the built-up area is generally low and the expansion is obvious in the north-south direction. The center of gravity migrates more than 3500 m along the southwest direction of about 30°. ② The main factors causing the expansion of Taiyuan built-up areas are economy and population expansion, among which GNP and per capita GDP play a key role. Reference | Related Articles | Metrics

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Using FME and VBA to extract the elevation data of airport grid LI Chengpeng, YANG Yuanxin, ZHANG Yunming Bulletin of Surveying and Mapping    2021, 0 (8): 129-134.   DOI: 10.13474/j.cnki.11-2246.2021.0256 Abstract （691）            Knowledge map    Save The ground of the point cloud classification after get point cloud data currently in LAS cannot completely applied to design software for design calculation. Through the screening of the proposed technical scheme, the method of using the data processing function of FME Workbench combined with VBA programming to provide the plane data of external grid is proposed. In the FME Workbench, the ground point cloud data is used to construct TIN, the grid elevation data is extracted from TIN by point-by-point interpolation method, the contour line is generated, the corresponding graphic processing and the output of results are achieved, and the effectiveness of the method is demonstrated by the actual calculation examples. Reference | Related Articles | Metrics

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New surveying and mapping for the urban digital transformation of Shanghai GU Jianxiang, DONG Zhen, GUO Wang Bulletin of Surveying and Mapping    2021, 0 (7): 131-134,139.   DOI: 10.13474/j.cnki.11-2246.2021.0223 Abstract （671）            Knowledge map    Save Urban digital transformation, "scientific, refined, and intelligent" urban governance, the implementation of "new infrastructure" and the development of digital economy all urgently need spatial geographic data to advance to "full domain, holographic, full space, multidimensional, and high-frequency" and realize the digital twin of physical space. This article combines the new needs of geographic information in the urban digital transformation of Shanghai, proposes a new surveying and mapping system with intelligent pan-info surveying and mapping which based on geographical entities as the core from the aspects of multiplatform collection technology, holographic data content, 2D and 3D integrated form of results, update method and on-demand assembly of services, and forms a solution to new geographic information services for urban digital transformation. Reference | Related Articles | Metrics

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DMSP-OLS and NPP-VIIRS night light image correction in China GUAN Jingyun, LI Dong, WANG Yafei, WANG Xinyun Bulletin of Surveying and Mapping    2021, 0 (9): 1-8.   DOI: 10.13474/j.cnki.11-2246.2021.0264 Abstract （660）            Knowledge map    Save Based on the improvement of the traditional invariant target area correction method, this study selects the four-phase radiometric calibration reference image to perform saturation correction and time series continuity correction for DMSP-OLS images.The threshold method was used to remove the background noise and abnormal values of the NPP-VIIRS image, and the dynamic range of the light radiation value is compressed by the logarithmic transformation so that the brightness distribution is closer to the DMSP-OLS data.Then the NPP-VIIRS image was uniformly corrected through the BiDoseResp function model, and the long-time sequence of night light images from 1992 to 2019 was obtained.Finally, the accuracy of the calibration results is verified in terms of qualitative, quantitative, and the correlation between the corrected image and the socio-economic parameters.The results show that the improved correction method improves the severe saturation of DMSP-OLS images, and makes it obtain the longitudinal comparability of long-term series.The BiDoseResp function model can fit the regression between DMSP-OLS and logarithmic transformation NPP-VIIRS well.The corrected long-term sequence of light image data is highly consistent with the socio-economic parameters. The correction results are of great value to promote the wide application of long-time sequence night light images and to deepen the research of long-term sequence scientific problems. Reference | Related Articles | Metrics

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The exploration and practice of geographic information science specialty construction in Central South University DENG Min, CHEN Jie, LIU Huimin Bulletin of Surveying and Mapping    2021, 0 (7): 156-159.   DOI: 10.13474/j.cnki.11-2246.2021.0228 Abstract （625）            Knowledge map    Save The "Double Ten Thousand Plan" of the Ministry of Education emphasizes the construction of a first-class profession that faces the future, adapts to needs, leads development, is advanced in concept, and has strong guarantees. This article explains how the geographic information science major of Central South University combines school positioning and professional characteristics, and teaches students in accordance with their aptitude, and has a unique professional construction road. It explores and implements a series of measures for the geographic information science major of Central South University. The professional development has made great progress. Reference | Related Articles | Metrics

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Registration and seamless fusion of point cloud from LiDAR and oblique photography RUAN Minghao, LU Yonghua, LIU Yuxian, TANG Shengjun, WANG Weixi, ZHANG Yuqi, LI You Bulletin of Surveying and Mapping    2022, 0 (4): 6-10.   DOI: 10.13474/j.cnki.11-2246.2022.0101 Abstract （612）            Knowledge map    Save The traditional and widely used urban space modeling methods such as laser point cloud and oblique photography have their own advantages and disadvantages. How to effectively integrate data from different sources and use them in the construction of city 3D models is the current difficulty in city modeling. Therefore, this paper proposes a precise registration and seamless fusion method for laser and oblique point clouds. This method can overcome the inconsistency of scale and accuracy of point cloud data from different sources, accurately calculate the spatial transformation relationship of data from different sources, and on this basis, data redundancy is eliminated, and the seamless integration of multi-source point cloud data is completed. Finally, this paper uses the data obtained in three sets of actual scenes to verify the effectiveness and accuracy of the elimination method in this paper. The experimental results show that the fusion data obtained by this method has better completeness and data accuracy than the single platform data. Reference | Related Articles | Metrics

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Accuracy evaluation of GPS, BDS and GPS+BDS precise point positioning LI Jiangang, LI Honghui, CHAI Xiangjun, WANG Tianyu Bulletin of Surveying and Mapping    2021, 0 (9): 124-129.   DOI: 10.13474/j.cnki.11-2246.2021.0288 Abstract （582）            Knowledge map    Save In view of the completion of BeiDou satellite network, it is necessary to evaluate and analyze the system performance of BDS. The 31 day observation data collected by multi GNSS experience network is selected to compare and analyze the precision of static and dynamic precise point positioning under different conditions of GPS, BDS and GPS+BDS. The experimental results show that the accuracy of GPS and BDS single system static PPP in N, E, U direction is better than 4, 4, 7 cm, respectively; GPS+BDS combined system static PPP accuracy in N, E, U direction is better than 3, 3, 6 cm; GPS single system dynamic PPP accuracy in N, E, U direction is better than 5, 5, 10 cm; BDS single system dynamic PPP accuracy in N, E, U direction is better than 5, 6, 12 cm; GPS+BDS integrated system dynamic PPP accuracy is better than 4, 4, 8 cm in N, E, U direction. So the integrated system can improve the stability and accuracy of positioning compared with single system, and the advantages of the combined system are more obvious in the case of dynamic PPP. Reference | Related Articles | Metrics

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Image overlap calculation model and application in oblique photogrammetry ZHAO Zhixing, LU Xiaohong, TIAN Xin, LIU Zhiqi Bulletin of Surveying and Mapping    2021, 0 (9): 89-92.   DOI: 10.13474/j.cnki.11-2246.2021.0280 Abstract （570）            Knowledge map    Save According to the position structure of the multi-lens cameras in the tilting aerial camera, the relationship between the corresponding coverage area of the oblique image, course, lateral overlap degree and flight speed, exposure interval time, route interval and other parameters is analyzed. On this basis, a formula for calculating the overlap degree of images taken by cameras at any number, any angle and any position is derived. The result proves that this method improves the accuracy of setting parameters of tilt photography and provides a necessary basis for the quality assurance of the later process. Reference | Related Articles | Metrics

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LiDAR point cloud ground filtering algorithm in dense and low vegetation area YAN Yueguan, CHEN Zhongzhang, SUN Yang, LI Zezheng, YAO Chengzhi Bulletin of Surveying and Mapping    2021, 0 (7): 1-5.   DOI: 10.13474/j.cnki.11-2246.2021.0199 Abstract （557）            Knowledge map    Save Aiming at the characteristics of LiDAR point cloud in mining areas with complex terrain and dense low vegetation, this paper proposes a ground filtering algorithm based on slope information combined with plane fitting. This method uses the second-level grid method to select ground seed points by hierarchical extraction, and uses the ground seed points in each first-level grid to construct a ground model by plane fitting through the least squares fitting method. Finally, ground point and non-ground point can be distinguished. Through comparative experiments with the traditional slope filter and cloth simulation filter, it is concluded that this method can effectively filter out dense and low shrubs and can better retain the larger slope terrain. Reference | Related Articles | Metrics

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IMU calibration using Vicon system WANG Zhigang, GUO Hang, AO Longhui Bulletin of Surveying and Mapping    2021, 0 (7): 121-125.   DOI: 10.13474/j.cnki.11-2246.2021.0221 Abstract （539）            Knowledge map    Save Aiming at the problem that the traditional IMU calibration method is complicated to operate and relies too much on the turntable, an IMU calibration method for Vicon system is proposed. Firstly, the pre-integration technique is used to fuse the IMU data with the Vicon data to obtain the IMU residual. Then, the state quantity between the adjacent frames of Vicon is subtracted to obtain the Vicon residual. Finally, the IMU residual and the Vicon residual are put into the same state vector, and the marginal prior information is introduced to establish a nonlinear optimization function, and the zero offset estimation parameters of the gyroscope and accelerometer are obtained by solving.In the meantime, the EuRoc data set test experiment and indoor positioning comparison experiment are designed. The experimental results show that the calibration result of this method for IMU has higher accuracy whichis much better than that of the traditional method. Reference | Related Articles | Metrics

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Generative adversarial network super-resolution reconstruction for single remote sensing image HAN Zhisheng, SUN Pichuan, TANG Chao Bulletin of Surveying and Mapping    2021, 0 (8): 106-110.   DOI: 10.13474/j.cnki.11-2246.2021.0251 Abstract （529）            Knowledge map    Save The process of using low resolution (LR) images to predict the corresponding high resolution (HR) images is called image super-resolutions, which aims to get a clear image. With the vigorous development of artificial intelligence, image super-resolution reconstruction has more and more applications in many fields such as medical treatment and remote sensing. This article learns to use the deep learning model of generative adversarial networks (GAN) to perform single-image super-reconstruction. Compared with traditional methods, this model proposes a new perceptual loss function, including an adversarial loss and a content loss. The adversarial loss distinguishes the generated image from the actual high-resolution image by training the discriminator network structure, while content loss uses the pre-trained VGG19 network model to calculate the perceived similarity of image features, rather than the similarity in pixel space. The experiment proves that the introduction of generative adversarial network into single-image super-resolution, MOS score is higher than traditional methods. This article will focus on the principles, effects, and applications of SR and GAN. Reference | Related Articles | Metrics

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Simplification of tilt photogrammetry 3D model and service release ZHANG Huixia, LI Hao, LI Jinhong, ZHAO Fei Bulletin of Surveying and Mapping    2021, 0 (9): 79-82.   DOI: 10.13474/j.cnki.11-2246.2021.0278 Abstract （505）            Knowledge map    Save In order to provide services for relevant departments in population management and realize smart community. In this paper, we study the simplification and attribute query of three dimensional model of inclined photography in residential area. Through the simplification of three dimensional model data by layers and households, we establish a database, and release the simplification model and real 3D model on the network, so as to query the information of each house separately, and realize the beautification of pop-up window and the display of photo information through programming technology. Finally, a practical example shows that the method is feasible. The purpose of this study is to provide support for relevant departments to carry out population management services and realize smart community. Reference | Related Articles | Metrics

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Block filtering method for LiDAR point cloud fusion image MAO Donghai, LI Shoujun, WANG Feng, DAI Huayi, YANG Fanlin Bulletin of Surveying and Mapping    2021, 0 (10): 67-72,131.   DOI: 10.13474/j.cnki.11-2246.2021.307 Abstract （503）            Knowledge map    Save Aiming at the problem that the existing LiDAR ground point filtering algorithm is not adaptable to complex terrain and objects, a block filtering method combining point cloud and ground image is proposed in this paper. Firstly, the ground image is matched with the point cloud to make it obtain more spectral texture information from the image. Secondly, the ground feature spectrum, forest land relative density, point cloud elevation characteristics, DSM model and its slope are fully analyzed, and the original point cloud is cut into several independent blocks based on decision-making level fusion. Finally, according to the different multivariate detail characteristics of each region, the IPTD filtering algorithm is improved and the parameters are optimized by the search method to obtain the optimal and robust results. Using the filtered total ground points, the DEM model obtained by interpolation algorithm and related experiments verify the superiority of the proposed algorithm. Reference | Related Articles | Metrics

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Early identifying and monitoring landslides in Guizhou province with InSAR and optical remote sensing WU Lüchuan, WANG Jianhui, FU Yan Bulletin of Surveying and Mapping    2021, 0 (7): 98-102.   DOI: 10.13474/j.cnki.11-2246.2021.0216 Abstract （501）            Knowledge map    Save The topography and landforms of Guizhou province in China are complicated, and the climatic conditions of heavy precipitation make landslide disasters in Guizhou province occur frequently. To avoid damage bringing to people's lives and economic property caused by disasters, a reliable early landslide identification method and landslide monitoring method are urgently needed. Traditional landslide identification and monitoring methods have limitations. InSAR technology has unique advantages in large-scale landslide identification and monitoring, but landslide identification results based on a single deformation value are one-sided. Therefore, this paper uses Sentinel-1A Radar satellite image data and uses InSAR technology and optical remote sensing technology togather to carry out large-scale surface deformation monitoring and identification of dangerous deformation areas in Liupanshui city, Tongren city, Guiyang city and other regions in Guizhou province. The potential landslide identification methods based on the time series normalized difference vegetation index and landslide development environment elements are combined to investigate hidden landslide hazards in the study area. In this paper, time series InSAR technology is used to monitor key landslides in Yujiaying, to grasp the movement status of the landslide in time. The method of landslide identification and monitoring in this paper is of great significance for disaster prevention and management in Guizhou province. Reference | Related Articles | Metrics

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An optimized Faster R-CNN small target detection method CHENG Rui, GAO Jian, XING Qiang, SUN Zhongchang Bulletin of Surveying and Mapping    2021, 0 (9): 21-27.   DOI: 10.13474/j.cnki.11-2246.2021.0267 Abstract （496）            Knowledge map    Save Image object detection is a popular direction in computer vision and digital image processing. Its main task is to find out the object of interest in the image and determine the location and category of the object. The current mainstream object detection algorithms are mainly based on deep learning models, and it has become a trend to solve many disciplinary problems. This article uses a method based on the combination of the regional convolutional neural network (Faster R-CNN) deep learning algorithm and related image processing algorithms,using ResNet50 and ResNet101 as the backbone network and using feature pyramid networks to monitor the changes of vehicles in Wuhan during the new crown epidemic to analyze the intensity of internal activities in Wuhan during the epidemic. The results show that the accuracy rate of the image detection method in this paper is 0.96, the recall rate is 0.915, and the average accuracy is 0.853 8.The vehicle number changes before the epidemic (November 17, 2019) and during the epidemic (February 22, 2020) is as follows:Wuhan Convergence Center (263 and 32 vehicles), Wangjiazui Overpass (89 and 44 vehicles), Xinxing Industrial Park (554 and 347 vehicles), Jingkai Future City (188 and 57 vehicles). The epidemic has led to a decrease in population travel and vehicle activities in Wuhan. Reference | Related Articles | Metrics

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ORB-SLAM method based on local adaptive threshold extraction feature points LI Guojun, XU Yanhai, DUAN Jiewen, HAN Shilei Bulletin of Surveying and Mapping    2021, 0 (9): 32-36,48.   DOI: 10.13474/j.cnki.11-2246.2021.0269 Abstract （485）            Knowledge map    Save Localization and mapping of intelligent driving vehicles is one of the key technologies of intelligent driving vehicles. Aiming at the problem of feature points extracted as fixed threshold in ORB-SLAM a local adaptive threshold method is proposed to extract feature points.Firstly, the calculation method of local adaptive threshold is described, and the adaptive threshold is set by image contrast.Secondly, Gaussian image pyramid is constructed on the basis of FAST algorithm and gray-scale centroid method is adopted to solve the scale invariant and rotation problem of feature points. The image grid area is divided in each layer of image pyramid and the contrast of each layer of image grid area is calculated to set the local threshold of each grid area.Finally, feature points are extracted in each image grid area and stored in quadtree structure.The test results show that the number of feature points extracted by the proposed algorithm is 61.9% more than that extracted by the original algorithm in cloudy days, and 23.3% more than that extracted by the original algorithm in sunny days.In cloudy and well-lit scenes, the fluctuation of the number of feature points extracted by this algorithm is less than that of the original algorithm. Reference | Related Articles | Metrics

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An easily FLAC3D modeling method based on geological information interpolation LI Peixian, CAO Yuxi, YANG Zhonghui, HAO Dengcheng Bulletin of Surveying and Mapping    2021, 0 (7): 6-11.   DOI: 10.13474/j.cnki.11-2246.2021.0200 Abstract （479）            Knowledge map    Save To obtain an easily method of FLAC3D modelling and reduce the difficult of using of FLAC3D, a program is developed using python. This program using the stratigraphic information to generate the discrete grid points based on Kriging interpolation first. And then the program can generate the FLAC3D grid format file automatically. The generated file can be imported into the FLAC3D software and a 3D model can be obtained directly and easily. It is faster and easier than using the inner modeling script. The program provides three basic elements model of the FLAC3D. The method can generate accurate 3D model using the Kriging interpolation. Three applications and some results of coal mines are given in the paper. Those applications show that it can generate accurate 3D model for complex topography. The research results provide a tool for building 3D models in complex geo-conditions simulation. Reference | Related Articles | Metrics

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Construction and application of city-level real 3D city: a case study of Linyi real 3D city CAI Zhenfeng, PENG Bin, JI Xia, JI Peng Bulletin of Surveying and Mapping    2021, 0 (11): 115-119,144.   DOI: 10.13474/j.cnki.11-2246.2021.350 Abstract （479）            Knowledge map    Save Real 3D cities have become 3D space supporting infrastructure and an important part of the construction of new infrastructure. The construction of real 3D cities is the basis for the comprehensive construction of real 3D China. This paper combines the construction of real 3D Linyi, and proposes the deep fusion technology of laser point cloud and oblique photography multi-source data with low overlap to quickly construct the technical process and system of city-level real 3D city. The data results have been deeply applied in large-scale topographic map surveying and mapping, the construction of the spatio-temporal information cloud platform and the management of 3D real estate registration, which is of practical significance for promoting the construction and application of city-level real 3D cities. Reference | Related Articles | Metrics

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Aerial LiDAR building point-cloud progressive extraction algorithm GAO Zhimei, WANG Jingxue, SHEN Zhaoyu Bulletin of Surveying and Mapping    2021, 0 (8): 7-13,36.   DOI: 10.13474/j.cnki.11-2246.2021.0232 Abstract （460）            Knowledge map    Save Aiming at the problem that is easily affected by adjacent vegetation, a building point-cloud progressive extraction algorithm is proposed in this paper for airborne LiDAR. Firstly, the ground point-clouds and the non-ground point-clouds are distinguished by using the cloth simulation filter. Next, the initial building point-clouds are extracted by using Otsu to get threshold to segment the non-ground point-clouds on the basis. Then, DBSCAN is used to eliminate outlier noise points on the initial building point-clouds through the connectivity of the point-cloud. Finally, the edge of the building is obtained through the Alpha Shape algorithm. The experimental selectes three sets of LiDAR point-cloud dates of different type of urban building provided by the ISPRS official website. The result shows that the algorithm of this paper can achieve the extraction of airborne LiDAR building point-cloud better. Reference | Related Articles | Metrics

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The key technology of large-scale channel reality 3D modeling WEN Guanghua, OU Yanghui, CHEN Guang Bulletin of Surveying and Mapping    2021, 0 (8): 115-118,143.   DOI: 10.13474/j.cnki.11-2246.2021.0253 Abstract （453）            Knowledge map    Save The traditional channel surveying and mapping information management and fusion technology is insufficient, and it is difficult to fully reflect the impact of the natural geographical environment, facilities and buildings on the water safety. Aiming at the problem of damage and missing of the reality 3D model of waterway, this paper introduces a multi-scale level set image segmentation method, that automatically initialized with the buffer image of hole, so as to obtain the accurate channel water area range by fast iterative segmentation, and further restrict the reality 3D model reconstruction and model singleization. This method is verified in the construction task of reality 3D channel map of Wangjiatan demonstration section of Yangtze River in Changshou District, Chongqing. Compared with the traditional model repairing and singleization method, the experimental results show that the technical method proposed in this paper is effective, which significantly improves the optimization efficiency of reality 3D model of waterway, and supports the safety management of waterway operation. Reference | Related Articles | Metrics