Table of Content

25 March 2023, Volume 0 Issue 3

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The hexagonal grid gravity field in future Earth system construction

LI Xinxing, FAN Haopeng, HUANG Yan, WANG Aoming, ZHANG Zhanpeng

2023, 0(3):  1-4.  doi:10.13474/j.cnki.11-2246.2023.0062

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In order to enhance the ability of geodesy to serve human social activities, building an Earth system including the earth's gravity field and maximizing the benefits of Earth system simulation and prediction will greatly promote the development of Earth system science and enhance the service capabilities of the discipline. The earth hexagonal grid system is widely used in the earth system, and it has advantages in the realization of earth gravity field modeling, data processing, multi-source data fusion, etc. This paper summarizes the limitations of traditional geographic grids and the advantages and potential of spherical hexagonal grids in the applications of the earth's gravity field. The study of the earth's gravity field under the hexagonal grid system will play an important role in improving the efficiency and accuracy of the earth's gravity field solution and in the unification of multiple earth system models.

An advanced denoising method for full-waveform LiDAR

SHI Zhiyuan, XU Weiming, MENG Hao

2023, 0(3):  5-9.  doi:10.13474/j.cnki.11-2246.2023.0063

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In the process of transmitting to receiving a full-waveform LiDAR signal, noise is generated due to the influence of the propagation medium, the scanning distance, the nature of the object and other factors.Aiming at the problem,this paper has put forward a modified denoising method based on empirical mode decomposition (EMD), permutation entropy (PE) and wavelet threshold method (WTM). Firstly, the initial echo signal is decomposed into several intrinsic mode functions (IMF) and then the PE value corresponding to each IMF is computed. Secondly, the PE value is utilized to form the wavelet threshold value, and new threshold function is constructed. Finally, after being denoised by corresponding WTM, all the IMFs are added and the denoised signal is obtained. Features of EMD, PE and WTM are took advantage of, which enables the new method to deal with noised echo signal adaptively. By making data simulation and measured data experiment, the new method is compared with other methods. Normalized indexes and comprehensive index based on signal-noise ratio, waveform relevance, root mean squared error and smoothness indicate that, the new method increase the normalized signal-noise ratio index by 10% to 20%, while the other indexes are advanced by 5% to 40%. It can be concluded that the new method put forward in this article has better effect and is able to deal with echo signal with different levels of noise during use of full-waveform LiDAR.

A dynamic commodity visual recognition method based on domain adaptation

LEI Yangyang, LI Li, SUN Fei, YAO Jian

2023, 0(3):  10-15.  doi:10.13474/j.cnki.11-2246.2023.0064

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Due to large deformation, occlusion, motion blur, similarity in appearance between items, and unknown distribution deviation in real scenes, item dynamic visual recognition still has huge challenges in practical applications. To this end, this paper proposes a dynamic commodity visual recognition method for smart retail. First, the bounding rectangle of the commodity is detected in real time through the target detection network, and then the category of the commodity is identified on this basis and recommendations are given to assist in the completion of consumer settlement. At the same time, in view of the cross-domain difference between the product picking video, the product library image, and the training image, this paper introduces a neighborhood style adaptive model (IBN) and a convolutional attention module (CBAM) to improve the domain adaptability of the model. In order to verify the effectiveness of this method, this paper constructs a real scene dataset Commodity247. The data is collected by the top-view camera of the smart container, including 247 common retail commodities and 37 050 pictures with annotated boxes and commodity categories. The experimental results show that on the Commodity247 dataset, the accuracy rate of product recognition(mAP) can reach 96.84%, the accuracy rate of the first recommendation(Rank1) can reach 98.41%, and the accuracy rate of the most difficult sample retrieval(mINP) can reach 85.24%, which is better than the one based on ResNet. For the basic model, mAP increases by 2.91%, Rank1 increases by 0.60%, and mINP increases by 10.86%, effectively reducing the influence of multi-angle, multi-light, and multi-background.

Hierarchical line matching of close range images

CHENG Fei, ZHANG Ziwen, CONG Risheng, JIN Zelin

2023, 0(3):  16-21.  doi:10.13474/j.cnki.11-2246.2023.0065

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In view of the geometric local constraints in line matching of close range images, there are some problems, such as missing selection and weak matching of descriptors under certain scene transformation. In this paper, a line hierarchical matching scheme for close range image is proposed. In this scheme, the kernel equation and perspective transformation matrix are obtained with reliable homonymous points, the target line is screened twice, and whether there is a reliable camera projection matrix in close range image is selected as the check method. If there is a camera projection matrix, the corresponding re projection error is calculated, Otherwise, the cosine similarity between the optimized MSLD descriptor vectors is calculated, and their reasonable thresholds are set as the final threshold to accept the line with the same name. The algorithm is analyzed and verified by using the network public data set. The experimental results prove the feasibility of this scheme, and can obtain accurate and stable line matching results of the same name. At the same time, it has good adaptability to a variety of transformed images.

An intelligent seamline extraction algorithm of DSM considering topographic changes in overlapping areas

GAO Yaping, WANG Yan, LIU Chunju, WANG Qi, WU Xiaxian

2023, 0(3):  22-26.  doi:10.13474/j.cnki.11-2246.2023.0066

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For the digital surface model data obtained by image dense matching, an intelligent seamline extraction algorithm considering the topographic changes in the overlapping area is proposed. This method uses the elevation deviation of the DSM data overlapping area to construct the difference images. It is fusion processing between difference images and the difference images after denoising, stretching and reverse calculation. For the fusion data, the optimal path search method based on the minimum spanning tree is used to extract the optimal seamline. The experimental results show that our seamline extracted can avoid the protruding ground objects effectively with large elevation differences and ensure the integrity of the ground objects. This method can solve the problem of automatic seamline selection in the process of mosaicking DSM data. The method effectively reduces the errors brought by the traditional mosaic method, and has high reliability and stability.

AprilTag image identification application to high distance transfer measurement method

CAO Zeqiang, SUN Yinghui, HONG Qiong, CHEN Wenyu, ZHOU Li

2023, 0(3):  27-32.  doi:10.13474/j.cnki.11-2246.2023.0067

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To facilitate computer vision and the application of intelligent robotics in traditional high difference measurements, a high differential transmission measurement method for non-contact application AprilTAG image recognition technology is proposed. As the Robomaster EP robot, the AprilTag label is placed in a known point and the standby point, and the robot camera identifies the AprilTag label on both sides and performs relative position. The three-dimensional sitting is followed, and then the high difference of the rotation center of the robot camera is calculated to be calculated to obtain a high difference from the known point relative to the known point. Through multi-group experiments, the effect of the pitch angle α of the robot camera is studied, and the change of the change of the torch β on the measurement accuracy of the high difference transmission. The experimental results show that when the tension of the robot camera is pitch angle α∈(-2.9°,3.9°], or when the head is angle β∈[-5.5°,1°], AprilTag image recognition is E<0.4, the recognition effect is better, and the two-point high difference error p_x is less than 5 mm, and the accuracy of the high difference transmission measurement can reach millimeters. The above experimental results show that the use of computer vision and intelligent robots have certain feasibility, providing a certain theoretical basis and technical exploration for the R & D industry to develop new intelligent measurement robots in the future surveying industry.

Forecasting the surface deformation of unstable slopes based on InSAR and GRU neural network

PAN Jianping, CAI Zhuoyan, ZHAO Ruiqi, FU Zhanbao, YUAN Yuxin

2023, 0(3):  33-38.  doi:10.13474/j.cnki.11-2246.2023.0068

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The prediction of surface deformation of unstable slope is crucial to landslide disaster prevention and early warning. The existing monitoring methods have small coverage and high cost. The relevant prediction methods are limited to single point prediction and have high requirements for the amount of historical data. To solve the above problems, this paper uses Small Base line Subset InSAR (SBAS-InSAR) technology to monitor the surface deformation of unstable slope, and designs a method for predicting the surface deformation of unstable slope based on the inversion results of InSAR and Gated Recurrent Unit (GRU) neural network. Firstly, the SBAS-InSAR technology is used to monitor the surface deformation in the study area, then the obtained time series deformation inversion results are used to establish the GRU model to study the deformation law, and finally carry out the surface deformation prediction of unstable slope.The experimental results show that the mean absolute error of this method for predicting the surface deformation of unstable slope is 0.678 mm,and the mean absolute error percentage is 2.7%.Compared with the traditional support vector regression (SVR) model,the prediction effect is improved by more than 30%, and the engineering application potential is great.

Analysis of data quality and multi-frequency positioning performance of BDS-3 in polar region

HU Rongming, XU Yu, JIANG Youyi, DU Yanjun, CHONG Yajie

2023, 0(3):  39-43,66.  doi:10.13474/j.cnki.11-2246.2023.0069

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In order to analyze the data quality and positioning performance of BDS-3 in the polar region, this paper evaluates the data quality based on the observation data of four stations near the north and south polar regions of MGEX during 7 consecutive days, and analyzes the positioning performance of different PPP combinations about dual-frequency and tri-frequency. The results show that the average number of visible satellites at the region of BDS-3 is about 10, the value of PDOP is 1.7, the data completeness is about 96.2% and 90.1% at the south and north polar regions, respectively. The value of SNR is a little difference between north and south region, both around 45 db-Hz, and the MP RMS is between 27~35 cm. In the polar region, the positioning accuracy of the BDS-3 PPP's dual-frequency and tri-frequency can reach 1~3 cm after convergence, and the positioning accuracy of the tri-frequency PPP is improved to a better extent compared with that of the dual-frequency PPP. The improvement accuracy of the IF combination in the direction of U is the largest, which is about 21.8%, and the average accuracy increase of UC combination is about 8.3%. The convergence time of dual-frequency and tri-frequency IF combination is 15.4 and 18.3 min respectively, which is better than 28.0 and 28.2 min of UC.

GNSS-PWV calculation method based on the GPT-3 model

GAO Ying, XU Siyi, LI Li, LU Houxian, HE Qimin, WANG Xiaoming

2023, 0(3):  44-48,103.  doi:10.13474/j.cnki.11-2246.2023.0070

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To solve the problem that precipitable water vapor (PWV) can't be calculated in real time without the measured meteorological parameters at some GNSS stations,taking the Yangtze River Delta region as an example, a new method to obtain high-precision PWV by combining GPT3 model with GNSS-ZTD is proposed in this paper. The results show that the meteorological parameters and some tropospheric delay parameters of GPT3 model have good stability and accuracies in the Yangtze River Delta region. The RMS of PWV obtained by integrating the parameters (ZHD and T_m) of GPT3 model and GNSS-ZTD is 3.56 mm, which is close to GNSS-PWV (3.74 mm), and is far superior to GPT3-PWV (11.12 mm).

Repetitive texture detection of building facade constrained by baseline

JIA Chen, LIU Xinyi, ZHANG Yongjun, ZHU Xianzhang, REN Weicheng, HE Qing, FENG Yougui

2023, 0(3):  49-54.  doi:10.13474/j.cnki.11-2246.2023.0071

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Repeated texture is one of the most important features in building facades. How to automatically detect repeating textures from facade images is an important part of building facade analysis. This paper proposes a new Baseline Constrained Texture Detection Method to automatically detect the exact location and size of repeating objects. The method first uses Bayesian adaptive superpixel segmentation to construct a superpixel adjacency map, and then separates the wall by calculating chromatic aberration to obtain candidate objects. Secondly, extract straight lines from the original image, and perform preprocessing such as normal classification and line segment clustering on the obtained straight lines. Finally, texture repair is performed based on prior knowledge of building facade structure. The experimental results show that the proposed method can effectively detect the position and size information of repeated textures when detecting repeated textures whose geometric shapes are rectangles, and repair the occluded repeated objects.

A multi-granularity spatio-temporal object model of site pollution environment

JIANG Huizhong, ZHANG Jianqin, JIA Hongxia, LI Xinzhi, LI Xingchen, YUAN Quan

2023, 0(3):  55-60.  doi:10.13474/j.cnki.11-2246.2023.0072

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At present, the research on polluted sites mainly focuses on the pollution situation and its development status. There is a lack of a relatively complete expression for the physical characteristics of polluted sites, and it is difficult to visualize the multi-dimensional information of polluted sites. Relying on the construction idea of multi-granularity spatio-temporal object model, this paper studies and constructs the spatio-temporal object model of multi-granularity site pollution environment, abstracts the pollution site information entity into a data model, and then describes and visualizes the relevant characteristics of its spatio-temporal entity to realize the pollution site. The integration and fusion of the full-spatial information big data based on the implementation of verification is carried out by taking a steel plant in Chongqing as an example. The experimental results show that the multi-granularity spatio-temporal object modeling of the site pollution environment can efficiently express the multi-dimensional characteristics of the polluted site, display the information of the polluted site more comprehensively, and provide technical support for the precise management and control of the polluted site, pollution assessment and restoration.

Data fusion framework of community intelligent parking from the perspective of scene

ZHANG Shu, SHI Lihong, ZHAO Xizhi

2023, 0(3):  61-66.  doi:10.13474/j.cnki.11-2246.2023.0073

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In the context of national wisdom community construction, wisdom parking has become an important element of wisdom community construction. The current community parking management wisdom is generally low, the main root cause of which is the failure to form the dynamic integration and utilization of data resources such as IOT data and scheduling command data. In this paper, facing the demand of community parking management wisdom, for the problems of scattered parking functions, insufficient visualization ability and large differences in data resources, we propose the framework of wisdom parking multimodal data dynamic fusion by studying the wisdom parking scene and related data flow, and implement the application in the community, which solves the practical problems in the parking process and meets the expansion of multimodal data fusion technology in the community parking scene and the wisdom It meets the need for the expansion of multimodal data fusion technology in the community parking scene and the continuation of the construction of intelligent parking, and improves the scientific and intelligent level of urban parking management.

Trajectory similarity measurement model considering geographic semantics

ZHOU Huijun, LUO Shijia, JIANG Heping, ZHANG Jing

2023, 0(3):  67-73,149.  doi:10.13474/j.cnki.11-2246.2023.0074

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The motion behaviour of moving objects is often influenced by the geographical environment in which they are located. In response to the current situation that existing trajectory similarity analysis often fails to take into account the geographical environment, a multiple motion feature trajectory similarity measure that takes into account geographical semantics is proposed. The method is based on a data cube that extends to the temporal level, and symbolises the geographic semantics and motion features of the trajectory sequence. Finally, this similarity measure is combined with spectral clustering to explore the motion behaviour and patterns of moving objects, and the validity and advantages of the model are verified using real data.

Trans2Vec: a representation learning framework for large-scale urban road networks coupled with vehicle movement patterns

DENG Min, CHU Guowei, CHEN Kaiqi, SHI Yan

2023, 0(3):  74-78.  doi:10.13474/j.cnki.11-2246.2023.0075

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Efficient learning of representation of urban road network information is an important project for embedding various deep learning models to intelligently solve downstream traffic tasks. However, the existing learning framework are difficult to effectively couple the topology information of the urban road network and the transfer mode information carried, and cannot accurately match the characteristic requirements of downstream traffic tasks. In this reason, this paper develops a multi-view roaming segment representation vector learning framework, which takes the vehicle movement pattern as the core, integrates the topology structure for heterogeneous walk, and realizes the complete and efficient information embedding of large-scale road network. In the experimental part, taking Shenzhen as the case area, the effectiveness and advanced nature of the method in this paper are verified through the full urban road network and actual vehicle travel data.

Subsequent processing of deformation data of miniature ground-based interferometric radar

ZHANG Lingzi, ZHANG Tao, ZOU Jingui

2023, 0(3):  79-83,127.  doi:10.13474/j.cnki.11-2246.2023.0076

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Based on the micro-ground-based interferometric radar developed by School of Geodesy and Geomatics of Wuhan University, For the deformation data of Chongqing Laijia Bridge obtained by micro-ground-based high-speed real aperture interferometric radar, the subsequent processing method of deformation data is studied. Aiming at the problems of noise and phase fracture in deformation data due to occlusion, the processing method is proposed to solve them. On the noise problem, the denoising effects of various filters are simulated and compared, and the conclusion that the wavelet transformfilter has the best effect is obtained. In the phase fracture problem, a phase fracture detection and repair algorithm based on time-frequency characteristics of deformation data is proposed to realize the automatic treatment of phase fracture problem, and the effect is remarkable.

Integrated detection of rail transit building limit based on mobile laser scanning

HUANG Xi, YAO Lianbi, YANG Lujing

2023, 0(3):  84-88.  doi:10.13474/j.cnki.11-2246.2023.0077

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Mobile laser scanning can quickly obtain 3D coordinate data on the surface of the measured object, and has been gradually applied to survey projects of rail transit engineering in recent years. In order to solve the problem that the boundary detection research of different rail transit is scattered, which is not conducive to engineering practice, this paper introduces an integrated detection scheme for clearance gauge of rail transit based on mobile laser scanning technology, develop a track laser scanning and detection(TLSD) system containing a detection process for data acquisition, processing and analysis and current normative standards of clearance gauge, which can be used for the clearance gauge detection of different rail transit. The results of an engineering case show that TLSD system has the advantages of efficient detection, automation, and visualization of results.

Study on the scale of 3D real scene for demarcation and calibration of ecological protection red line

CHEN Guang, GAO Linying, ZENG Yixiao, CHEN Liangchao

2023, 0(3):  89-93.  doi:10.13474/j.cnki.11-2246.2023.0078

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The demarcation and calibration of ecological protection red line is faced with problems such as irregular boundary, fragmentation and long extension. With the real, three-dimensional and sequential characteristics of 3D real scene, it will be effective to assist the boundary verification and pre-labeling key points. This paper takes the scale characteristics of 3D real scene as the research perspective, analyzing data acquisition accuracy, content and coverage. Considering the scale of base map that required by ecological protection red line demarcation and calibration, we analyzed its relationship to the scale characteristics of 3D real scene, and puts forward the application idea of integrated multi-scale 3D real scene model. Finally, taking the demarcation and calibration of the ecological protection red line of Zhaomushan Forest Park in Chongqing as an example, the application of multi-source and multi-scale 3D real scene data in different links is analyzed. We find it effectively improves the scientific and efficiency of our work and will be the foundation for ecological protection red line monitoring and supervision.

Vehicle clearance based deep learning for oblique 3D model

DING Lele, LIU Yanfei, MENG Fanxiao, ZHANG Tao, WANG Zhen, PAN Yuming

2023, 0(3):  94-98.  doi:10.13474/j.cnki.11-2246.2023.0079

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To solve the texture mapping problem caused by the moved car in oblique 3D model, the vehicle clearance method based on deep learning (VCDL) is proposed in this paper. In the proposed method, the vehicles are detected based on deep-object-detection CNN, obtaining the location of the vehicles. And then the vehicles are removed from the model based on deep image inpainting network and fills road textures automatically. Compared with hand-craft vehicles clearance based on Photoshop, the method proposed in this paper can effectively improve the efficiency.

Rapid inspection on installation quality of temporary support frame in Winter Olympic venues

HE Yifeng, ZOU Jingui, GONG Xiaoqiang, ZHANG Lan

2023, 0(3):  99-103.  doi:10.13474/j.cnki.11-2246.2023.0080

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Most of the infrastructure for the 2022 Beijing Winter Olympics are temporary facilities,which are mainly built on scaffolding. Bolts are required for pinning and linking of "skeletons". However, there are hundreds of thousands of bolts in the entire venue, which means the manual detection is not realistic.Therefore, it is urgent to build a system that can automatically and real-timely detect the installation quality of the bolts on the support frame. A detection method of bolt installation quality based on Faster RCNN target detection network is proposed in this paper. In addition, a support frame safety detection software and four-camera combined hardware equipment are developed independently, which greatly improves work efficiency. The strategy not only realizes automatic safety inspection, but also ensures more than 97% detection accuracy, ensuring the safety of temporary facilities for the Winter Olympics.

Road collapse analysis based on InSAR and integrated physical survey methods

DONG Gengzhi, XING Wentai, ZHOU Cheng, CAI Yongdong, ZHANG Hongguang

2023, 0(3):  104-110.  doi:10.13474/j.cnki.11-2246.2023.0081

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Urban road subsidence is a key concern in recent years, involving urban road underground pipelines, water and soil quality and other factors, with hidden, sudden and destructive, so timely detection and investigation of hidden dangers is very necessary. There are a variety of physical detection means can be used for urban road subsidence detection. This paper takes some streets in Xining city as an example, conducts a large-scale survey of them through InSAR technology, and applies the integrated physical prospecting methods such as geo-radar method, high-density electrical method and surface wave method to the key areas where settlement anomalies appear, in order to compensate for the uncertainty and limitation of single physical prospecting, and finally implements the engineering means of drilling, it establishes a method from surface to line, from line to point, from shallow to deep, according to the advantages and disadvantages of different physical prospecting methods. The system has the advantages of high efficiency and low cost, and is suitable for the fine detection of urban roads in Qinghai's wet loess areas. The feasibility of the system has been confirmed, and it is recommended that a study of the development mechanism of the disease body should be carried out to provide a more scientific basis for the prevention of road subsidence.

Frequency domain feature extraction method and application of high-resolution remote sensing image of debris flow

ZHANG Yue, ZHANG Jin

2023, 0(3):  111-115.  doi:10.13474/j.cnki.11-2246.2023.0082

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It is of great practical significance to lucubrate characteristics of debris flow on remote sensing image. The study converts high-resolution remote sensing images of different watershed regions of debris flow from spatial domain to frequency domain. Based on the spectrum analysis and frequency domain filtering, the study establishes correlation between the spectral features and partition features of the debris flow globally and locally, and identifies different watershed regions in the high-resolution remote sensing image of debris flow, finally texts it with support vector machine. The results show that making full use of frequency domain features can effectively analyze and identify different watershed regions of debris flow in addition to the spectral characteristics, and the identification accuracy is up to 95%. Thus, we can qualitative and quantitative analysis the formation process of debris flow and different areas, providing scientific basis for the prevention and control of debris flow.

Spectral model construction of urban blue roof building extraction based on Landsat 8 image

CHENG Miaomiao, WANG Shidong, ZHANG Xuejun, ZHANG Hebing

2023, 0(3):  116-122.  doi:10.13474/j.cnki.11-2246.2023.0083

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As one of the important artificial target types in the basic geographic database, the extraction of blue roof buildings is of great significance to urban environmental monitoring, illegal building monitoring, urban planning and management. In view of the low accuracy and incomplete boundary of the existing building extraction methods, and the phenomenon of foreign matter with the same spectrum and different spectrum of the same object. Taking Luoyang as the research area, according to the principle of different spectral characteristics of different ground objects, a new spectral model which can enhance the blue top information and weaken the information of other non target ground objects is constructed in this paper. Firstly, the Landsat 8 image to be detected is radiometric calibrated and atmospheric corrected to obtain the surface reflection eigenvalue image after removing the atmospheric influence. Secondly, the samples of a certain number of pixels are collected for the blue features in the image and other interfering features that are difficult to distinguish from the blue features, and the spectral curve is generated. The band addition, difference and positive and negative processing are used to construct a new spectral index that can enhance the information of the blue features and weaken the information of other interfering features. Finally, the density segmentation method is used to obtain the most appropriate threshold range for extracting the blue top building, and then extract the blue top building in the image. The results showed that the overall classification accuracy of the new spectral index model is 94.46%, the Kappa coefficient is 0.889 2, the accuracy rate is 91.95%, and the recall rate is 95.19%, which are better than the maximum likelihood method. According to the extraction results, the area of the blue roof buildings in the urban area of Luoyang city is 16.28 km², accounting for 0.564% of the area of the study area and 0.107% of the total area of Luoyang city. The results show that this method has better extraction effect and accuracy than the maximum likelihood method, and has certain advantages and practicability.

Enhanced display of 3D real scenes combined with oblique images

ZHANG Yingdong, ZHAO Jun, ZHOU Shengchuan, HU Zhenbiao, HU Haibin

2023, 0(3):  123-127.  doi:10.13474/j.cnki.11-2246.2023.0084

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Aiming at the problems of model breakage, texture deformation, suspended objects and low detail performance in 3D real scenes in near-ground perspective or when facing complex and special objects, this paper proposes a scene-enhanced display method. Using the corrected undistorted image, find the target image that matches the most similar to the scene and superimpose it on the 3D model accurately to complete the visual fusion and natural transition between the 2D image and the 3D model. And it realizes the dynamic scheduling and real-time rendering of images during the 3D roaming process to support the continuous enhanced display of super large scenes. Practices show that this method can not only make up for the insufficient visualization of the realistic 3D model and improve the visual browsing effect, but also can combine the latest oblique images to enhance the currency of the scene expression, thereby enhancing the promotion and application value of 3D real scene. The research results can contribute to the development of natural resources management, land and space planning, emergency disaster relief, urban governance and other fields.

Avector data contour adsorption algorithm considering shape of node-associated edges and similarity of proximity links

HAO Jun

2023, 0(3):  128-132,177.  doi:10.13474/j.cnki.11-2246.2023.0085

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In this paper, we design and implement a vector data contour adsorption algorithm considering shape of node association edges and similarity of proximity links to address the inconsistency between current mapping-intensive production and future holographic mapping data construction framework data and production data. The adsorption rationality generalization and efficiency stability of the algorithm are verified by random frame node displacement perturbation experiments and data partitioning incremental experiments. The algorithm effectively avoids repeated spatial query operations by establishing a point and line coordinate sorting index dictionary and many other methods, designe fast same-first-tail link extraction based on bi-directional link table and link direction approximation principle, get rid of fixed distance threshold limitation by link similarity function, established fields of nodes and links move, a fully automated vector data contour adsorption algorithm with symbiosis of node morphological adsorption and similar link adsorption is developed finally which contains high application value and application prospects.

City-level high-precision modeling technology integrating laser point cloud

ZENG Zhengxiang, HE Jingjing, ZHANG Jing

2023, 0(3):  133-138.  doi:10.13474/j.cnki.11-2246.2023.0086

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At present, the problem of real scene 3D modeling lies in the deformation of some ground object models and the fuzzy texture at the bottom of buildings caused by the missing image. In view of the shortcomings and defects of oblique photography and vehicle-borne LiDAR point cloud data sources in the construction of high-quality and high-precision urban 3D model, this paper explores the main technical process and method of using TerraSolid software to merge the point clouds obtained from the two and then model. The results show that the laser point cloud makes up for the geometrical structure of the oblique photogrammetry blind area, making the ground of the 3D model more smooth, and the edges and corners of the bottom of the building more sharp and clear. The organic combination of vehicle-borne LiDAR point cloud and oblique photography with complementary advantages can effectively make up for the defects of using a single data source to make a 3D model and improve the precision of the model.

Analysis of the influence of different weighted models on dynamicSPP positioning performance in urban complex environment

FU Hongbo

2023, 0(3):  139-143.  doi:10.13474/j.cnki.11-2246.2023.0087

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In complex urban environment, satellite positioning is seriously affected by non-line-of-sight signals (NLOS) due to the occlusion of buildings. The weighted model of random error of measured value is the key link of satellite positioning, which can reasonably distribute the role of each satellite in the calculation. Therefore, the weighted model is often used to alleviate the influence of NLOS signals on satellite positioning. This paper systematically summarizes and expounds the current mainstream weighted models, and compares and analyzes the influence of different weighting models on satellite dynamic single point positioning (SPP) in the complex urban environment. The experimental results show that all the weighted models can improve the positioning accuracy to a certain extent, and the comprehensive weighted model has the best performance.

Research on the job-housing characteristics in Central Wuhan based on easygo big data

WANG Qingguo, ZHAO Hai, WAN Jie

2023, 0(3):  144-149.  doi:10.13474/j.cnki.11-2246.2023.0088

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The analysis of job-housing characteristics can provide important guidance for the formulation of urban development planning and solving urban traffic problems. Based on the big data of easygo, this paper takes the analysis of the characteristics of job-housing distribution and the characteristics of job-housing balance of the main urban area of Wuhan from three scales:urban cluster scale, street scale, and micro scale. The study found that:① At the cluster scale, the population distribution among clusters at each time period decreases sequentially from the center to the periphery, which is consistent with the spatial pattern of the circle development and cluster layout in the main urban area of Wuhan, and each cluster is in a state of job-housing balance. ②At the street scale, 65.58% of the streets in the main urban area are relatively balanced between jobs and housing, and a few streets have the phenomenon of job-housing imbalance. ③ At the micro-scale, combined with map and POI data analysis, the population during working hours is concentrated in the vicinity of commercial districts and traffic lines, and during rest hours, the population is relatively evenly dispersed in residential areas. Taking the hot spot of population gathering during working hours as an example, the employment of the hot spot is highly concentrated, and there is an employment-oriented job-housing imbalance. As the distance increases, the job-housing distribution tends to be balanced.

Monitoring and evaluation of high-standard farmland based on geographical conditions

YUE Yongsheng, HE Yongkang, LUO Zhiyuan

2023, 0(3):  150-154.  doi:10.13474/j.cnki.11-2246.2023.0089

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“Non-grain” and utilization monitoring are important contents of utilization management after construction of high-standard farmland. Evaluation indexes are constructed from four aspects in this paper:natural attribute, ecological attribute, location attribute and non-grain, and the index weight are determined by Delphi method. Overlaying the geographical monitoring data on the basis of high-standard farmland plots, the index values are obtained through spatial analysis to monitor and evaluate the current situation of high-standard farmland construction and utilization. The results show that the indexes of location attribute and "Non-grain"are relatively good, and that of natural attribute and ecological attribute are not good with the poor performance of the ratio of soil organic matter content and the effectiveness of shelter belt in them. The index system established in this study is reasonable and effective, and the method of index data acquisition is feasible, which can achieve the goal of monitoring and evaluating the effectiveness of high-standard farmland construction.

A construction method of “one base map” of forest resources using data fusion

CHEN Chao, TAO Yang, HE Chunxiao

2023, 0(3):  155-159.  doi:10.13474/j.cnki.11-2246.2023.0090

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The construction of "one base map" is the premise of natural resources investigation and monitoring. Based on the third national land survey, survey data of forest resources planning and design, this paper studies the construction process of "one base map":after the joint intersection of the two sets of data, the fusion data considering both graphics and attributes is obtained; Different fusion methods are adopted for small patches with an area of less than 100 square meters and between 100~400 square meters; Finally, the long and thin spots and the remaining small spots are checked and processed manually. Experiments show that the fusion method in this paper can eliminate small patches and form base map data based on land survey data and taking into account the special attributes of class II survey, so as to lay a foundation for the follow-up investigation and monitoring of natural resources. Experiments show that the fusion method in this paper can eliminate small patches and form base map data based on land survey data and taking into account the special attributes of forest resources, so as to lay a foundation for the follow-up investigation and monitoring of natural resources.

A multi-factor automatic pre-marking method for ecological protection red line survey and demarcation standards

GAO Linying, WU Menghua, ZHOU Zhiyong

2023, 0(3):  160-164.  doi:10.13474/j.cnki.11-2246.2023.0091

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Ecological protection red line calibration is an important measure to ensure the accurate implementation of ecological protection red lines, and an important means to practice the important concept of "lucid waters and lush mountains are invaluable assets". This paper proposes a multi-factor ecological protection red line demarcation standard. The automatic pre-labeling method, by establishing the minimum computing unit at the boundary of the ecological protection red line and defining its area attributes, then evaluates and calculates its topographical features, road accessibility, and the frequency of human activities, and finally obtains a large-scale scene and a large-scale ecological protection red line pre-marked areas for boundary stakes and signage points. Taking Chongqing's ecological protection red line as the test area, it is verified that this method can achieve good results, improve the scientificity and rationality of boundary piles, signage points and layout density, reduce production costs, and have the characteristics of high efficiency and high degree of automation.

Efficient solution of large-scale MMTSP problem based on Tyson graph

ZHANG Yongliang, WANG Jiarun

2023, 0(3):  165-172.  doi:10.13474/j.cnki.11-2246.2023.0092

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Aiming at the problem of uneven task division and low computational efficiency in large-scale MMTSP,An efficient computational framework based on Tyson digram is proposed.Firstly,based on the proposed upper and lower convex hull alg orithm of discrete points,the Tyson digram is constructed quickly. Secondly,based on the proposed high point ignored method,the task division of MMTSP is completed quickly. Finally,the simulated annealing algorithm for sin gle TSP is used to sovle the large-scale MMTSP problem efficiently.To further improve the efficiency,some parts of the framework are based on GPU,So the task partition design of GPU parallel accelerated computing is proposed. Combine with software level a framework of software and hardware coaccelerated computing is proposed.Experiments show that,this algorithm has great advantages in accelerating optimization and balancing task division,the calculation results and efficiency are better than other two algorithms, after software and hardware coacceleration,the efficiency can be further increased by about 10 times.

Application of virtual simulation teaching platform in digital mapping training based on the combination of competition and course

DENG Xinjie, JIANG Shuhui, GUO Baoyu, WU Peng, LEI Yuanfeng

2023, 0(3):  173-177.  doi:10.13474/j.cnki.11-2246.2023.0093

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With the upsurge of new techniques and instruments in the field of survey and mapping and the development of enlarged enrollments of vocational colleges, it shows sharp challenges of training sites and equipment resources for the course "Comprehensive Training of Digital Mapping". This paper actively explores the utilization of educational informatization, especially virtual simulation technology. Virtual reality (VR) training platform is an effective measure to integrate modern information technology into practical training teaching. In this platform, the working scene for digital mapping projects has been reconstituted through VR and modeling techniques and then is integrated with surveying and mapping simulation intelligent equipment. That is conducive to expanding the content and flexibility of digital mapping training and improving the quality of training teaching. In this paper, the VR simulation platform which has been applied in the national digital mapping competition for geographic information vocational college students has been introduced to the comprehensive practical training of digital mapping to puts forward some suggestions for improvement under the background of "promoting teaching through competition".

Correction method of sounding error of multi-layer constant gradient sound velocity profile

FAN Xiaotao, DU Zedong, YE Fei, ZHENG Yahui, MA Yaochang

2023, 0(3):  178-182.  doi:10.13474/j.cnki.11-2246.2023.0094

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Sound velocity profile (SVP) is an important parameter of multibeam sounding. However, in the complex area of water, sound velocity profile is often used to encrypt observations or interpolate observations, but there are always varying degrees of refraction errors. In order to enhance the quality of observation data, it is usually corrected by post-processing method. At present, the research tends to focus on acoustic tracking algorithm and how to enhance and invert SVP quality and methods. This paper analyzes the influence of sound velocity on sounding system and deduces how to build the constant gradient equivalent sound velocity model, and puts forward the constant gradient sound velocity profile correction model, which solves the influence of sound velocity substitution error or sound velocity profile inaccuracy well. The experimental results show that the model has better consistency in the topographic edge data of post-processing analytical data, and the quantitative results are better than the traditional sound velocity profile correction algorithm.