Table of Content

25 April 2023, Volume 0 Issue 4

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Continuous multi-temporal monitoring of algae pollution in Nanwan Lake based on high score data

WEN Ye, WANG Songyan, ZHANG Huan

2023, 0(4):  1-5,15.  doi:10.13474/j.cnki.11-2246.2023.0095

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Algae pollution affects water quality and causes significant damage to the ecological environment. In the study of lake green algae pollution, domestic high-resolution and wide-range data are rarely applied. In this paper, the high-spectrum and wide-width data of GF-1 and GF-6 are comprehensively used to monitor the pollution of green algae in Nanwan Lake by using the normalized vegetation index and the normalized vegetation index introducing the red-edged band, and the pollution time and range evolution are determined. The analysis yielded: ①On July 20,2020, there is green algae pollution. ②On August 2 and 3,2020,there is no green algae pollution. ③On August 4,5 and 9,2020,green algae recurred at a bend downstream. The pollution and recurrence of green algae in Nanwan Lake are consistent with the actual situation, indicating that the high-score data has potential for application in the monitoring, extraction accuracy and efficiency of green algae in short-time lakes.

Dynamic changes of Yanhu Lake in Hoh Xil area on Qinghai-Tibet Plateau in recent 30 years and analysis of its influencing factors

GUO Ziying, LIAO Zhongping, LIU Baokang, XU Zhengdong, LIU Ming

2023, 0(4):  6-9.  doi:10.13474/j.cnki.11-2246.2023.0096

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The lakes on the Qinghai-Tibet Plateau are sensitive indicators of global climate change and have a strong feedback effect on global climate change. Due to the breakwater of Zhuonai Lake, the Yanhu Lake of Hoh Xil, located in the hinterland of the Qinghai-Tibet Plateau, is expanding rapidly, which not only harms the surrounding grassland vegetation and the permafrost flowing through, but also interferes with the normal operation of the Qinghai-Tibet railway and the Qinghai-Tibet highway. In this paper, multi-source remote sensing monitoring means are used to monitor the Yanhu Lake in Hoh Xil area in recent 30 years, and the dynamic changes of the area of the Yanhu Lake are extracted from the trend of temporal and spatial changes, and the causes are analyzed. The results show that: ① The collapse of Zhuonai Lake in September 2011 increased the Yanhu Lake of Hoh Xil by 178.535 km² from 1990 to 2020.② Since the completion of the diversion project of Yanhu Lake in Hoh Xil area in 2020, the area of the Yanhu Lake has been effectively contained and will be reduced to 191.145 km² in 2021. ③ The shoreline of the Yanhu Lake has expanded significantly in the southeast and southwest from 1990 to 2020, and the biggest change is that the eastern part of the Yanhu Lake has become an island from the peninsula that once stretched into the center of the lake. ④ The area has a significant correlation with precipitation and temperature, and a weak correlation with sunshine duration and glacial melt water.

Shape changes and driving factors of Zhifu Bay in Yantai from 1975 to 2020

WANG Han, LIU Ning, XUE Yan, SUN Guiqin, WEI Xiao, XU Yandong

2023, 0(4):  10-15.  doi:10.13474/j.cnki.11-2246.2023.0097

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The bays are major places for comprehensive development and utilization of coastal zone, and study on the shape change and driving factor of the bays will help to provide a scientific basis for their development, utilization, protection and restoration. Taking the Zhifu Bay(ZFB) as the research object, its spatial information of 10 time phases from 1975 to 2020 is extracted from Landsat remote sensing images, and its shape changes, characteristics and driving factors are analyzed from four aspects: the degree of shoreline development and utilization, the area of ZFB, the shape of ZFB, as well as the distribution of centroid of ZFB. The results show that since 1975, the shape change of ZFB in the study area has been significant and complex. The development and utilization of the gulf shoreline continue to increase, and the shoreline generally moves from land to the sea; the area of ZFB gradually shinks, decreasing by 8.82 km² in 45 years, accounting for 25.99 % of the total area in 1975; the shape index of ZFB increases from 1.33 to 2.23, and the bay shape tends to be complex; during the study period, the centroid of ZFB has generally migrated to the sea by 647.79 m. In general, the reclamation for port terminals and coastal culture pond is an important reason for the changes of ZFB.

Regional ecological security pattern of Fujian and Guangdong networking project (Fujian section) based on the minimum cumulative resistance model

JIANG Shixiong, LI Xi, WANG Chongqing, CHEN Yao, WENG Sunxian

2023, 0(4):  16-22.  doi:10.13474/j.cnki.11-2246.2023.0098

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Ecological security and ecological security pattern are hot topics in regional ecological protection research, and the environmental impact assessment of power transmission line project,which is relatively insufficient to consider ecological security. This paper takes the area of Fujian-Guangdong linkage project (Fujian section) as an example, and adopts morphological spatial pattern analysis (MSPA), minimum cumulative resistance (MCR) model and gravity model to obtain the regional “source-corridor-node” ecological safety pattern. The ecological security pattern of “source-corridor-node” is obtained by using morphological spatial pattern analysis (MSPA), minimum cumulative resistance (MCR) model and gravity model, and finally the ecological security impact of power transmission project construction is obtained. The results show that, in 2020 and 2021, the ecological source areas in the study area accounted for 47.29% and 40.16% of the regional area, respectively, and the ecological source areas are concentrated in the central and western parts of the study area. There are 21 important ecological corridors with an overall spatial distribution of triangle; four ecological safety protection areas are distributed in the study area, for Damao mountain, Fengtou reservoir, Gaofeng valley and Egret forest park, among which Damao mountain and Egret forest park have a large proportion of ecological “source-corridor-node”. In 2020 and 2021, 3 ecological nodes, 52.09 and 58.46 km of ecological corridors,185.63 and 154.42 km² of ecological source areas are involved in the 2 km ecological impact zone of Fujian-Guangdong linkage line, respectively. The results of the study clarify the key ecological security protection zone of Fujian-Guangdong linkage project (Fujian section) and provide a scientific basis for formulating ecological protection measures.

A multi-level regional encryption method for remote sensing images by considering differences in texture features

DENG Min, WANG Jing, TANG Jianbo, DING Chen, YANG Xuexi, LIU Huimin, LIU Baoju

2023, 0(4):  23-28.  doi:10.13474/j.cnki.11-2246.2023.0099

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To address the security problems of high-resolution remote sensing image in the process of network transmission, data sharing and application, this paper proposes a multi-level regional encryption method for remote sensing images by considering differences in texture features. First, the large data volume of remote sensing image is divided into blocks and each sub-image block is classified into simple, medium and complex types according to the complexity of texture features. Second, the cipher sub-image blocks are obtained by encrypting the sub-image blocks with chaotic systems of different dimensions for different types of sub-image blocks. Finally, combine the cipher sub-image blocks to obtain the overall encrypted cipher image. By using real remote sensing image for experimental analysis, the results show that the proposed algorithm not only can well achieve the information hiding of remote sensing image, but also can balance the security and time complexity of encryption, which has potential application value in the field of high-resolution remote sensing image data sharing and image processing for mass application in the era of big data.

Perspective transformation method for position-attitude calculation of crowdsourcing aerial panoramic imaging

PU Hongyi, LI Feng, XU Zheng

2023, 0(4):  29-34,40.  doi:10.13474/j.cnki.11-2246.2023.0100

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For the lack of position-attitude information, crowdsourcing aerial panoramic imaging is not able to precisely locate and orient in the geographic information space.A perspective transformation-based method of position-attitude calculation is proposed. First of all, the principle of proposed method is illustrated and the calculation scheme is designed. Secondly, spherical panorama model is constructed and “flat-sphere-flat” model transformation is implemented by perspective transformation Meanwhile, iterative reweighted least squares(IRLS) is designed for position and attitude calculation based on the deformation characteristics of model transformation. Finally, feasibility and reliability of the method are experimentally verified by using aerial panoramic images of Zhifang reservoir as a case.

Study on SLIC segmentation and region merging method of low-altitude remote sensing images with fused elevation information

ZHAO Zongze, FANG Mingyuan, GAO Zhao, WANG Shuangting

2023, 0(4):  35-40.  doi:10.13474/j.cnki.11-2246.2023.0101

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Aiming at the problem that SLIC segmentation algorithm does not consider elevation information in remote sensing image segmentation, which leads to poor segmentation effect of some features, this paper proposes the SLIC super-pixel segmentation of remote sensing image fused with elevation information and the double-threshold region merging method based on elevation grading. Firstly, the elevation information is introduced into the initial clustering segmentation threshold to obtain the initial segmentation result with dependence on both spectral gradient and elevation gradient. Then, the data structure of neighborhood array is adopted on the basis of pre-segmentation to establish the similarity metric by weighting the spectral information of different regions combined with elevation information. Finally, the graded elevation threshold is set, and different merging threshold weights are set according to the elevation difference between different regions perform region merging. The proposed method is validated by using the low-altitude remote sensing image data with fused elevation information and the dataset provided by the international society for photogrammetry and remote sensing, and the results show that good segmentation results are achieved by introducing elevation information in the super-pixel segmentation and region merging method based on spectral information.

Identification method of urban villages with improved composite dictionary considering multi-resolution features

XING Ruoyun, RAN Shuhao, GAO Xianjun, YANG Yuanwei, FANG Jun

2023, 0(4):  41-48,48.  doi:10.13474/j.cnki.11-2246.2023.0102

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Urban village is a special type of urban settlement, and accurate and effective monitoring and identification of urban village is conducive to achieving coordinated development of urban and rural areas and optimizing the ecological environment. Existing object-oriented urban village identification methods usually require a large amount of sample data, resulting in high training cost and low data update efficiency. In order to solve the problems, a composite dictionary urban village identification method considering multi-resolution characteristics is proposed. Firstly, we use dense grid sampling to extract SIFT global features, and fuse them with multi-resolution color vector angular histogram features to form a visual dictionary. Then we use the image representation as a visual word frequency histogram. Finally, the random forest classifier is classified to realize the identification of urban villages at scene scale. The overall accuracy of the proposed method reaches 90.08% and the Kappa coefficient reaches 80.16%. It is 8.99%, 3.51%, 4.78% and 2.28% higher than that of SURF, SIFT, VGG16 and ResNet50, respectively.

DeepLabV3+ improved algorithm for national building recognition in traditional village aerial images

CAI Jun, WEN Riqiang, JIANG Wei, YAN Jiao, LU Lijuan

2023, 0(4):  49-53.  doi:10.13474/j.cnki.11-2246.2023.0103

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Aiming at the problem that traditional village aerial images are difficult to accurately identify national buildings,this paper analyzes the recognition results of three deep learning pixel classification algorithms. The recognition accuracy of national buildings of DeepLabV3+,U-Net and PSP-Net algorithms are 0.957,0.929 and 0.943 respectively. The DeepLabV3+ algorithm is used to test six typical areas of traditional villages. The main problems in the test results include: some roads and site areas in traditional villages are marked as national buildings,and the edges of the marked national buildings area are serrated. In order to accurately identify the national buildings in traditional villages,the national building identification results of DeepLabV3+ algorithm are improved based on ArcGIS software platform. The improved post-processing contents include marked area filtering and marked area boundary cleaning. The improved post-processing results can optimize the smoothness of the edge of the national architecture marked area of the traditional village aerial image on the basis of ensuring the accuracy of national architecture recognition.

Remote sensing monitoring and analysis of territorial space changes in Inner Mongolia in the past 30 years based on the major function-oriented zoning

WANG Junzhi, DOU Yinyin, XUE Zhizhong, GUO Changqing, CHI Wenfeng

2023, 0(4):  54-58.  doi:10.13474/j.cnki.11-2246.2023.0104

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The spatio-temporal patterns of territorial space development intensity in Inner Mongolia in the past 30 years (1990—2020) are investigated by integrating geographical national data and land use/cover data with a 30 m resolution. Then, the changes in territorial space were compared before and after the implementation of major function-oriented zoning. The impact of the major function-oriented zones on their main components is evaluated further. The results indicated that the intensity of territorial space development in Inner Mongolia showed a trend from the acceleration of 1990—2010 to the slowdown of growth in 2010—2020. The area of artificial construction land has expanded by 42% in the past 30 years. The increase in artificial construction land and agricultural land has reduced the amount of natural land. Since the implementation of major function-oriented zoning, the area of artificial construction land within the key development zone has increased. The area of agricultural land in the main producing zone for agricultural products changed from growth to reduction. The natural land area in the key ecological function zone declined. The outcomes are crucial for achieving the goals of “Beautiful Inner Mongolia” and advancing regional ecological civilization.

Research and application of damage detection of highway billboard damage based on vehicle-mounted remote sensing image

ZHU Jianwei, LI Chaokui, ZHOU Xinshao, ZHAO Dingying, FU Kaihong

2023, 0(4):  59-63,98.  doi:10.13474/j.cnki.11-2246.2023.0105

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There is an inefficient and dangerous problem in the current manual inspection method of highway billboard management, and a new method of highway billboard inspection is proposed with the identification of damaged images of vehicle remote sensing billboards as the technical support. Based on the improved SIFT algorithm and the RANSAC algorithm, the method passes the discrete cosine transform before the extremum points of the SIFT Gaussian differential space are selected. Transform converts the light intensity data of the image into spectral data and performs a gating operation to screen out the high frequency coefficients while improving the quality of the initial set of inner points. Using RANSAC to calculate the perspective transformation model parameters for fine matching, and then adapt the matrix alignment to the opposite, the sum of the two images that are different from each other is determined, and the different connectivity domains are marked and extracted. Experimental results show that the performance of the proposed improved algorithm in the detection of billboard damage is robust, and the detection accuracy is more than 80% under the interference of various conditions, which meets the application requirements of this direction. The research results provide a new original technical support for Chinese highway management and related departments to identify, update and maintain highway billboards in a timely and effective manner.

Railway slope monitoring using GNSS precise point positioning and inter-system bias

HE Yilei, ZHANG Yunlong, ZHANG Guanjun, HU Jinmin, CHEN Xusheng

2023, 0(4):  64-70.  doi:10.13474/j.cnki.11-2246.2023.0106

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Currently, BDS-3 has been fully completed and new signals with better performance have been broadcast to provide services. The influence of ISB should be taken into account when applying PPP in automated monitoring under railway sheltered environment. This paper takes the monitoring of mountain slope engineering of a railway tunnel as an example. The BDS-2+BDS-3 combined PPP model with ISB is introduced in detail, and the ISB modeling method of octave polynomial+autoregressive integrated moving average model is proposed. The accuracy of the model is verified, and the stability of the slope monitoring point is analyzed. The research shows that when BDS-2 (B1I, B3I) and BDS-3 (B1C,B2a) PPP is used, ISB can reach hundreds of nanoseconds, which can not be ignored, but it has short-term stability. The model is modeled with 14 d ISB series, when the forecast time is 1 d, the model has high fitting accuracy and good consistency. In addition, considering the BDS-2+BDS-3 ISB in the railway sheltered environment, the positioning accuracy and calculation efficiency can be effectively improved. The long-term static deformation monitoring of railway slope can be realized, and the monitoring accuracy can reach millimeter level.

BDS-3 quad-frequency long baseline positioning algorithm considering ionospheric delay

Lü Zhen, WANG Zhenjie, LIU Jinping, ZHAI Jianpeng, ZHOU Hao

2023, 0(4):  71-78.  doi:10.13474/j.cnki.11-2246.2023.0107

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Considering that ionospheric delay in long baseline positioning can affect the positioning accuracy, this paper proposes a quad-frequency ionosphere-free (IF) combination method based on BDS-3 four-frequency signals (B1C/B1I/B2a/B3I), which eliminates the ionospheric delay error by using the combined ionosphere-freeobservations and constructs the positioning equation by combining the ambiguity-corrected extra-wide-lane or wide-lane combination observations, so as to estimatethe raw narrow-lane ambiguity and baseline coordinates. The experiments are conducted to compare the positioning accuracy of quad-frequency IF combination method and ionospheric delay parameter estimation method based on GB-FCAR modelusing BDS-3 quad-frequency data. The results show that when long baseline is over 500 km,the quad-frequency IF combination method can eliminate ionospheric delay error. Compared with the ionospheric delay parameter estimation method, the positioning accuracy of the quad-frequency IF combination method can reach the decimeter level in both horizontal and vertical directions,the improvement can reach more than 35% and 40% respectively,which significantly improves the positioning accuracy. The relative positioning accuracy can reach 1×10^-9 m, which meets the relative positioning requirements of long baselines.

The conceptual connotation,characteristics and discrimination of resilient PNT

MING Feng, YANG Yuanxi, ZENG Anmin, REN Xia

2023, 0(4):  79-86,176.  doi:10.13474/j.cnki.11-2246.2023.0108

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PNT (positioning, navigation and timing) has become an information technology which is closely related to our daily life and economic and social operations. Resilient PNT describes the ability of a PNT system to resist, adapt, and recover from disturbances in a timely manner. Due to the significant increase in the inhabited vulnerability of space-based PNT systems and the threat of man-made interference, resilient PNT has become a research hot spot in Europe and the United States. Firstly, the related concepts of reliability and resilience are distinguished and analyzed, and the reasons and trends of the development of complex system performance indicators from traditional reliability to resilience are analyzed in this paper. Then, the concept of resilient PNT system is discussed, and its characteristics and indicators are mainly analyzed, and the relationship between the resilience and other indicators such as accuracy, integrity, continuity and availability is given. Finally, relevant conclusions are given.

Spatial optimization model for sensor network planning: considering the line-of-sight coverage in urban outdoor areas

ZHANG Xiaoyu, MA Xiaoya

2023, 0(4):  87-92,127.  doi:10.13474/j.cnki.11-2246.2023.0109

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In the location problems,the services of some sensors (such as surveillance cameras) are not propagated due to the obstruction of obstacles such as buildings,which is typically defined as the line-of-sight (LOS) effect. Maximizing effective service coverage with minimal network deployment and costs is a challenge in the optimization of sensor network planning. In this paper,to consider the LOS effect in the optimization of sensor network,the classical maximal coverage location problem (MCLP) model is improved by a GIS visual analysis technology to simulate the LOS effect of service coverage. And coupled with a genetic optimization algorithm to achieve layout optimization.The developed model in this study is applied to a spatial optimization problem of surveillance cameras in a city block to validate its performance. The experimental results show that our model can significantly improve the effective service coverage of the surveillance sensors by about 52.31% in the study area compared with the comparison optimization model that does not consider the LOS effect.

Matching pair retrieval method of UAV images based on the graph structure bag of words model

LIU Sikang, GUO Bingxuan, JIANG San, YAN Maosheng

2023, 0(4):  93-98.  doi:10.13474/j.cnki.11-2246.2023.0110

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Matching pair selection is a key technology to improve feature matching efficiency and 3D reconstruction reliability of UAV images. However, the classical tree index structure word bag model has low efficiency in finding words, low precision in similarity calculation, and high time cost in image retrieval. This study designs the navigation small world (NSW) graph index structure and TF-IDF-Match4 algorithm, and proposes matching pair retrieval method based on the Graph Structure Bag of Words (GSBoW) model. Firstly, the SIFT GPU algorithm is used to extract features of UAV images, which are used to generate visual words through hierarchical K-means clustering. Secondly, visual words are indexed by using a NSW graph index structure, which is achieved by iteratively selecting a random word and inserting it into the NSW graph, and searching its M nearest vertices that are used to build the edge connection. Finally, the NSW graph structure is implemented on GPU for nearest word searching, and match pair selection is achieved by an efficient algorithm, termed TF-IDF-Match4, for the calculation image similarity scores. The experiments are carried out using three large-scale UAV datasets and compared with the bag of words model algorithms in Colmap and DBoW. The results show that the proposed match pair retrieval algorithm can respectively achieve the speed up ratio of 45 and 18 times compared with Colmap and DBoW, which is provided matching pairs for higher accurate 3D reconstruction.

Evaluation of forest flammability based on inversion data of vegetation canopy water content

CHEN Zongjie, YANG Wunian, ZHANG Wanlin, LIU Mingxin, DONG Xiujun, HE Xianding

2023, 0(4):  99-105.  doi:10.13474/j.cnki.11-2246.2023.0111

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Frequently occurring forest fires in Liangshan county spread rapidly and are difficult to be put out. This paper proposes a method to identify forest combustion and flammablility levels by using traditional remote sensing means, relevant data of remote sensing satellite, UAV, and several selected factors such as terrain, surface temperature, vegetation, and water content. The concept of ecological water (layer) is adopted into our study of the target area to generate a spatial significance distribution on forest combustion and flammability, which can further establish an evaluation system to control and prevent forest fires.

Estimation of urban vegetation carbon storage using hyperspectral data

LI Junji, FEI Jianing, ZHOU Ting, GAO Guang, ZHAO Juejing, WU Dun

2023, 0(4):  106-110.  doi:10.13474/j.cnki.11-2246.2023.0112

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Urban vegetation is one of the important factors in low-carbon governance, and its carbon sequestration capacity directly affects urban carbon emissions. In view of the time-consuming and labor-intensive existing technology, which has a certain impact on the environment, this paper proposes a study on the estimation of urban vegetation carbon reserves based on hyperspectral data. Taking the central urban area of Baiguan street, Cao'e street and Songxia street in Shangyu district, Shaoxing city as the study area, urban vegetation is divided into four types: arbor, shrub, bamboo forest and grassland. The proposed carbon sequestration index is used to qualitatively analyze the carbon sequestration capacity of vegetation, and the biomass empirical formula is used to quantitatively calculate the carbon storage. The hyperspectral vegetation carbon storage estimation model is obtained by combining the two, which provides a new idea for the rapid estimation of large-scale carbon storage. The results show that the classification accuracy of the four urban vegetation reaches 88.10%, and the carbon fixation capacity is ranked as bamboo forest>tree>shrub>grassland.

Application of UAV image matching point clouds in monitoring of illegal land and illegal construction

QUAN Changwen, LI Zhenghong, PANG Baining, XIONG Yifei

2023, 0(4):  111-114,134.  doi:10.13474/j.cnki.11-2246.2023.0113

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At present, the monitoring of illegal land and illegal construction is mostly based on remote sensing images, it can not effectively detect the situation of building addition and construction, and so on. The use of image densely matching point clouds for extracting 3D changes of buildings is an effective way to accurately monitor “two violations”. In Guigang city “two violations” monitoring as an example, using UAV image matching point clouds as the basic data, through the depth of neural network model to extract buildings point clouds, and to detect the change of the different temporal point clouds, after superimposing the management data of natural resources, such as approval and planning, extract the suspected “two violations” spots and monitoring.

NRTK PPK aided 3D modeling analysis of image free UAV tilt photogrammetry for water conservancy projects

ZHANG Linjie, HUANG Xiao, RAO Weidong, LUO Wei, ZUO Qiang, XIONG Hao, LI Wenhui

2023, 0(4):  115-120.  doi:10.13474/j.cnki.11-2246.2023.0114

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Traditional surveying and mapping products can only provide abstract plane geometry information for water conservancy project construction,lacking authenticity and three-dimensional texture information. In order to reflect and express the construction of water conservancy projects in a real,3D and sequential way,this paper takes a water conservancy project as an example,by using Feima multirotor UAV D2000 and DOP3000 tilt photography module,the real-time dynamic differential POS based on carrier phase and post-processing dynamic differential POS image free 3D modeling of tilt photography reality for water conservancy projects is carried out. The precision comparison results of the final models show that the plane accuracy of the imageless 3D models based on the network RTK and PPK POS is equivalent,while the elevation accuracy of the model based on PPK POS is better than that of the network RTK POS. However,both models can meet the requirements of 3D model products with 1∶500 mapping scale,and both models have rich texture information,which can be used to assist the geological exploration of hydraulic engineering,safety monitoring and intelligent water conservancy construction.

Application of UAV airborne LiDAR technology in Karst identification of pumped storage power station reservoir area

ZHENG Peng, WEI Xingcan, LI Ning, LI Qiang, CHEN Jiangpan

2023, 0(4):  121-127.  doi:10.13474/j.cnki.11-2246.2023.0115

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In the Karst mountain area of southwest China, the vegetation is dense and the terrain is steep. The traditional ground Karst investigation methods are inefficient and dangerous. In this paper, the airborne LiDAR technology is used to obtain the laser point cloud and optical image data of the reservoir area of a pumped storage power station in Sichuan, and combined with the indoor interpretation and field review, regional Karst identification is carried out. The development and distribution of Karst in the reservoir area are found out, which can be divided into Karst funnel, Karst depression and sinkhole according to the Karst morphology. Based on the existing data and LiDAR data results, the elevation, slope, aspect, structure, lithology and catchment area factors of the reservoir area are extracted, and the distribution law of Karst development is analyzed. The results show that the UAV airborne LiDAR technology can accurately and quickly identify the Karst distribution characteristics in the reservoir area of the pumped storage power station, and provide a new technical means for the early survey and design of the power station.

Application of 3D LiDAR air-ground integration technology in urban heat island research:a case study of Yanzhong greenspace in Shanghai

MENG Chen, WEI Yanhao, WU Caiyan, OUYANG Linke, LI Junxiang, ZHU Yi, LIU Jialin, WEI Bensheng, JIANG Ruijiao

2023, 0(4):  128-134.  doi:10.13474/j.cnki.11-2246.2023.0116

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Urban heat island effect is one of the most prominent ecological and environmental problems during the process of urbanization. Urban green space infrastructure is one of the key elements of the city, which can effectively alleviate the urban heat island. The planning and construction of Yanzhong greenspace is an important strategy of “natural based solution” given by Shanghai to alleviate the heat island effect. Based on the air-and ground-LiDAR data which are obtained from FEIMA UAV and its corresponding sensors, as well as land surface temperature from Landsat 8 Collection 2 Level 2 dataset, we analyze the cooling effect of Yanzhong green space in Shanghai, and the 3D vegetation volume distribution pattern and its influencing factors. The main conclusions are as the following: ① There is a directional cooling effect of Yanzhong greenspace, due to the influence of the surrounding landscape pattern. The sequence of the directional maximum cooling distance is the southeast, and followed by the southwest, northeast and northwest. While the maximum of the local cool island intensity is southwest, and the minimum is the southeast. The vegetation types greatly influence the cooling effect, with the ranking of their surface temperature from tree, grassland to shrub type. ② The higher 3D vegetation volume areas of Yanzhong greenspace mainly located in the northwest where nearby the highway, and dispersedly distributed across the greenspace. The 3D vegetation volume in Yanzhong greenspace is significantly negatively correlated with the distance from the road (D_road), and significantly positively correlated with the distance from the water body (D_water), while there is no significant correlation with the distance from the building (D_fw). The optimal model of the 3D vegetation volume is V_Yanzhong=224.354 56-1.513 65D_road+0.412 85D_water.Our study provides important theoretical and practical insights for urban heat island mitigation as well as urban greenspace planning and management.

High-precision measurement method using structure light scanning and optical tracking

HUANG Gaoshuang, HUANG Guiping, ZHOU Yang

2023, 0(4):  135-139.  doi:10.13474/j.cnki.11-2246.2023.0117

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Structured light scanning measurement is one of the methods widely used in precision manufacturing. Compared with common measurement methods, it has the advantages of higher point density, point accuracy, and non-contact measurement. Aiming at the shortcomings of conventional structured light scanning measurement, such as small measurement range and time-consuming and cumbersome waypoint teaching, a measurement method combining optical tracker and structured light scanner is proposed. The optical tracker is used to measure the spatial attitude of the structured light scanner in real-time, and the scanned point cloud is converted into the same coordinate system in real-time, realizing real-time measurement of large size, high point density high precision, and non-contact measurement of the reflective surface. The test evaluates the measurement accuracy of this method. The test results show that for a large reflective surface with a diameter of 3.1 m, the best fitting RMSE between the scanning results and the digital-analog is at least 0.067 mm, which is better than the precision of 0.15 mm required for profile manufacturing and can meet the precision requirements of high-precision industrial production.

Application of 3D laser scanning technology in monitoring erosion and spalling of natural relics

ZHANG Qingyuan, ZOU Yanlong, LI Jinheng

2023, 0(4):  140-144.  doi:10.13474/j.cnki.11-2246.2023.0118

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Based on the chime hammer peak monitoring project in Chengde City,aiming at the problems of single point monitoring,low degree of automation and unable to reflect the overall shape of the peak by traditional methods,this paper uses three-dimensional laser scanning technology to monitor the chime hammer peak for a long time,and realizes the comparison of three-dimensional model data of multi-stage peaks through control measurement,point cloud data acquisition,splicing and modeling,The volume and center of gravity change of the peak are calculated,and the development trend of the peak is predicted by the volume change and center of gravity displacement extracted in the form of segmented slices. This method breaks through the limitation that the traditional measurement methods can not monitor the peak body as a whole. It monitors the peak body as a whole with non-contact,high precision,high efficiency,and uses the shape variables of the opposite and body to achieve the effect of monitoring the peak body,so as to find the more serious erosion spalling or inclined situation of the peak body,so as to provide decision-making auxiliary support for the next protection work.

Building change detection of remote sensing image based on improved DeepLabV3+

QI Jianwei, WANG Weifeng, ZHANG Le, WANG Guangyan

2023, 0(4):  145-149.  doi:10.13474/j.cnki.11-2246.2023.0119

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As an important task in the field of remote sensing, change detection plays an important role in the scenes of law enforcement inspection of satellite land image, farmland conversion. In recent years, relevant practitioners have used AI related technologies to solve the task of change detection. The common technical solution is to concatenate two images by channel dimension and use semantic segmentation algorithm to predict the change area. This paper uses the change detection dataset LEVIR-CD as experimental data,based on DeepLabV3+algorithm, improves the model structure according to the characteristics of change detection task. The siamese network uses DeepLabV3+as the backbone. This paper uses multi-level feature interaction to fully fuse image features. The results show that the improved network structure is more suitable for change detection task.

A registration method for indoor scenes point cloud based on place recognition

NIU Xuechao

2023, 0(4):  150-153,158.  doi:10.13474/j.cnki.11-2246.2023.0120

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The existing solutions have low robustness for registration between low overlap point clouds in indoor scenes. In this paper, a robust place recognition based registration algorithm is proposed. Virtual scans are generated based on the result of disjoint spaces. Global feature descriptors are extracted from virtual scans subsequently.Then the overlap area can be determined using place recognition. At last, the transformation can be obtained accurately by aligning the point cloud of overlap area. The experiments show that the proposed solution estimate accurately the transformation parameter for low overlap indoor point clouds.

Quality analysis on the image greyscale for the close-range photogrammetry based on the spectrum fusion method

ZAHNG Chen, WU Zhaofu, HUANG Jianwei, YU Min, WANG Lu, LI Shuiping

2023, 0(4):  154-158.  doi:10.13474/j.cnki.11-2246.2023.0121

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Close-range photogrammetry has been widely used in foundation pit monitoring, industrial surveying, cultural relic restoration and other fields. The monitoring accuracy affected by the image greyscale variation remains the solving problem during the long-term close-range photogrammetry. In this paper, the foundation pit monitoring of Yangzijiang River station in Section 2 of Hefei rail transit Line 5 is selected as the engineering background. Firstly, the influence of image grayscale variation on the monitoring accuracy is analyzed. And the optimal grayscale interval is determined. Then, the spectral fusion method is used for the greyscale correcting on the image with non-optimal greyscale interval. The original phase spectrum of the image is fused with the spectrum with optimal greyscale image, leading to the adjustment to the optimal greyscale interval. The matching accuracy before and after the spectrum fusion is analyzed. The experimental results show that the optimal greyscale range of the image of the highest accuracy is 139.0～173.8. After spectrum fusion, the image accuracy is improved on 43.7% to 79.5%. The reduced variation coefficient can lead to the improved data stability. This paper can provide a new solution to the problem of poor image accuracy caused by greyscale variation of long-term close-range photogrammetry.

Combined BeiDou and ground-based InSAR multi-source data analysis of maoxian landslide in Sichuan province

HE Yadong, XU Xuxiong, LI Lin, SUN Ming, HUANG Feng

2023, 0(4):  159-162.  doi:10.13474/j.cnki.11-2246.2023.0122

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Based on the typical case of Weimen town landslide in Maoxian county, Sichuan province, this paper uses crack meter and rain gauge equipment to monitor and identify the phenomenon of landslide severe sliding. The BeiDou regional network is set up to obtain real-time monitoring data. The 119.5 h continuous monitoring of the GBInSAR is used to obtain the complete deformation information of the landslide surface, and obvious deformation in the landslide is analyzed. Comparing BeiDou and GBInSAR monitoring at the same position, the results show that the deformation and velocities monitored by the two devices are basically the same. Monitoring by combining BeiDou and GBInSAR can give full play to the advantages of the two means, and analyze the landslide surface deformation information from different positions, which is of great significance for early prevention and local real-time monitoring of landslides.

CVCEEMDAN-WT-SSA algorithm of denoising the data from monitoring offshore platform by GNSS RTK

XIONG Chunbao, ZHANG Zijian, CHEN Wen, YU Lina

2023, 0(4):  163-166,171.  doi:10.13474/j.cnki.11-2246.2023.0123

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Aiming at the multi-path errors and random noise of GNSS RTK technology in the deformation and displacement monitoring of offshore platform, a combined denoising algorithm based on cross-validation improvement of complete integrated empirical mode decomposition (CVCEEMDAN), wavelet threshold (WT) noise reduction method and singular spectrum analysis (SSA). Firstly, the original signal is decomposed by CEEMDAN, and the IMF components of noise and effective signal are identified by cross-validation method. Then WT and SSA are used to denoise the noise and effective signal components respectively, and the processed signal is reconstructed to obtain the real deformation monitoring results. The results show that this algorithm is adaptive and has better denoising effect than EMD, EEMD, CEEMDAN and ACCEEMDAN-WT-SSA algorithms. It can effectively remove multi-path errors and random noise in the deformation monitoring of offshore platform, and successfully obtain the real monitoring signal results.

Long time-series of surface deformation monitoring and cause analysis in Baiyun district,Guangzhou base on SBAS-InSAR technology

DING Wei, CHEN Zhanpeng, XU Bing, FENG Zhixiong

2023, 0(4):  167-171.  doi:10.13474/j.cnki.11-2246.2023.0124

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With the advancement urbanization, the human activities, such as ground water extraction and underground project, become increasingly intensive in cities, resulting in surface subsidence, which influences people's life. To ensure the healthy and stable development of the city, it is of great significance to carry out large-scale land subsidence monitoring in urban areas. This paper uses SBAS-InSAR technology to process 176 Sentinel-1 SAR images of Baiyun district, Guangzhou, acquired from February 2016 to March 2022, and obtains the annual average deformation rate and time-series of deformation. We analyzes the causes of deformation in the study area by combining historical optical images and field investigations. The results show that the deformation is mainly related to local geological conditions, biological and chemical degradation of garbage and human activities. The maximum deformation rate exceeds 40 mm/a, and the maximum cumulative deformation exceeds 350 mm. The research provides a reference for land subsidence monitoring and cause analysis in urban areas.

Continuous cartographic generalization method supported by DTW algorithm for the continuous scale transformation of linear map features

KANG Ermei, MAO Kainan

2023, 0(4):  172-176.  doi:10.13474/j.cnki.11-2246.2023.0125

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This paper propose a continuous generalization method supported by DTW algorithm for the continuous scale transformation of linear map features. Based on the idea of scale fusion, this method takes two different geometric representations of the same geographical entity at large and small scales as input. Firstly, the corresponding relationship between the coordinate vertices of the two geometric representations is established based on the DTW algorithm, and then the geometric data at any mesoscale is dynamically derived using the linear interpolation method to achieve continuous cartographic generalization. The correctness of the correspondence between vertices directly determines the quality of the linear interpolation results. The geometric representation of the same entity at different scales often has different coordinate points, and the correspondence between vertices is one to many. In order to find the optimal vertex matching, the DTW algorithm is used to solve the optimal matching with the vertex distance as the matching cost and the overall minimum distance as the objective function. Experiment results show that the vertex matching method based on DTW can adapt to different map generalization scenes, and the cartographic generalization effect supported by this method can achieve continuous, smooth and gradual changes, which conforms to the cartographic representation rules and human spatial cognition.

Using the classical CNN network method to construct the automatic extraction model of remote sensing image of Guiyang road elements

SHE Zuoming, SHEN Yongzhi, SONG Jianhong, XIANG Yujin

2023, 0(4):  177-182.  doi:10.13474/j.cnki.11-2246.2023.0126

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Road extraction comprehensively consider the accuracy, computing ability and adaptability to the environment of Guiyang in the interpretation process,so several links in the deep learning neural network model are decomposed. Through multiple rounds of comparative experiments and analysis,a model for automatic extraction of remote sensing images of road elements in Guiyang is established in this paper,the data extracted in batches are analyzed and optimized to complete the filling of some road attributes, which largely realizes the automatic intelligent and efficient extraction of road entities.The practical problems and technical routes involved in the process can provide reference for the natural resources business carried out by the municipal and county level satellite remote sensing application technology departments.