Table of Content

25 September 2023, Volume 0 Issue 9

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Performance analysis of BDS-3 precise point positioning in different periods

CUI Yang, CHEN Zhengsheng, WEI Jiaochen

2023, 0(9):  1-5.  doi:10.13474/j.cnki.11-2246.2023.0255

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Based on the analysis of the change of the number of BDS-3 satellites received by 23 MGEX stations in different periods, the precise point positioning (PPP) of BDS-3 data in different periods is calculated, and the effect of variation in the number of BDS-3 satellites on the accuracy and convergence time of PPP is compared and analyzed.The results show that: ①Compared with DOY 1 in 2021 and 2022, the average number of BDS-3 satellites received by the 23 MGEX stations in the world increased from 6.2 to 11.1.②After the ground station receives more BDS-3 satellites, the static PPP accuracy is increased by 11.4%, and the convergence time is shortened by 18%; The accuracy of simulated dynamic PPP is improved by 28.0%, and the convergence time is reduced by 31.9%.

Performance analysis of precise point positioning of BeiDou-3 Navigation Satellite System

ZHU Xiaowei, YUAN Zhanliang, YANG Yaohuan

2023, 0(9):  6-11,58.  doi:10.13474/j.cnki.11-2246.2023.0256

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BeiDou-3 navigation satellite system (BDS-3) was officially opened on July 31, 2020, providing high-precision positioning, navigation and time service for global users. Based on the dual-frequency undifferenced and uncombined precise point positioning (PPP) model, this paper systematically evaluates and compares the global positioning performance of BDS-3 PPP and GPS PPP from the convergence performance and positioning accuracy. The results show that the convergence performance and positioning accuracy of BDS-3 PPP and GPS PPP in the global scope are basically the same. The convergence time of static PPP in E,N,U direction is 16.8,8.6,19.0 min, and the positioning accuracy is 1.1,0.8,1.8 cm. The convergence time of kinematic PPP in E,N,U direction is 34.9,19.9,49.8 min, and the positioning accuracy is 4.4,3.2,7.8 cm. In the Asia Pacific region, the PPP positioning performance of BDS-2+BDS-3 integrated PPP is obviously better than that of GPS PPP especially in the positioning environment with high satellite cut-off elevations.

Accuracy analysis of two precision ephemeris extrapolation methods for BeiDou satellites

SHEN Shaofei, LEI Weiwei, LI Zhennan, MA Chenyang

2023, 0(9):  12-17,69.  doi:10.13474/j.cnki.11-2246.2023.0257

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The International GNSS Service Center only provides the precision ephemeris data from 00:00:00 to 23:45:00 on the same day. To obtain the complete ephemeris data on the same day, the ephemeris data of 23:45:00—24:00:00 period is often obtained by the method of coordinate extrapolation. In this paper, we use trigonometric interpolation and generalized extended approximation to extrapolate the precise ephemeris orbital coordinates of BeiDou satellites of different types and time intervals for a period of time. The results show that the extrapolation accuracy of the precise ephemeris orbital coordinates of GEO satellites is better than that of IGSO and MEO satellites. The extrapolation accuracy of the two extrapolation methods is significantly higher for the 5 min interval precision ephemeris than for the 15 min interval precision ephemeris, and the extrapolation accuracy of the trigonometric interpolation method is better than that of the generalized extended approximation method with one to two orders of magnitude. Therefore, when extrapolating the orbital coordinates of the precision ephemeris of BeiDou satellites, the trigonometric interpolation method with higher accuracy and the use of ephemeris data with 5 min interval can be preferred for the extrapolation calculation.

Monitoring and analysis of deep foundation pit settlement of underground garage based on BeiDou Navigation Satellite System

HUANG Xin, ZHANG Jiwen, YU Yongtang, XU Chuanzhao, ZHANG Shuai, ZENG Tao, WANG Jingge

2023, 0(9):  18-24.  doi:10.13474/j.cnki.11-2246.2023.0258

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In order to investigate the monitoring accuracy of Beidou deformation monitoring system under construction interference conditions, the BDS deformation monitoring system is applied to an underground garage deep foundation settlement monitoring project in Xi'an, and the settlement monitoring data during the construction period and after the construction period are obtained. According to the wavelet noise reduction principle, the monitoring data are smoothed and noise reduced, and the BDS monitoring data are compared with the level monitoring data for analysis. Finally, the final settlement of the site was predicted. The results show that the construction interference will cause the BDS monitoring data to contain a large amount of noise in a certain wavelength range. However, after the 5-layer decomposition of the original data by Daubechies wavelets, smooth settlement monitoring data can be obtained, and the average relative error of the processed data and the level monitoring data is less than 10.31%. The final settlement at the site was obtained in the range of 100~110 mm based on the noise reduction data using the modified Gompertz function prediction method. The related results can provide a reference for the application of BeiDou positioning system in the ground deformation observation project.

BDS-3 for control surveying application within Africa

LAI Jinfu, SHI Junbo, HU Xuan, TIAN Kun, OUYANG Chenhao

2023, 0(9):  25-29,45.  doi:10.13474/j.cnki.11-2246.2023.0259

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China's BDS-3 satellite navigation system is capable of global positioning service. Investigation of BDS-3 for control surveying will promote BDS-3 applications in countries along the “Belt and Road”. This paper, for the first time, applies BDS-3 to an engineering survey control network in Equatorial Guinea, Africa. The control network adopts the point-connected E-class network observing strategy. Five sessions and 11 control points are designed in this network with average baseline distance of 3.67～6.25 km. The data processing results using domestic receiver, domestic baseline processing software and domestic adjustment software show that: ①the number of observed Beidou-3 satellite is 8～10 in Equatorial Guinea; ②the overall accuracy of BDS-3 is better than GPS in terms of baseline loop misclosure, three-dimensional unconstrained adjustment and two-dimensional plane constraint adjustment; ③two-dimensional plane coordinates obtained by BDS does not exceed 1.09 cm with respect to those of GPS. This paper verifies that BDS-3 has comparable control surveying performance as GPS in Africa, which provides a valuable reference for BDS-3 control surveying application to the globe.

PDR algorithm based on Kalman filter for optimizing heading

ZHU Juntao, LIN Zhiyu, LI Hailin, REN Zhaocai, CHEN Rongsheng, LAN Rongtian, DAI Chengyuan

2023, 0(9):  30-34,63.  doi:10.13474/j.cnki.11-2246.2023.0260

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PDR technology based on the smartphone platform has become a hotspot in indoor positioning research at home and abroad because of its mature technical conditions and ease of realization on a wide scale. However, the accuracy of smartphone sensors is limited, and the geomagnetic information in the indoor environment will be interfered with by the indoor electromagnetic environment, which will affect the positioning accuracy of the PDR algorithm. Therefore, this paper proposes a smartphone heading optimization method based on the Kalman filter, with the smartphone as the research carrier. The theoretical study and field test are conducted by fusing the geomagnetic and gyroscope sensor data of smartphones, and the heading accuracy in the PDR algorithm is optimized. The average error of the optimized positioning improved to 1.36 m.

Analysis of the performance of navigation inter-satellite link system satellite ground time synchronization and its related factors

CHEN Xiaofeng, BAI Yan, GUO Yanming, WANG Rong, PENG Siqi

2023, 0(9):  35-39.  doi:10.13474/j.cnki.11-2246.2023.0261

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It's a better remote high-precision time transfer method that applies the navigation system inter-satellite link to the satellite-ground time synchronization by using the BDS. The satellite-ground time synchronization can offset most of the channel errors through two-way measurement, then improve the measurement accuracy,but there are still some residual errors caused by the inconsistency between upstream and downstream paths,which will diminish the accuracy of time synchronization. This paper introduces the basic principle of time-synchronization,gives the main error correction methods in the process of time-synchronization,focuses on the influence of orbit a priori information on the time-synchronization performance,analyzes and verifies the actual time-synchronization data using different precision orbits.The results show that the RMS values of the residuals of the satellite-ground clock difference fitting solved by using BeiDou broadcast ephemeris and precision ephemeris are better than 0.1 ns,and the time synchronization accuracy can be further improved by smoothing when the orbit data are superimposed with a certain degree of random errors.The research and analysis in this paper can provide some technical reference and accumulation for the realization of high-precision satellite-ground time synchronization.

Spatio-temporal layout optimization of shore-based GPS-R water surface high-retrieval stations

SANG Wengang, WANG Zhaoran, ZHANG Xingguo, JIN Fengxiang

2023, 0(9):  40-45.  doi:10.13474/j.cnki.11-2246.2023.0262

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The accuracy, availability and reliability of shore-based GPS-R retrieval of water surface height are closely related to the azimuth, incident angle, effective arc length and number of visible satellites falling into the specified water area at the station. In order to improve the observation efficiency of inversion points, this paper comprehensively considers various factors such as the first Fresnel zone, the relationship between the station and the orientation of the water system, and the selection of the range of incidence angles for different water system types, then proposes the concept of inversion event and establish the optimization strategy of shore-based GPS-R spatio-temporal layout. The designed simulation experiment and the measured data are verified, and the results show that the both have good consistency. However, due to the existing GPS constellation structure, the distribution of inversion events by users in the northern hemisphere presents the characteristics of “the most in the north, followed by east and west”. Therefore, the optimization strategy based on inversion events can effectively carry out the evaluation and selection of candidate sites in the survey area. At the same time, according to the inversion events, the optimal period of the station and its periodic change law can be further screened, so as to verify that the research on the optimization of the space-time layout of the station can effectively guarantee the high efficiency and quality of the shore-based GPS-R inversion of water surface, and promote the GPS-R technology promotion from theory to application. The full use of GNSS permanent observation stations deployed around large and medium-sized reservoir dams, reservoir bank slopes, and coasts in our country at this stage are important references for the application of GPS-R inversion of water surface height.

Application of RSA-BP combined model in GNSS height fitting

LIU Yintao, REN Chao, WANG Junnan, ZHANG Yan, HE Guanghuan

2023, 0(9):  46-51.  doi:10.13474/j.cnki.11-2246.2023.0263

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Aiming at the problem that the accuracy of constructing GNSS height anomaly fitting model in a complex terrain area is limited, a method based on the reptile search algorithm(RSA) is proposed to optimize the BP neural network. The RSA is used to solve the problems of local extremes and gradient descent of BP neural networks by global optimization of the weights and thresholds of neurons between the layers of traditional BP neural networks. At the same time, the height data of encrypted points above the third class level survey accuracy were selected as the sample set and learned and trained using RSA-BP neural network. Compared with the least squares support vector machine and the multi-surface function fitting performance, the RSA-BP neural network model has the highest fitting accuracy, the best stability and the best fit with the actual height anomalies.

Indoor real-time fusion positioning based on PDR+BLE

XU Hao, WU Xue, LI Chunguang, BEI Jinzhong, CHEN Chong, LI Dehai

2023, 0(9):  52-58.  doi:10.13474/j.cnki.11-2246.2023.0264

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Indoor positioning technology is becoming a hot research topic in the field of ubiquitous navigation and positioning due to the blockage of navigation satellite signals indoors. PDR and BLE positioning are the common positioning means of inertial positioning and RF signal positioning, but PDR positioning is continuous and stable but has accumulated errors, while BLE positioning has no accumulated errors but has poor positioning accuracy. In this paper, PDR/BLE real-time fusion positioning is proposed to meet indoor positioning requirements in complex environments. Firstly, the improved algorithm of BLE proximity correction PDR is proposed for the problem of PDR error accumulation; then the adaptive robust PDR/BLE fusion positioning algorithm based on EKF is proposed for the problem of large coarse difference in BLE positioning.The results show that the BLE proximity correction PDR algorithm improves the localization accuracy by 19% and the EKF-based adaptive robust fusion positioning accuracy by 21% compared with the traditional algorithms, which have significant improvement in both positioning accuracy and stability.It will also have high applicability and scalability in the field of indoor positioning.

Research on the robust positioning model of ORB-SLAM2 in outdoor glare scene

WU Siqi, LIU Fei, BAI Yu, MA Yuntao, WANG Fei, GUO Ziyu

2023, 0(9):  59-63.  doi:10.13474/j.cnki.11-2246.2023.0265

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In order to solve the problem of low stability of visual SLAM in outdoor glare scenes, combined with the method of deep learning in the field of image processing, an improved ORB-SLAM2 algorithm for outdoor scenes containing glare interference is proposed. Firstly, the images taken by the positioning camera are fed into the pre-trained U-Net network for processing, which can effectively remove the glare of the pictures, while maintaining the original information output for the images without glare interference. Secondly, the image brightness judgment algorithm used to judge the brightness of the output images of the network, and the contrast limited histogram equalization is used for the low-brightness images. According to the experimental results in actual outdoor scenes, the motion trajectory of the improved ORB-SLAM2 system is closer to the real motion trajectory of the camera than the original system, and the system has better robustness in outdoor glare scenes.

A similarity approximation algorithm for matching UAV and satellite image

LUO Qingli, ZHANG Shubin, CHEN Xiang, WEI Jujie

2023, 0(9):  64-69.  doi:10.13474/j.cnki.11-2246.2023.0266

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The matching accuracy of the current algorithms is not high enough when UAV and satellite images have a large spatial resolution difference. In order to avoid it, a similarity approximation algorithm for matching UAV and satellite images is proposed. The algorithm applies Gaussian filtering to the UAV images before matching, improves the scale similarity between the UAV image and the satellite image, and finally improves the accuracy of the matching algorithm. Experimental results demonstrate it has high matching accuracy and it is suitable for UAV image matching and autonomous positioning when the spatial resolution difference between UAV image and satellite image is large.

Application and analysis of Sentinel-1 images in Antarctic grounding line extraction

ZHAO Xianren, XING Zhe, ZHANG Feng, GUO Canwen, WANG Jing, SUN Yi, MA Yong, ZHAO Binru, WANG Jian

2023, 0(9):  70-76.  doi:10.13474/j.cnki.11-2246.2023.0267

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The grounding line is the boundary between the inland grounded ice sheet and the floating ice shelf. Precise extraction of the grounding line has a great significance for the calculation of the material balance of Antarctic glaciers, the modeling of glacier dynamics, glacier changes and sea level changes. This paper aims at the application characteristics of Sentinel-1A/B radar image data in the large-scale extraction of Antarctic grounding line. Based on the Sentinel-1A/B radar image data in 2020 and the DDInSAR method, a large-scale extraction of the Antarctic grounding line is carried out.The grounding line is about 23 472 km.Combined with MEaSURE_GL, MOA_ Gl2009,MEaSUREs velocity and other data,we have comprehensive analyzed the grounding line extraction result.The result shows that using Sentinel-1A/B radar image data and DDInSAR method can realize long-term, efficient and comprehensive extraction of Antarctic grounding line.The grounding line in different regions of Antarctica has different changing characteristics, including stability, retreat, advance, disappearance and ice rise.In the Antarctic Peninsula and the West Antarctic, we can use the 6 d Sentinel-1A/B radar image data to extract the grounding line. In the large part of the Eest Antarctic,we can only use the 12 d Sentinel-1A/B radar image data to extract the grounding line.The strength of tidal motion affects the quality of the grounding line extraction, the grounding line extraction quality is higher in the strong tidal area of the West Antarctic, and the grounding line extraction quality in the weak tidal area around the East Antarctic ice sheet is poor or the result is vacant.The extraction of the Antarctic grounding line is greatly affected by the ice velocity, when the ice velocity exceeds 400 m/a, the extraction quality of the grounding line is poor or even unable to extract due to the existence of the large ice velocity.When using Sentinel-1A/B radar image data to extract the Antarctic grounding line, the image data of the Antarctic Peninsula and the East Antarctic are preferentially selected during the autumn period, and the image data of the West Antarctic during the summer period are preferentially selected.

Research and improvement of histogram bimodal method in water body extraction from remote sensing images

WANG Ruyue, ZHOU Hangyu

2023, 0(9):  77-81.  doi:10.13474/j.cnki.11-2246.2023.0268

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Based on multispectral remote sensing data, the advantages of using the water body index method to extract watershed information are obvious and widely used. However, in the process of implementation, the selection of algorithm depends on the specific watershed environment, and most of the current studies adopt specific algorithms based on a given region with poor portability. In this paper, winter and summer data from five regions in eastern China are selected and normalized using the modified normalized water body index (MNDWI) based on the spectral data from Landsat 8/9 satellites, on which the shortcomings of the histogram bimodal threshold method are studied and improved. The experimental results show that the accuracy of the improved histogram bimodal method for extracting waters information is significantly improved, and it no longer depends on a specific waters environment, and its adaptability is significantly improved.

Analysis on the potential habitat and corridor of Trachypithecus francoisi in Jinfomountain,Chongqing city

TAO Peifeng, YUAN Yue, LIU Jian, ZHANG Bin, HE Yanliang, XIAO He

2023, 0(9):  82-86,99.  doi:10.13474/j.cnki.11-2246.2023.0269

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Trachypithecus francoisi, the national first-class protected animal, whose habitat has been destroyed and is in danger due to human activities now. In this study, taking Jinfo mountain, the main distribution area of Trachypithecus francoisiin in Chongqing, as an example, seven environmental impact factors closely related to the habitat are selected from the aspects of topography, vegetation, human activities and drinking water factors, and the habitat suitability of the Trachypithecus francoisito analyzed. The ecological corridor between potential habitats is constructed using the minimum cumulative resistance (MCR) model. The results show that the most suitable habitat area is 178.07 km²,accounting for only 12.15% of the total area of the study area. The Trachypithecus francoisi mainly distributes in the valleys in the middle and northeast of Jinfo mountain. The potential habitat patches are strip-shaped,obviously fragmented, with high altitude, steep slope, proximity to water source,high vegetation coverage and far away from human disturbance. There are 56 ecological corridors constructed,with a minimum width of 303.9 m, a total length of 147.82 km and a total area of 43.89 km². This study has important guiding significance for the protection of the population and habitat of the Trachypithecus francoisi.

Temporal-spatial characteristics of surface velocity of the Gangpu glacier based on OICC-SBAS technology

OU Haifeng, ZI Chengdai, TENG Xingfa, GUAN Shudan

2023, 0(9):  87-92.  doi:10.13474/j.cnki.11-2246.2023.0270

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In this paper, we use Sentinel-2 data to extract and analyze time-series surface motion velocities and spatial-temporal variability characteristics of Gangpu Glacier from 2015 to 2022 using optical imagery cross-correlation technology (OICC) and small baseline subset (SBAS). The results show that there are obvious spatial differences in the surface flow velocity of Gangpu Glacier, and the high values of flow velocity are mainly concentrated in the upstream material accumulation area, which has complex deformation characteristics, with the annual maximum flow velocity of 82.5 m/a. The overall fluctuation of the flow velocity in the main body of the glacier is small, mainly between 40 and 50 m/a. In terms of temporal characteristics, the flow velocity of Gangpu Glacier is relatively stable during the study period, with little difference in flow velocity between years. Meanwhile, the final offset directions obtained using the east-west and north-south offsets are consistent with the actual flow direction of the glacier, and the offset errors in the selected stabilization region only account for 0.04% to 0.7% of the maximum flow velocity of the glacier, which confirms the reliability of the results of the glacier time-series surface flow velocity.

Estimation of building surface solar irradiance based on photogrammetry matching point cloud

DAI Zhisheng, WANG Pengfei, ZHOU Guangjian

2023, 0(9):  93-99.  doi:10.13474/j.cnki.11-2246.2023.0271

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Aiming at the problems that the current solar irradiance evaluation methods of buildings are difficult to take into account both the roof and the facade of the building, and the laser point cloud data cost is high, which is not suitable for obtaining the point cloud of the building surface in a large range and high density. In this paper, an integrated evaluation method for building surface solar irradiance based on dense matching point clouds of slanted images is proposed. The main content of this method is to obtain the 3D building model of the area of interest by using the UAV oblique image, and to simulate the shadow and calculate the solar irradiance of the building surface by combining the shadow simulation algorithm and the simplified solar radiation model. The experimental results show that this method can accurately calculate the solar irradiance of the building surface, which not only expands the application range of tilt photogrammetry, but also provides reliable data support for assisting architects in designing the building surface and maximizing the use of solar energy on the building surface.

Analysis method for bridge structure monitoring data based on Savitzky-Golay smoothing-wavelet noise reduction processing

DONG Shi, LONG Zhiyou, BI Jiefu, WANG Jianwei, SHAO Yongjun, YANG Chao, ZUO Chen, ZHANG Shiyuan, WAN Zhaolong

2023, 0(9):  100-106.  doi:10.13474/j.cnki.11-2246.2023.0272

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Bridge structural health monitoring signal data have some complexities such as burrs, noise and outliers, which produce huge deviations in signal data analysis and assessment of bridge structural status. In this paper, we propose a systematic approach to solve the complex problems in bridge structure monitoring data processing. Firstly, the applicability of each method is evaluated by comparing Savitzky-Golay (SG) filtering and traditional smoothing methods. Secondly, the optimal wavelet basis function and the optimal wavelet decomposition scale are quantified and selected based on the composite evaluation index. Finally, the Kalman filter is used to fuse four strain gage data of the same monitoring project and verified by Monte Carlo simulation. The study shows that the SG smoothing-wavelet noise reduction method is proposed in this paper can provide a more comprehensive and systematic reference for bridge health monitoring data processing.

Quantifying the structural characteristics of Shenzhen road network by POI spatial distribution

GUO Han, MA Ding, YE Aiwen, MA Kenan, ZHU Wei

2023, 0(9):  107-112.  doi:10.13474/j.cnki.11-2246.2023.0273

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Streets as the main infrastructure of a city,not only characterize the urban form,but also works as carriers of human political,economic,cultural and social activities. In the past,the exploration of urban roads mostly focused on the analysis of the relevant factors of geographical geometric space and the surrounded built environment,but seldom studied from topological network perspective. Taking Shenzhen as an example,this paper depicts the network structure characteristics of urban roads through four kinds of centrality indicators,and analyses the complex-network structure and its correlation with the distribution of Shenzhen POI data. The results show that those four structural centrality indicators help to explain the complex characteristics of urban road networks from different angles. Moreover,the degree centrality of road network structure and the eigenvector centrality have higher relevance to the interpretation of POI,but less for the betweenness centrality and closeness centrality. At the urban scale,we also find that expressways are mostly used for transportation but less social activities,so they have a lower correlation. At the street scale,the main roads in each community support the social activities,so both their centrality values and correlations are relatively higher.

Accurcy analysis of GNSS height transformation based on deep BP/ELMAN neural network in the mountains

WEI Dehong, XUAN Jianhao, YANG Jiawei, ZHANG Xingfu, YU Xu

2023, 0(9):  113-116,143.  doi:10.13474/j.cnki.11-2246.2023.0274

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It is of great practical value to transform the GNSS geodetic height into the normal height with higher precision in the mountains. This paper uses the high-precision GNSS leveling data of the GSVS2017 project to analyze the accuracy of GNSS height transformation based on deep BP/ELMAN neural network, general regression neural network (GRNN), radial basis function neural network (RBFNN), support vector machine regression (SVR), quadratic curve fitting and surface fitting, etc. The results show that: ①When the distance between training points is 50, 30, 15, 10 and 5 km, the deep BP/ELMAN neural network with the hidden layer activation function ReLU can obtain higher precision results, and they are more accurate than GRNN, RBFNN, SVR, quadratic curve fitting and surface fitting. ②The deep BP/ELMAN neural network with the hidden layer activation function ReLU are used for GNSS height transformation. Among the five kinds of training point spacing, more than 90% of the height difference can meet the fourth-order leveling accuracy, and more than 75% of height difference can meet the third-order leveling accuracy; when the distance between training points spacing is 5 km, more than 55% of the height difference can meet the second-order leveling accuracy.

Remote sensing inversion and regularity analysis of suspended sediment in Pearl River Estuary based on machine learning model

YANG Chuanxun, LI Yong, YANG Ji, SHU Sijing

2023, 0(9):  117-123.  doi:10.13474/j.cnki.11-2246.2023.0275

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Based on the water quality sampling data and hyperspectral data of suspended sediment in the Pearl River Estuary, this paper constructs artificial neural network (ANN), support vector regression machine (SVR) and random forest (RF) suspended sediment inversion models. The results show that the prediction accuracy of the models is RF,ANN,SVR, and the random forest model has the best fitting effect. The random forest model is used to invert the suspended sediment concentration in the Pearl River estuary. The results show that the suspended sediment concentration at the Pearl River port is high in the west and low in the east, and it gradually decreases from the nearshore to the offshore. It is mainly due to the trumpet-shaped topography of the Pearl River estuary. Under the combined action of monsoon and tide, the top area of the Pearl River estuary is strongly mixed by tide and wind direction. In the area far away from the top of the Pearl River estuary, the terrain is relatively open, and the suspended sediment of each tributary runoff is concentrated and accumulated in the southwest region of the Pearl River estuary, resulting in a high suspended sediment concentration in the southwest region of the Pearl River estuary.

Monitoring of flood channel bank collapse in the southern section of the Jingjiang River based on high-resolution remote sensing images: taking the Dengpanzhou bend as an example

HE Qiuhua, ZOU Juan, YU Shuchen, YU Deqing, TANG Hui, MEI Jinhua, LUO Jianqiang, ZHAO Dong, ZOU Cong

2023, 0(9):  124-128.  doi:10.13474/j.cnki.11-2246.2023.0276

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To study the situation of bank collapse in the Yangtze River tributary, high-resolution remote sensing image data and a quantitative description method was used to analyze the Songzi River in the southern part of the Jingjiang River section,Taking Dengpanzhou Bend and Jiangxinzhou as examples, monitoring the bank collapse situation from 2013 to 2022. Monitoring shows that there are varying degrees of bank collapses in both the river channel and the Jiangxinzhou. The width of the southern river channel at the monitoring point increased from 203.11 meters in April 2013 to 287.94 meters in November 2022,with an average annual expansion of 8.5 meters and a monthly expansion of 0.74 meters. During the monitoring period, all five monitoring points experienced varying degrees of bank collapse. The distance from the most severe monitoring point to the riverbank decreased from 122.56 meters in April 2013 to 60.13 meters in November 2022. The results indicate that using high-resolution remote sensing images for monitoring bank collapse is a very effective monitoring method and a beneficial supplement to conventional monitoring; It is recommended to strengthen the monitoring and protection of riverbank collapses in the Yangtze River tributaries while carrying out monitoring and construction of protection projects for the main stream of the Yangtze River.

Dynamic monitoring of new remote sensing technology for railway safety

DU Yuzhu

2023, 0(9):  129-134.  doi:10.13474/j.cnki.11-2246.2023.0277

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The external safety environment of railways has become one of the main risks affecting railway operation safety. Conducting dynamic monitoring of railway environmental safety can effectively address the aforementioned risks, and is of great significance for preventing potential emergencies and ensuring safe railway operation. In order to improve the effectiveness of dynamic monitoring methods for railway environmental safety, the author conducte research on dynamic monitoring of railway environmental safety based on new remote sensing technologies. Firstly, the external safety environment of the railway is analyzed. Then the characteristics of various remote sensing monitoring technologies and the advantages and disadvantages of their application in dynamic monitoring of railway environmental safety are compared. Finally, the monitoring and evaluation of geological disasters along the railway, monitoring of railway land occupation, and a dynamic monitoring plan has been designed for typical hidden dangers such as illegal mining on overlying railways, and experimental testing has been conducted. Special issues that arise during the testing period have been specifically addressed. The experimental results indicate that the combination of multiple technologies and complementary advantages can achieve dynamic monitoring of railway environmental safety, effectively improve the level of railway safety and environmental management, and provide certain technical support for railway environmental disaster prevention and emergency response.

Terrain-level geographic scene data production based on WorldView-3 satellite strip image

LIU Dongzhi, REN Yi, ZHU Wanxiong

2023, 0(9):  135-138.  doi:10.13474/j.cnki.11-2246.2023.0278

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3D real China construction requires the local level to produce terrain-level geographic scene data including 2 m grid DSM, DEM and better than 0.5 m resolution DOM. For the WorldView-3 satellite strip image data, the traditional gray level matching, feature matching and transform domain matching methods can not obtain enough connection points to meet the requirements. The probability relaxation control point matching method based on frequency phase matching is used to match the connection points, and the number of connection points meeting the accuracy requirements is large and evenly distributed. The accuracy of the terrain-level geographic scene data of DSM, DEM and DOM produced subsequently meets the requirements, which provides technical support for the smooth implementation of the 3D real Tibet Chayu pilot construction.

Application of 4D labelling in intelligent driving BEV perception

ZHANG Panpan, SONG Jiashun

2023, 0(9):  139-143.  doi:10.13474/j.cnki.11-2246.2023.0279

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Perception is an important part of intelligent driving application. With the advancement of BEV(bird's-eye view) perception algorithm in the industry, higher requirements are put forward for the quality and order of magnitude of data annotation. In this paper, the detailed requirements of BEV perception algorithm for data annotation are deeply studied, and a new 4D data annotation method upon vector space is proposed based on the weakness of current mainstream data annotation methods. The annotation results are projected into the image space in real time, and the output of massive training samples can be truly annotated once. Practical results show that 4D annotation can not only improve the annotation efficiency more than a hundred times, but also guarantee the quality of data annotation in essence and meet the needs of BEV perception.

Construction and application of remote sensing interpretation sample database for surface elements

ZHANG Baoan, GAO Xiaolong, JIN Zaiyan, MA Lanhua

2023, 0(9):  144-149.  doi:10.13474/j.cnki.11-2246.2023.0280

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In the face of the construction of natural resource remote sensing monitoring system and the annual update demand for key elements of provincial basic surveying and mapping,a method for constructing a provincial remote sensing interpretation sample database is proposed based on geographical and national surface coverage as the main reference data. Firstly,a sample classification system for remote sensing interpretation of natural resources in Gansu province suitable for deep learning and sample selection standards that take into account geoscience knowledge are developed. Based on this,three types of sample datasets including full element,single element,and change detection are constructed,including different scale units. Then,based on the self-developed Gansu province remote sensing interpretation sample library platform,a full link technical system from sample collection,model training,intelligent interpretation to quality assessment is constructed. The experimental results show that for different scale regions,the accuracy of feature extraction reaches 90%,and the accuracy of change detection reaches 74%,achieving adaptive interpretation of surface elements from coarse to fine granularity. The research results have been applied in the provincial basic surveying and mapping update,urban land space monitoring,non-agricultural monitoring and other fields in Gansu province,improving the accuracy and intelligence of natural resource management.

A method for identifying abnormal settlement data of high-speed railways using deformation rate considering sensitivity

LIANG Ce, HUANG Yuanku, LIU Junfei, WANG Wanqi, ZHU Jun

2023, 0(9):  150-154.  doi:10.13474/j.cnki.11-2246.2023.0281

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For the massive data of settlement observation of high-speed railway under construction, in order to quickly, batch and automatically identify abnormal data that can not reflect the real settlement state, based on the historical big data of settlement observation and mathematical statistics methods, the reference threshold for identifying abnormal settlement data of subgrade, bridge and culvert, and tunnel under each main working condition is formulated. After removing invalid observation data, a strategy of prioritizing sensitivity and assisting in verifying stability with calculation results is adopted to compare the fluctuation of average deformation rate with the reference threshold, achieving automatic identification of abnormal settlement data. Using these methods, the railway settlement deformation observation information system is designed and developed and popularized in the Xi'an-Ankang and Xi'an-Yan'an high-speed railway projects. Empirical calculation shows that between the single deformation rate and the average deformation rate, the method's misjudgment rate can be suppressed and the stability can be improved by setting sensitivity adjustment coefficient. In the project, it is possible to quickly identify abnormal settlement data and the location of the mileage.

Analysis on safety monitoring and controlling of intelligent vehicle basic map

WU Jiatong, HUANG Long, WANG Yong, LUO An

2023, 0(9):  155-159,170.  doi:10.13474/j.cnki.11-2246.2023.0282

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Intelligent vehicle as the strategic direction of the development of the automotive industry, coupled with the growing maturity of autonomous driving technology, the basic map carried on the vehicle has become a new product in the map industry. The real-time mapping, dynamic update, information interaction, data crowd source and other behaviors accompanying the great development of basic maps pose severe challenges to geographic information security, which is a problem that cannot be ignored in national geographic information security. This paper comprehensively combs the concept, characteristics and application of intelligent vehicle basic map under different automatic driving levels. The current research status and future development direction of basic map related standards at home and abroad are systematically analyzed. This paper summarizes the information technology risk points and current prevention and control difficulties in the application of basic map, and puts forward some suggestions.

Exploration and practice of urban spatial stereo unit in the construction of CIM platform

TIAN Linan, SUN Qi, XU Wenkun, DONG Ping, TIAN Zhixin, RONG Chao, JI Zezhong

2023, 0(9):  160-164.  doi:10.13474/j.cnki.11-2246.2023.0283

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The construction of CIM basic platform has brought together a large amount of spatiotemporal and non spatiotemporal data in cities, providing rich data sources for smart cities. At the same time, the integration and use of data has also encountered new challenges. This article focuses on the problems of multi-source data fusion in CIM platform construction, and put up with key technology of spatial 3D grid and CIM data fusion using the geospatial grid encoding rules, knowledge graph, and multi-source semantic model. On the basis of CIM1-7 products, the concept of urban spatial 3D grid is proposed. By building multi-level three-dimensional spatial 3D grid, it can realize information fusion of mass urban base and multiple elements based on urban space, and provide more convenient and safer urban information services for various business applications.

Design and practice of core curriculum system for top undergraduate major in geographic information science

KANG Mengjun, REN Fu, SU Shiliang, WANG Mingjun, YING Shen

2023, 0(9):  165-170.  doi:10.13474/j.cnki.11-2246.2023.0284

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With the development of geography, surveying and mapping science and technology, information technology and other disciplines, the core curriculum system of geographic information science (GIS) is facing the need of revision and improvement. How to design a course system suitable for this major, and what factors need to be referred to, are issues that need to be discussed urgently. Based on the comparative analysis of the GIS major core curriculum system of Peking University, Nanjing University and Beijing Normal University, this paper discusses the design principles and practice process of the GIS major core curriculum system of Wuhan University in detail, and puts forward several factors affecting the curriculum system design, including academic support, social needs, teacher structure, etc., which can provide useful reference for the design of GIS major curriculum system of other universities.

Flexible observation selection of precise BDS real-time kinematic positioning

YE Yuanbin, HOU Xue, ZHANG Xianzhi, ZHANG Yongfeng

2023, 0(9):  171-175.  doi:10.13474/j.cnki.11-2246.2023.0285

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Conventional processing method of BDS precise kinematic positioning is usually based on the experience threshold of baseline length to determine to use the raw or the ionospheric-free (IF) combination observation. However, the ionospheric delay is different at different regions and different time, it is difficult to obtain the optimal solution with the fixed threshold of baseline length, especially in kinematic positioning with the continuously change of baseline length. In this paper, we presented a new method that is flexible observation selection (FOS) for BDS real-time positioning for baselines with a variable lengths. The FOS method is based on the noise of different observations of the receiver and the size of the double-difference ionospheric residuals, and determining the optimal observation of baseline solution by the relationship of the ionospheric delay residual and the measurement noise. When the ionospheric residual is greater than the observed noise of the IF observation, the results of the IF method are better than those of the raw B1 observations, otherwise the results of the B1 observations are better. The results in the static test show that the positioning performance of the FOS method in E, N, and U directions are improved by about 9.6%, 7.5% and 11.4% with respect to the B1 method, respectively, while compared with the IF method are 8.6%, 9.9% and 12.2%. The positioning bias in kinematic test of the FOS method compared with B1 and IF methods are improved by about 11.1%, 13.7%, 17.0%, and 8.3%, 10.7% and 13.8%, respectively, and the ambiguity resolution (AR) rate are increased by 16.9% and 10.2%.

Application and analysis of intelligent bordercontrol based on BeiDou timing technology

FANG Guosheng, QIU Zuxiong, MA Guangxin, YANG Tianran

2023, 0(9):  176-181.  doi:10.13474/j.cnki.11-2246.2023.0286

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With the development of the construction of intelligent border control system, application terminals and servers put forward higher requirements for the accuracy and security of time synchronization. On the basis of analyzing the status and problems of server timing, the paper discusses in depth the demand of intelligent border control system for time synchronization and the selection of key technologies, and proposes the solution and application examples of enhanced network timing and time closed-loop management based on BeiDou Navigation Satellite System. It aims to provide unified time baseline and closed-loop time management for all application terminals and servers of smart border control system, and comprehensively empower business applications of border control system.