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2021 Vol. 46, No. 1

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Reflection plane parameters estimation with GNSS multipath signal

SHAO Yilun, ZHAO Juan, LIU Chengyu, WANG Yan, CHEN Xin

2021, 46(1): 1-6. doi: 10.12265/j.gnss.2020111601

[Abstract](589) [FullText HTML] (359) [PDF 1013KB](53)

Abstract:
GNSS multipath signals widely exist in complex navigation and positioning scenarios such as urban canyons. Although the multipath signal interferes GNSS receiver and reduces positioning accuracy, it provides environment information around the receiver. Based on the coupled amplitude delay locked loops algorithm (CADLL) which senses GNSS multipath signals and extracts feature parameters, a particle filter-based reflection plane parameters estimation algorithm is designed and implemented. The algorithm can enhance the receiver's environment perception in the GNSS multipath environment, the corresponding information can be applied to the fields of scene perception, collision avoidance, path planning and positioning augmentation. GNSS multipath signal recording and algorithm testing are carried out in a static environment. The experimental results show that the algorithm can effectively estimate the position parameters of the reflecting plane. The root mean square error (RMSE) of the azimuth angle of the reflection plane is less than 10 degrees, the RMSE of the elevation angle is less than 5 degrees, and the RMSE of the distance is less than 10 meters.

Relaxation barycentre iterative algorithm for solving parameter estimation of overdetermined distance locating equations

YUAN Xingming, SUN Zhen

2021, 46(1): 7-12. doi: 10.12265/j.gnss.2020052504

[Abstract](408) [FullText HTML] (292) [PDF 723KB](17)

Abstract:
Based on the minimal residual criterion, a relaxtion method is proposed to improve the convergence efficiency of the barycentre method for solving the distance equations. The relaxation factor for adaptive selecting the iterative step of barycentre method is derived by the minimum residual criterion. The proposed method has the advantages of simple iterative format without the matrix inversion and to simplify the procedure without calculating the Hessian matrix. Finally, the novel method is performed to solve the data of GNSS and marine positioning examples to show its performance, and results show the numerical convergence experiments are performed to show the convergence efficiency improvment.

Fingerprint positioning method of CSI based on PCA-SMO

MENG Junjian, ZOU Jingui, ZHAO Yinzhi

2021, 46(1): 13-19. doi: 10.12265/j.gnss.2020111301

[Abstract](671) [FullText HTML] (410) [PDF 1256KB](42)

Abstract:
Wi-Fi channel state information (CSI) contains rich feature information, which enables CSI based fingerprint positioning methods to build higher-dimensional features to improve positioning accuracy. However, the redundant information in the fingerprint features also makes the built-up fingerprint database large in storage, and increasing of the time cost of establishing the positioning model becomes large, and the real-time positioning calculation. In this regard, this paper proposes to use principal component analysis (PCA) method to reduce the dimensionality of the original fingerprint features, and then use the sequential minimal optimization (SMO) algorithm to establish the regression model of the reduced feature and the corresponding position and predict the position. The experimental results show that the algorithm in this paper can effectively overcome the above problems, while the average positioning error is 1.25 m, and the cumulative probability of positioning error within 2 m can reach 97%.

Unmanned aerial vehicle realistic 3D modeling accuracy analysis considering control point uniformity

CHENG Libo, LI Jia, DUAN Ping, WANG Yunchuan

2021, 46(1): 20-27. doi: 10.12265/j.gnss.2020102801

[Abstract](574) [FullText HTML] (287) [PDF 1487KB](28)

Abstract:
Unmanned aerial vehicle (UAV) tilt-photography technology has become the mainstream of the construction of three-dimensional real-field models with its advantages of low cost, high efficiency and high precision. The accuracy of the real 3D model is affected by many factors. This study is mainly focused on the point of view of the uniformity of the control point distribution, to explore its impact on the accuracy of the real 3D model, and propose a more general measure of control point uniformity. Two experiments with different numbers of control points are designed, and each experiment contains three different uniformity distribution schemes. Aerial images of the experimental area were obtained by UAV, and six schemes were adopted to participate in model. By analyzing the model accuracy, the results show that: the accuracy of the real 3D model is poorer when the uniformity of the control points is lower, and the elevation accuracy is worse than the plane accuracy. Increasing the uniformity of the control points will improve the overall accuracy of the model. The improvement of the uniformity of the control points will improve the accuracy of the model at a lower uniformity; the uniformity of the control points can improve the accuracy of the model at a lower uniformity. The uniformity of the control points can improve the accuracy of the model at a lower uniformity. The uniformity of the control points can improve the accuracy of the real 3D model at a lower uniformity. The uniformity of the control points can be used as an evaluation indicator in the deployment of field control points.

GPS positioning algorithm based on Kalman filter and improved DBSCAN clustering combination

GE Qian, HOU Shouming, ZHAO Wentao

2021, 46(1): 28-35. doi: 10.12265/j.gnss.2020100904

[Abstract](1106) [FullText HTML] (175) [PDF 1093KB](70)

Abstract:
Real-time acquisition of geographic location information of smart mobile terminals is the key to the realization of an augmented reality (AR) real-scene smart navigation system. In order to improve the accuracy of GPS positioning for smart terminals, a GPS combined positioning optimization method based on Kalman filtering and improved DBSCAN clustering algorithm is proposed. Kalman filtering is performed on the position coordinate data collected by the GPS system to remove large data fluctuations and control the positioning error range. Using DBSCAN clustering algorithm for classification denoising and secondary clustering, the arithmetic mean value of the data in the class and the total number of data between the classes are weighted to find the center of gravity, and the position coordinates are determined. The experimental results show that the proposed algorithm can effectively improve the GPS single-point positioning accuracy, reduce positioning errors, and at the same time well meet the real-time and robustness requirements of the AR real-world intelligent navigation system.

Visual inertial positioning method based on tight coupling

LU Jiawei, XU Zhe

2021, 46(1): 36-42. doi: 10.12265/j.gnss.2020082801

[Abstract](617) [FullText HTML] (283) [PDF 1373KB](42)

Abstract:
The inertial measurement unit (IMU) is disturbed by its own temperature, bias, vibration and other factors, so the pose is easy to diverge when integrating, and the monocular vision positioning accuracy is poor when the robot moves rapidly. Therefore, this paper studies a visual inertial synchronous simultaneous localization and mapping (SLAM) method based on tight coupling. Firstly, the location problem of visualodometry (VO) is studied. In order to reduce the mismatching of feature points, the feature points extraction method based on Oriented FAST and Rotated BRIEF (ORB) is adopted. Then the mathematical model of IMU is constructed, and the discrete integral of the motion model is obtained by using the median method. Finally, the pose of monocular vision is aligned with IMU trajectory, and the optimal state estimation of robot motion is obtained by nonlinear optimization based on sliding window. The two experiments were verified by constructing the simulation scene ard comparing with the monocular ORB-SLAM algorithm. The results show that the proposed method is better than visual odometer alone, and the positioning accuracy is controlled at about 0.4 m, which is 30% higher than the traditional tracking model.

Coordinate time series analysis of CMONOC stations in Gansu Province considering the influence of colored noise

LIU Shuangtong, XU Jianmin, GAO Zhiyu, CHEN Chen, YANG Shuwen

2021, 46(1): 43-49. doi: 10.12265/j.gnss.2020101002

[Abstract](496) [FullText HTML] (226) [PDF 1487KB](27)

Abstract:
According to the coordinate time series results of 19 CMONOC reference stations in Gansu Province, the maximum likelihood estimate (MLE) was used to explore the optimal noise model of each reference station, the velocity field of the reference station was determined, and the crustal movement in Gansu Province was analyzed. The research results show that the noise characteristics of each coordinate component of the CMONOC reference station in Gansu Province are quite different. "WN+FN" is the optimal noise model, which can better describe the noise characteristics of the three components of the reference station coordinate time series, and The estimated rate uncertainty is 4 to 15 times when only white noise is considered. The average rate of horizontal movement of the CMONOC reference station in Gansu Province under the framework of ITRF14 is 34.54 mm/a and the direction of movement is SEE 98.07°; the average rate of horizontal movement relative to the Eurasian plate is 6.49 mm/a and the direction of movement is NEE 79.23‬°.

Effects of narrowband and pulse interference on the carrier-to-noise ratio of satellite navigation signals

GUO Haiyu, LU Zukun, CHEN Feiqiang, LIU Xiaohui, ZHUANG Zhaowen

2021, 46(1): 50-56. doi: 10.12265/j.gnss.2020100901

[Abstract](1048) [FullText HTML] (309) [PDF 962KB](102)

Abstract:
With the increasing complexity of modern electromagnetic environment, navigation receiver is at higher risk of various interference. Narrowband interference and pulse interference are common means of suppressing interference on satellite navigation signals. Different interference signals have different time-frequency domain characteristics, and their influence on satellite navigation signals is also very different, which is mainly reflected in the carrier-to-noise ratio and bit error rate. In view of the lack of research on pulse interference performance in China, a formula of anti-interference quality factor suitable for pulse interference is proposed by comparing narrowband interference performance evaluation method. This paper deduces the method of calculating the equivalent carrier-to-noise ratio in time domain under pulse interference, and verifies the result through simulation. The result shows that the calculation error of equivalent carrier-to-noise ratio under pulse interference with different duty ratio is less than 0.5 dB, and the result is quite accurate.

Accuracy analysis of single-point positioning in pseudo-range combined with BDS-3 new frequency and Galileo single frequency

PENG Jinsong

2021, 46(1): 57-61. doi: 10.12265/j.gnss.2020102001

[Abstract](760) [FullText HTML] (270) [PDF 747KB](29)

Abstract:
In order to compare and analyze BDS-3/Galileo compatible frequency pseudorange single-point positioning accuracy, based on the measured data of MGEX distributed tracking stations, singal point positioning accuracy of pseudorange combination of dual-system compatible frequencies and non-compatible frequenry of BDS-3 and Galileo are analyzed, together with that of single frequency of BDS-3 and Galileo respectively. It is found through research that BDS-3/Galileo combination effectively improves the visible number of satellites and the geometric structure of satellite spatial distribution compared to a single system. In terms of single system positioning, the single point positioning accuracy of B1C and B2a pseudorange of BDS-3 is better than that of comesponding compatible frequenry of Galileo. In terms of dual-system positioning, the single point positioning accuracy of compatible frequenry pseudorange combination of BDS-3/Galileo is better than that of non-compatible frequenry combination. and the dual-system combination positioning improves the Galileo single-system positioning accuracy better BDS-3, which indicates that the design of BDS-3 compatible frequency effectively improves the compatibility with Galileo system.

New method for helmert transformation without direct conversion parameters and precision analysis

JIANG Yingming, JI Xiaoyu, HOU Xiaowei, FENG Yantong

2021, 46(1): 62-67, 88. doi: 10.12265/j.gnss.2020102002

[Abstract](777) [FullText HTML] (332) [PDF 880KB](24)

Abstract:
For two coordinate reference frames which have no direct conversion parameters, a new method is developed to solve the complex and inefficient problem of traditional multi-step "transition" transformation. This paper takes the coordinates and velocities of 714 stations released by EUREF as an example to convert them from the ETRF2014 to the ETRF2000. The results show that, the coordinate and velocity difference between the traditional method and the method proposed in this paper is in the order of $ {10}^{-8} $ meters and $ {10}^{-9} $ meters per year, respectively. The analysis results verify the feasibility of the calculation method.

Data quality and SPP positioning performance analysis of BDS-3

TAN Liqing, CAO Yang, PENG Qi, TANG Shuai, LIU Jun, YANG Xin

2021, 46(1): 68-76. doi: 10.12265/j.gnss.2020102802

[Abstract](688) [FullText HTML] (558) [PDF 1675KB](57)

Abstract:
The construction of BDS-3 has been completed. At this time, it is very meaningful and necessary to carry out the study and analysis of BDS-3 data quality and positioning performance. Observation data of MGEX stations were used to assess the observation data quality and pseudorange single-point positioning accuracy of BDS-3. Meanwhile, the positioning accuracy of BDS-2 and GPS were compared with BDS-3. The results show that the data integrity rate of BDS-3 at each station is above 95%. The average signal-to-noise ratio of each frequency band is higher than 45 dB·Hz, but signal-to-noise ratio of GEO satellite fluctuates frequently. The average value multipath error of various types of BDS-3 satellites are all less than 35 cm, and the pseudorange noise of most BDS-3 satellites is generally less than 0.3 m. Compared with BDS-2 and BDS-3, the positioning accuracy of BDS-2/BDS-3 has been improved to different extents, but the improvement of BDS-3 positioning accuracy in high latitude areas is very small. BDS-3 can obtain a positioning accuracy better than 3 m and 4 m in horizontal and vertical directions in all regions of the world, which is roughly comparable to GPS positioning performance.

Data analysis of laser line patrol based on different GNSS enhancement systems

WU Tao, ZHANG Xingwei, WANG Hongxing, HUANG Zheng, SONG Yu, LIANG Sen

2021, 46(1): 77-82. doi: 10.12265/j.gnss.2020111902

[Abstract](476) [FullText HTML] (283) [PDF 927KB](30)

Abstract:
The unmanned helicopter equipped with LiDAR for transmission line inspection has the advantages of high accuracy and low cost. In order to obtain high-precision three-dimensional point cloud high-precision geospatial coordinates of high-precision transmission lines, it adopts three different positioning service methods, including base station differential post processed kinematic (PPK), Jiangsu Province CORS (JS-CORS), Qianxun location (QX-CORS), etc. to inspect transmission line inspections, and analyze of the point positioning accuracy and point cloud quality obtained under the three types of positioning. The actual results show that the average error between the plane check point and the elevation check point of the base station differential post-processing positioning method is within 0.1 m, which has the highest accuracy and the best data quality. The accuracy of the JS-CORS real-time positioning method and the Qianxun real-time positioning method are second. It provides a reference for unmanned helicopter carrying LiDAR for power transmission line inspection and selection of positioning methods.

Coordinate time sequence period and noise analysis of Shandong CORS

XI Huan, QU Guoqing

2021, 46(1): 83-88. doi: 10.12265/j.gnss.2020120902

[Abstract](641) [FullText HTML] (175) [PDF 726KB](37)

Abstract:
In view of the difference of period and noise characteristics in different regions, this paper takes the coordinate time series of 27 CORS in Shandong Province from 2015 to 2018 as the research object, and analyzed the period and noise of coordinate components of each station on the basis of data preprocessing. The results show that, there is no strict whole periodic signal in coordinate time series, and the periodic motion in U direction is relatively regular. The spectrum index of coordinate component shows that the noise model of most stations is white noise (WN) + flicker noise (FN). Using the maximum likelihood estimation criterion, the best noise model of coordinate time series in Shandong CORS station is WN + FN, and the best noise model in E and U direction is WN + FN. The best noise model is WN + FN + random walk noise (RWN).

Preliminary analysis of atmospheric water vapor detection performance based on BDS-3

GUO Qiuying, HOU Jianhui, LIU Chuanyou, XU Mingze, SUN Yingjun

2021, 46(1): 89-97, 111. doi: 10.12265/j.gnss.2020090802

[Abstract](403) [FullText HTML] (401) [PDF 1305KB](34)

Abstract:
The preliminary analysis of the atmospheric water vapor detection performance of Beidou-3 global satellite navigation system (BDS-3), which has just been deployed in China, can make better use of the meteorological detection potential of BDS-3. In this paper several methods are compared using data from diffent stations around the world. The results are representative and convincing. The results of the study showed, comparing BDS-3/PWV with GPS/PWV, the average deviation (BIAS) was preferable to 1.0 mm, the root mean square error (RMSE) was better than 2.0 mm, and the correlation coefficients were all above 94%; The mean of the absolute values of the difference between of BDS-3/PWV and GPS/PWV (MEAN) was 1.1 mm, which was 71% lower than BDS-2; The RMSE of BDS-3/PWV and GPS/PWV was 1.4 mm, which was 63% lower than BDS-2. Comparing BDS-3/PWV with ERA5/PWV, BIAS was preferable to 2.9 mm, RMSE was better than 2.8 mm, and the correlation coefficient was above 92%. The MEAN of BDS-3/PWV and ERA5/PWV was 2.1 mm, which was better than BDS-2 reduced by 48%; The RMSE of BDS-3/PWV and ERA5/PWV was 1.6 mm, which was 57% lower than BDS-2. The water vapor detection performance of BDS-3 was much better than BDS-2, which was in good agreement with GPS and ERA5 water vapor detection results.

A street view image change detection method combining semantic segmentation model and graph cuts

LI Wenguo, HUANG Liang, ZUO Xiaoqing, WANG Yizhu

2021, 46(1): 98-104. doi: 10.12265/j.gnss.2020110401

[Abstract](654) [FullText HTML] (356) [PDF 1362KB](30)

Abstract:
Due to the problems of the diversity of the scale, the unclear boundary and the complex spectral information of the ground objects, the performance of the statistical method and machine learning method for the change detection of the high complexity street view images is poor. Therefore, a street view images change detection method combining semantic segmentation model and graph cuts (GC) is proposed in this paper. Firstly, the DeeplabV3+ semantic segmentation model combined with migration learning is used to pre-train the Camvid data set to obtain the pre-trained model in this method; Then a small number of annotated samples from the data set of this paper were used to Fine Tune the pre-training model, which was respectively used for semantic segmentation of street view images in two periods. Then GC method is used to remove the sky, roads,vegetation and other factors, which is impacting on the street view. Finally, change vector analysis (CVA) is used to obtain the difference images, and binarization and accuracy evaluation were carried out for the difference images. The results show that the overall accuracy of the proposed method is better than the Otsu method (OTSU), K-means method, Segnet network migration learning method and DeeplabV3+ network migration learning method, it is a feasible method for detecting changes in street view images.

Ocean current machine shore-based communication based on BDS short message service

WANG Yongding, CHEN Xiaofeng

2021, 46(1): 105-111. doi: 10.12265/j.gnss.2020102005

[Abstract](481) [FullText HTML] (301) [PDF 996KB](37)

Abstract:
In order to solve the problems of working condition monitoring of the ocean current machine and the difficulty of long-distance communication and data transmission between the ocean current machine and the shore, the BeiDou Navigation Satellite System (BDS) was chosen to be applied to the ocean current machine's positioning and communication in the sea. The characteristics of ocean currents and several common operating conditions of ocean current machines are analyzed. The positioning principle of ocean current machine based on BDS-RNSS and the short message communication characteristics of BDS are introduced. “Bit Splicing-LZW” double data compression is applied in the short message communication system. A main control system suitable for ocean current machine communication and draft a communication plan between ocean current machine and shore user terminal is designed, aiming to improve communication efficiency and increase data transmission volume.

Design of environment monitoring and assessment system for natural gas hydrate exploitation based on BDS

CAO Yu, FANG Huiling, ZHAO Yongqi, CUI Haipeng

2021, 46(1): 112-118. doi: 10.12265/j.gnss.2020110601

[Abstract](530) [FullText HTML] (252) [PDF 1682KB](29)

Abstract:
Natural Gas Hydrate (NGH) development technology has become the frontier of scientific and technological innovation in the world. In the development of NGH resources, both safety development and environmental protection should be paid equal attention, in order to accelerate the commercialization of NGH production in the seabed, it is urgent to strengthen the long-term environment monitoring of seabed exploitation. This paper designs an environment monitoring and assessment system for NGH exploitation based on BeiDou Navigation Satellite System (BDS). By displaying the atmosphere, sea water, seabed and underground well of 'four in one' 3D visualization marine stereoscopic space scene, we can obtain the real-time data acquisition and remote transmission of NGH exploitation environment sensors, and realize the real-time safety analysis, tracking and warning function of exploitation environment in the seabed.