Table of Content

20 April 2021, Volume 50 Issue 4

Previous Issue    Next Issue

BeiDou Navigation Satellite System

BDS-3 performance assessment:PNT, SBAS, PPP, SMC and SAR

CAI Hongliang, MENG Yinan, GENG Changjiang, GAO Weiguang, ZHANG Tianqiao, LI Gang, SHAO Bo, XIN Jie, LU Hongyang, MAO Yue, YUAN Haibo, LIU Cheng, HU Xiaogong, LOU Yidong

2021, 50(4):  427-435.  doi:10.11947/j.AGCS.2021.20200549

Asbtract ( )   HTML ( )   PDF (1082KB) ( )  

References | Related Articles | Metrics

With algorithm and methods provided, performance of BDS-3 services including PNT (positioning, navigation and timing), SBAS (satellite-based augmentation system), PPP (precise point positioning), SMC (short message communication) and SAR (search and rescue) is evaluated using different measurement data. Results show that signal in space(SIS) accuracy is 0.23 m(RMS), SIS availability is 99.44%, SIS continuity is 99.99%, PDOP availability is 100%, positioning accuracy is 1.3 m in horizontal and 2.09 m in vertical direction, positioning availability is 99.93% and timing accuracy is 14.7 ns(95%) for PNT service. For SBAS, positioning accuracy in horizontal direction is 1.03 m and in vertical direction is 2.60 m (95%), APV-I availability is 100%. For PPP service, positioning accuracy is 0.17 m(95%) in horizontal direction and 0.22 m(95%) in vertical direction, the average convergence time is 9 min. For regional short message communication, the communication success rate is 99.6%, the communication capacity is 15.3 million times per hour(uplink), 9.35 million times per hour(downlink); while for global short message communication, communication success rate is 96.46%, communication capacity is 0.4 million times per hour (uplink), 0.21 million times per hour (downlink). For search and rescue service, the receiving success rate is 98.3%(with sending power 37 dBm).

Research on performance of BeiDou global broadcast ionospheric delay correction model (BDGIM) of BDS-3

YUAN Yunbin, LI Min, HUO Xingliang, LI Zishen, WANG Ningbo

2021, 50(4):  436-447.  doi:10.11947/j.AGCS.2021.20200421

Asbtract ( )   HTML ( )   PDF (1460KB) ( )  

References | Related Articles | Metrics

On June 23, 2020, the last BDS-3 satellite was launched, which means that the China BDS finished its global system construction. The BDS-3 adopts a new generation global broadcast ionospheric delay correction model (BDGIM) for the single frequency ionospheric delay correction. This paper describes the performance of BDGIM during the period before and after the establishment of the BDS-3 system, in terms of the accuracy of ionospheric delay correction, BDS single-frequency pseudorange positioning and the broadcast model coefficients. To access the performance of BDGIM, the high-precision global ionospheric map (GIM) and the measured ionospheric electron content (TEC) data are selected as references. The accuracy of GPS Klobuchar model and the BDS-2 Klobuchar model are also analyzed. The results show that the accuracy of ionospheric delay correction of the BDGIM did not change significantly before and after the completion of the BDS-3 constellation. Taking the final GIM product released by the International GNSS Service (IGS) as a reference, the ionospheric correction percentages of the BDGIM model in China, the Asia-Pacific and global regions reached 84.5%、74.6% and 64.4%, respectively. Taking the ionospheric TEC measured by BDS and GPS data of 83 global GNSS stations as a reference, the ionospheric correction percentages of BDGIM in China,Asia-Pacific and global regions are 74.3%、70.5% and 68.6%, respectively. When the BDGIM model is applied to BDS single-frequency pseudorange positioning, the three-dimensional positioning accuracy of 2.22、2.66 and 2.96 m has been achieved in China, Asia-Pacific and the global regions, respectively. Different evaluation results show that the average correction accuracy of the BDGIM model is superior to the BDS Klobuchar model and the GPS Klobuchar model.

Estimation and analysis of the multi-frequency and multi-channel DCB for BDS-3

DENG Yuanfan, GUO Fei, ZHANG Xiaohong, LIU Wanke

2021, 50(4):  448-456.  doi:10.11947/j.AGCS.2021.20200504

Asbtract ( )   HTML ( )   PDF (1170KB) ( )  

References | Related Articles | Metrics

Differential code bias (DCB) is one of the major errors in ionospheric modeling, satellite navigation, positioning, and timing. A new series of DCBs is derived from BDS multi-frequency and multi-channel signals. Firstly, this paper analyzes the code observation combination and estimable DCB type for BDS-3, establishes the mathematical model of multi-frequency and multi-channel DCB estimation, and estimates more than 20 types of DCB by using IGS data. On this basis, the precision, accuracy, and monthly stability of various DCBs are compared and analyzed comprehensively. The results indicate that the closure errors of BDS-3 DCBs are basically within 0.2 ns, which shows good precision. The estimated results have a good agreement with the DCB products provided by CAS and DLR. Six types of DCB differences with CAS are basically within 0.1 ns. Four types of DCB differences with DLR are basically within 0.2 ns. Due to the influence of error propagation, the accuracy and reliability of DCB obtained by linear transformation are not as good as DCB estimated directly. The monthly mean STD of BDS-3 DCBs is 0.083 ns, showing good medium- and long- term stability. Compared with that of BDS-2, the DCB stability of BDS-3 is relatively better.

Receiver pseudorange biases of BDS-3 satellite navigation signal: modeling and validation

MAO Feiyu, GONG Xiaopeng, GU Shengfeng, WANG Chenchen, LOU Yidong

2021, 50(4):  457-465.  doi:10.11947/j.AGCS.2021.20200584

Asbtract ( )   HTML ( )   PDF (1159KB) ( )  

References | Related Articles | Metrics

Receiver pseudorange biases are systematic pseudorange biases caused by non-ideal satellite navigation signals among different bandwidths and correlator spaces. Studies indicate that BDS-2, GPS and Galileo are all influenced by receiver-related pseudorange biases, which will affect the precise data processing among inhomogeneous receivers. In this paper, we use three observation combinations, including Melbourne-Wübbena (MW), ionosphere-free (IF) and pseudorange ionosphere- and geometry-free (IFGF) combinations, to analyze the characteristics of BDS-3 pseudorange biases based on International GNSS Monitoring and Assessment System (iGMAS) and Multi-GNSS EXperiment (MGEX) observations. The results show that there are receiver-related pseudorange biases for BDS-3 and the IF combination biases can reach up to 6 ns. According to the characteristics of BDS-3 pseudorange biases, eight groups of corrections are estimated and validated by differential code bias (DCB) estimation and single-frequency single point positioning (SF-SPP). The results indicate that the consistency of BDS-3 satellite DCB estimated by different receiver groups can be significantly improved when corrections are used. For example, the difference of C2I-C6I、 C1P-C5P and C2I-C7D DCB estimated by iGMAS and MGEX receivers decrease by 91.6%、64.7% and 71.9%, respectively. Moreover, after correcting the pseudorange bias, the accuracy of SF-SPP are improved by 13.9% and 11.0% in vertical and horizontal components, respectively.

Precise orbit determination method for BeiDou mixed constellations with layered constraints

FANG Yanan, ZHU Jun, LI Jie, WANG Chong, WANG Jiasong, ZHANG Shaoyu

2021, 50(4):  466-474.  doi:10.11947/j.AGCS.2021.20200406

Asbtract ( )   HTML ( )   PDF (1004KB) ( )  

References | Related Articles | Metrics

Considering the unique GEO+IGSO+MEO constellation design of the BeiDou Navigation Satellite System (BDS), a method for BeiDou satellite precise orbit determination that adopts different constraints and data processing strategies for different constellations is studied. And a precise orbit determination scheme with layered constraints for BeiDou mixed constellation is proposed. BeiDou satellites are divided into two parts, non-GEO (IGSO/MEO) and GEO, to be solved step by step. The public parameters calculated by GPS are used to form effective constraints on BeiDou IGSO/MEO precise orbit determination. Then the GPS and BeiDou IGSO/MEO calculation results are fixed, and BeiDou GEO satellites orbit determination is performed under strong constraints.The results of precise orbit determination tests based on real observation data show that, using the method proposed in this paper, the 3D position RMS (root mean square) of overlapping orbit differences of the BeiDou GEO satellites and non-GEO satellites reach 0.688 m and 0.042 m, yielding an improvement of 54.2% and 72.4% compared to that of using the traditional method. In addition, the satellite laser ranging (SLR) validation and static precise point positioning (PPP) of station coordinates results are analyzed to verify the orbit accuracy. The SLR validation accuracy increased by 44.3%, and the accuracy of station coordinates in horizontal and vertical directions increased by 21.5% and 20.7% on average, respectively.

Geodesy and Navigation

Variational mode decomposition method for estimation of GNSS data quality from a smartphone

PENG Zihan, GAO Chengfa, LIU Yongsheng, ZHANG Ruicheng, SHANG Rui

2021, 50(4):  475-486.  doi:10.11947/j.AGCS.2021.20200258

Asbtract ( )   HTML ( )   PDF (1388KB) ( )  

References | Related Articles | Metrics

At present, the third-derivative approach or the inter-epoch difference method is mainly used to calculate the GNSS observation noise of the smartphone, but the results of these approaches will be affected by satellite correlation and time correlation. Aimed to the GNSS data noise estimation of smartphones, we propose an approach of noise estimation method based onvariational mode decomposition (VMD). Firstly, it uses VMD to extract low-frequency components of double-difference observations, then inversely calculates the single-difference observations of each satellite, and finally calculates the observation noise of each satellite. Simulation decomposition experiments show that VMD can decompose mixed signals satisfactorily. The analysis results of the GNSS data quality from the Xiaomi 8 indicate that the pseudorange noise of GPS, BDS and Galileo are analogous. The pseudorange noise of GLONASS is about twice that of the other systems, and the phase noise of the four systems are coincident. Observation noise will not be influenced by the operating system. In addition, the carrier-to-noise ratio stochastic model is more suitable for GNSS positioning of smartphones than elevation stochastic model. Compared with the using of latter model, the single point positioning effect of smartphones can be improved by more than 25% after using the carrier-to-noise ratio model. The PPP results of the smartphone can converge to within 0.6 and 1.2 m in horizontal and vertical components, respectively.

Integer phase clock method with single-satellite ambiguity fixing and its application in LEO satellite orbit determination

SHAO Kai, YI Bin, ZHANG Houzhe, GU Defeng

2021, 50(4):  487-495.  doi:10.11947/j.AGCS.2021.20200302

Asbtract ( )   HTML ( )   PDF (996KB) ( )  

References | Related Articles | Metrics

Fixing single-satellite GPS carrier phase ambiguity could significantly improve the orbit accuracy of low earth orbit (LEO) satellite. Currently, the CNES/CLS,Wuhan University and CODE have published GPS integer phase clock products applied to single-satellite ambiguity fixing. In this paper,the integer phase clock method is used for single-satellite ambiguity fixing, and it is applied to the precise orbit determination of LEO satellite. Then, the application performances of integer phase clock products provided by different agencies in single-satellite ambiguity fixing and LEO satellite orbit determination are compared and analyzed. For GRACE-FO formation satellites, about 94% ambiguities could be fixed based on different products provided by the three agencies.Orbit solutions generated using the products from the three agencies can achieve an RMS of around 0.9 cm checked by satellite laser ranging data.Compared with ambiguity-float orbit solutions, the accuracy of absolute orbit determination with single-satellite ambiguity fixing is improved by about 30%.After fixing single-satellite ambiguities using the different products provided by CNES/CLS, WHU and CODE, respectively, the RMS of K-band ranging validation residuals for relative orbit solutions are reduced from 5.7、 5.4 and 5.3 mm to 2.1、 2.0 and 1.5 mm, respectively. The results show that the integer phase clock products provided by different agencies have similar performances in the single-satellite ambiguity fixing and orbit determination of GRACE-FO satellite.

Tightly coupled water vapor tomography algorithm for combining GNSS and MODIS signals

ZHANG Wenyuan, ZHANG Shubi, ZHENG Nanshan, DING Nan, LIU Xin, MA Pengxu

2021, 50(4):  496-508.  doi:10.11947/j.AGCS.2021.20200222

Asbtract ( )   HTML ( )   PDF (1464KB) ( )  

References | Related Articles | Metrics

Due to several significant advantages, including high-precision observation data, high spatio temporal resolution, and all-weather availability, GNSS tomography technology has become one of the most potential technologies for sensing the atmospheric water vapor. Currently, fusion of multi-source atmospheric remote sensing data has gradually become a research hotspot to make up for the geometric defects of GNSS signal in the tomography model. In this paper, the disadvantage of traditional model including the MODIS signals is analyzed at first. An improved tomography method, combining the GNSS and MODIS signals, based on the voxel node model is proposed, which introduces high-resolution MODIS PWV into the tomographic model in the form of three-dimensional signals. To assess the validity of the proposed algorithm,three experimental schemes are carried out using the 15 MODIS images and the simultaneous GNSS data derived from five GNSS stations over Xuzhou region.The experimental results show that the average number of effective signals is increased by 34.15% and the mean root mean square error(RMSE) of tomography results is decreased by 25.10% with the proposed tomography approach. Furthermore, the water vapor profiles retrieved from the three schemes are assessed using the reference profiles from the radiosonde data close to the acquisition time.It is found that in the lower layers from 0 to 2 km, the improved method retrieves better 3D distribution of water vapor than the traditional approach, which highlights that the reconstruction quality of 3D water vapor field near the surface can be optimized by including the MODIS signals.

Cartography and Geoinformation

Influence of individual characteristics on spatial cognitive ability in desktop virtual environment and real scene

HUANG Lina, ZHANG Dingrao, YING Shen, AI Tinghua

2021, 50(4):  509-521.  doi:10.11947/j.AGCS.2021.20200134

Asbtract ( )   HTML ( )   PDF (1216KB) ( )  

References | Related Articles | Metrics

Using virtual geographic environment to simulate, express and reconstruct real environment is one of the main experimental research paradigms in the domain of spatial cognitive science. To investigate whether people’s cognitive performance in virtual environment is consistent with that in real environment, this paper designs a control experiment to test the spatial cognition differences of participants in desktop virtual environment and real environment, where the spatial cognition is decomposed into three dimensions: pattern cognition, object cognition and spatial response, so that the influence of individual characteristics on spatial cognition and its environmental effects can be deduced. The results show that: ① neither environment type nor individual characteristics have significant impact on the spatial cognition; ② the participants with geographical knowledge background, rotating their mental map, and using coordinated spatial reference frame have more detailed and accurate cognition on the spatial pattern; ③ the environment type has no significant effect on the path response, but has a significant effect on the corner response. Besides, the participants can identify the correct direction more effectively in virtual environment. The positive effect of their professional knowledge is significant, and MRT level and environment type have significant joint effect. These outcomes have proved that cognitive simulation experiments can work well in a desktop virtual environment. They are also instructive to establish personalized virtual environment according to user characteristics.

A spatio-temporal network for human activity prediction based on deep learning

LI Jing, LIU Haiyan, GUO Wenyue, CHEN Xin

2021, 50(4):  522-531.  doi:10.11947/j.AGCS.2021.20200230

Asbtract ( )   HTML ( )   PDF (1213KB) ( )  

References | Related Articles | Metrics

The traditional spatio-temporal prediction methods could hardly model the complex nonlinear relationship of spatio-temporal phenomenons, thus they lack the ability to consider the influence of spatial multi-scale characteristics into the prediction results. In order to overcome this deficiency, a novel model of space-time network (MST-Net) is proposed in this paper, which transforms the regression problem of volume prediction into a discriminant model with time-space characteristics. The spatial and temporal characteristics of spatio-temporal data are extracted by multi-scale parallel convolution and gate recurrent unit respectively. Thus the extracted features are fused with the attention mechanism introduced to capture the long-term features. Finally, the prediction results can be obtained by using the full connection layers. In order to prove the reliability and validity of the model, the model is tested on two challenging social media sign-in datasets. The results indicate that the proposed model outperformed other algorithms in two prediction results evaluation indexes, namely the root mean square errors (RMSE) and mean absolute percentage errors (MAPE), which illustrate that the proposed method could achieve higher prediction accuracy and could better fit the nonlinear relationship of the space-time problem. The proposed model is suitable to predict the flow of human activities.

Research on the interactive mode of residents’ behavior based on trajectory data mining

DAI Weixiu, CHEN Zhanlong, XIE Peng

2021, 50(4):  532-543.  doi:10.11947/j.AGCS.2021.20200072

Asbtract ( )   HTML ( )   PDF (8847KB) ( )  

References | Related Articles | Metrics

As one of the effective means of transportation, taxis carry much valuable residents’ traveling information in their trajectory data. However, unprocessed trajectory data is incapable of revealing the information due to the lack of semantic information. Trajectory, data mining technology, provides a method to unveil residents activating regular patterns, which can support urban planning. This paper provides an interactive mode measuring method based on semantic information to mine the implicit relationship between residents’ behavioral purpose and trajectory. Firstly, the author discovers the semantic information from the location of the stay points. Then constructs the Interactive matrix of semantic to infer the interaction mode of behavior purpose. Finally, it takes the central area of Beijing as the research area to test the method. The test shows the association of the property of stay points and their distribution, which is in accord with the reality: here are apparent clusters around universities and business districts; the active of stay points is more durable on weekdays than on the weekends. There is a significant difference in the interactive mode between weekdays and weekends: the primary interactive mode is dwelling-working on the weekdays and is dwelling-relaxing on the weekend. This research can provide an essential reference for urban planning, resource allocation, and emergency management.

An aggregation index clustering method of natural polygon features for spatial knowledge mining

LIU Chengyi, WU Fang, GONG Xianyong, XING Ruixing, DU Jiawei

2021, 50(4):  544-555.  doi:10.11947/j.AGCS.2021.20200297

Asbtract ( )   HTML ( )   PDF (1506KB) ( )  

References | Related Articles | Metrics

Spatial clustering is one of the important methods to mining spatial knowledge. Existing methods fail to cluster natural polygon features with great differences in geometry and distribution. Hence an aggregation index is proposed to measure distribution density, and a new natural polygon feature clustering method is designed. First, the formula of aggregation index is designed and its effectiveness is verified. Then, on basis of aggregation index and the shortest distance, the affiliation relationship of adjacent polygon features is established to identify the clustering center. Thus, initial clustering group is constructed. Finally, border feature detection principle and adjacent group merging model are provided to obtain better clustering results. Experiments show that compared with MST and MSSCP, the method proposed can take the complexity of geometric and distribution characteristics into account and effectively improve the clustering results of natural polygon features.

Letters

2020 height measurement and determination of Mount Qomolangma

DANG Yamin, GUO Chunxi, JIANG Tao, ZHANG Qingtao, CHEN Bin, JIANG Guangwei

2021, 50(4):  556-561.  doi:10.11947/j.AGCS.2021.20210034

Asbtract ( )   HTML ( )   PDF (906KB) ( )  

References | Related Articles | Metrics

In order to achieve the goal that China and Nepal jointly announce the height of Mount Qomolangma, China has carried out the height measurement campaign of Mount Qomolangma from 2019 to 2020, and completed the summit survey on May 27, 2020. For the first time, airborne gravity survey was conducted in the north region of Mount Qomolangma and ground gravity data at the summit was collected, and the local gravimetric quasigeoid model and the geoid undulation of the summit in the International Height Reference System (IHRS) were determined. A variety of advanced measuring equipment, especially domestic measuring instruments played a full and active role in 2020 campaign. By means of the cross validations between multiple geodetic techniques and the strict checking computations, the accuracy and reliability of the results of 2020 campaign were ensured. Finally, China and Nepal collaborated on the data processing and jointly determined that the orthometric height (altitude) of the snow surface of the summit of Mount Qomolangma is 8 848.86 m.

Summary of PhD Thesis

Detection of terminal lake wetland and its landscape dynamics in arid regions: a case study from Ebinur Lake Wetland

WANG Jingzhe

2021, 50(4):  562-562.  doi:10.11947/j.AGCS.2021.20200066

Asbtract ( )   HTML ( )   PDF (700KB) ( )  

Related Articles | Metrics

Snow cover degradation in upper Manasi River basin of central Tianshan Mountains based on remote sensing data

LI Haixing

2021, 50(4):  563-563.  doi:10.11947/j.AGCS.2021.20200147

Asbtract ( )   HTML ( )   PDF (683KB) ( )  

Related Articles | Metrics

Research on BDS fast and precise positioning method in complex environment

CHENG Junbing

2021, 50(4):  564-564.  doi:10.11947/j.AGCS.2021.20200207

Asbtract ( )   HTML ( )   PDF (696KB) ( )  

Related Articles | Metrics

Key issues on coastal geographical environment monitoring with radar remote sensing

LI Peng

2021, 50(4):  565-565.  doi:10.11947/j.AGCS.2021.20200165

Asbtract ( )   HTML ( )   PDF (690KB) ( )  

Related Articles | Metrics

Research on multiple dynamic digital watermarking algorithms for vector geographic data

WANG Yingying

2021, 50(4):  566-566.  doi:10.11947/j.AGCS.2021.20200188

Asbtract ( )   HTML ( )   PDF (688KB) ( )  

Related Articles | Metrics

Adaptive approaches for detecting geospatial anomaly patterns

YANG Xuexi

2021, 50(4):  567-567.  doi:10.11947/j.AGCS.2021.20200192

Asbtract ( )   HTML ( )   PDF (688KB) ( )  

Related Articles | Metrics

Research on several issues related to the deformation monitoring based on Terrestrial pulsed laser scanning technology

GUO Xiantao

2021, 50(4):  568-568.  doi:10.11947/j.AGCS.2021.20200562

Asbtract ( )   HTML ( )   PDF (687KB) ( )  

Related Articles | Metrics