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How to fix integer ambiguity quickly and accurately is a key problem in carrier phase measurement. In order to improve the search rate of integer ambiguity, a integer ambiguity resolution algorithm based on beetle antennae colony search (BACS) algorithm was proposed. Through the comparison experiment with BAS algorithm, Bas-Nadam algorithm, LAMBDA algorithm and MLAMBDA algorithm, the solution rate and stability of the three-dimensional ambiguity solution were carried out. When the success rate of the solution of BACS algorithm was equal to that of LAMBDA and MLAMBDA algorithm, it can use less time to search the optimal ambiguity solution. In order to verify whether BACS algorithm is applicable in the case of high-dimensional ambiguity solution and engineering solution, the experiments of high-dimensional ambiguity solution and the application experiments of BACS algorithm under single frequency and single GPS system were carried out. The analysis and experiment show that BACS algorithm can guarantee the real-time performance and robustness of high-dimensional ambiguity solution. For 12-dimensional ambiguity solution, the average solution time is 0. 068 seconds and the success rate is 92% . For low-dimensional ambiguity solution, the solution rate is faster and the success rate is higher. In the engineering calculation of single frequency single GPS system, the positioning accuracy of x, y and z directions is ± 0. 008 meter, ± 0. 01 meter and ± 0. 01 meter respectively, which can reach centimeter-level precision positioning. [ABSTRACT FROM AUTHOR]

High-precision global navigation satellite system (GNSS) positioning technology, as a hot spot in the field of satellite navigation, has expanded the in-depth development of the location-based service area, and has been widely used in smart cities, intelligent transportation, autonomous driving and other fields. First, this paper presents the current status and development of GNSS positioning technologies.Then, it explains the common basic theories such as integer ambiguity fixation, functional model and stochastic model fusion involved in multi-frequency multi-GNSS high-precision positioning, as well as the key techniques for improving GNSS positioning performance such as the non-model error processing, the cycle slip detection and data interruption repair. Based on the innovations of basic theories and key techniques, this paper introduces four new technologies for multi-frequency multi-GNSS high-precision positioning applications developed by Tongji University GNSS team in recent years. Finally, we remark the future development trend and challenges of GNSS-based high-precision positioning. [ABSTRACT FROM AUTHOR]

As research in the field of autonomous driving has attracted much attention, driving safety has become the primary consideration. Because the point cloud scene is cluttered and the background environment interferes greatly, and with the expansion of the acquisition range, the point cloud becomes more sparse, which makes the robustness of the detection algorithm weaker. To alleviate the above problems, this study proposes a 3D object detection network based on attention mechanism and context awareness. In the point cloud processing stage, a double attention mechanism based point cloud is added to generate a point weight matrix, display and mark important point data, and suppress background noise interference. In the pseudo-map feature extraction module, the FPN(Feature Pyramid Network) module is added to reuse multi-scale features, and a Context Awareness Module(CAM) is designed to capture multi-scale context semantics. Furthermore, an Attention Guide Module(AGM) is proposed based on the source features to generate a guidance weight map with clear spatial positions, so as to alleviate the spatial ambiguity caused by redundant features. The experiments in this study are carried out on the KITTI data set test. Compared with the baseline network, the Average Precision(AP) of the proposed method for pedestrians, cars and cyclists is improved by 0.59%, 0.87% and 1.42% respectively under the difficulty index. Compared with the new baseline network, the AP of the proposed method for pedestrians is improved by 3.04%, 3.53% and 3.23% under the three difficulty levels, respectively. The results show that the proposed algorithm can effectively improve the performance of 3D object detection. [ABSTRACT FROM AUTHOR]

Existing lip-reading algorithms for Chinese sentences are inadequate at feature extraction and visual ambiguity resolution, which leads to low accuracy. Aiming at this problem, this paper proposed a lip-reading algorithm for Chinese sentences based on temporal convolutional network and 3D convolutional neural network（3DT-CHLipNet）.Firstly, it used a Temporal Convolutional Network to extract long-term features from lip dynamics sequences, which has a much larger receptive field than the Long Short Term Memory Network. Secondly, in order to minimize the visual ambiguity in Chinese lipreading, it adopted a Transformer model with the self-attention mechanism to capture the context information and improve the accuracy of sentence prediction. Finally, it introduced a temporal masking data augmentation strategy in the data preprocessing to further reduce the error rate of the algorithm. Comparison experiments on CMLR, the largest open-source Sequence-to-Sequence Chinese Mandarin Lip Reading dataset, show that the improvement in accuracy over representative lip reading algorithms for Chinese sentences ranges from 2.17%to 23.99%. [ABSTRACT FROM AUTHOR]

Most of the deep-learning based dehazing models have fixed receptive filed after the parameter are fixed. As a result, the dehazing network cannot adopt the optimal mode for dehazing each specific scene, resulting in ambiguity and distortion in the results. In view of these problems, this study proposes a dynamic receptive field feature selection dehazing network. A feature-attention atrous block with atrous convolution is designed as the basic module of the network. Multiple feature attention atrous blocks with different atrous rates are used in parallel to extract multi-scale features. Dynamic feature fusion is performed on these features to form a dynamic receptive field block. Multiple dynamic receptive field blocks are combined with residual connections to form a deep network. The features from different levels are dynamically mixed and decoded to obtain a haze-free image. The experimental results show that the proposed algorithm has a good dehazing performance on indoor, outdoor, and real hazy images, and can generate clear and natural dehazing images. [ABSTRACT FROM AUTHOR]

Objectives: In October 2019, the International GNSS Service(IGS) began the third data reprocessing campaign(repro3). To enable more robust ambiguity resolution(AR) in precise point positioning (PPP), one of IGS important tasks is to combine satellite clock and code/phase bias products. Methods: We elaborated the precise satellite clock product model, code/phase bias product model, as well as prior corrections and specific processes for the combination of global navigation satellite system(GNSS) satellite clock and code/phase bias products. What􀆳s more, entrusted by the IGS Analysis Center Coordinator, we combined the clock/bias products of repro3 from 2000 to 2020 successfully. Results: Through the statistics of the combination, it is concluded that the integrity rate of combined clock can reach more than 95% after stabilization, which is superior to most of the products of IGS Analysis Centers. The average root mean square error of GPS and Galileo satellite navigation system satellite clock reach 6.13 ps and 5.63 ps respectively, which prove that the correction models in the combination can significantly improve the consistency. The average weight of Graz University of Technology participating in the combination reaches 21.83%, which has better precision than that of other analysis centers. The weight of phase/integer clock is higher than that of legacy clock, with better stability and precision. Furthermore, 103 stations with uniform global distribution were selected for the static PPP-AR solution to validate the positioning precision of the combined products. The results showed that the average fixed rates of GPS wide and narrow-lane ambiguity based on combined products are 90.16% and 86.72% respectively, and those of Galileo are 97.11% and 93.77% respectively, which are about 1-5 percentage points higher than those based on Center for Orbit Determination in Europe (COD) repro3 products. The average positioning precision based on combined products in the east, north and high directions is 0.154, 0.178 and 0.542 centimeters respectively, which is 20% to 30% higher than COD. Conclusions: The multi-GNSS satellite clock and code/phase combination method can effectively solve the problems of the consistency among products of analysis centers,and enable more robust ambiguity resolution in PPP-AR. Moreover, the combined products have been officially downloaded (IGSMAIL-8248:https://cddis.nasa.gov/archive/gnss/products/repro3/). [ABSTRACT FROM AUTHOR]

Objectives: Global navigation satellite system (GNSS) satellite chip shape distortions lead to individual biases in the pseudorange measurements. These biases are the results of the correlator's tracking response and thus depend on the correlator and front-end design of the receiver. As a result, different receivers are likely to exhibit inconsistent biases, called receiver-related pseudorange biases. The researches show that the receiver-related pseudorange biases cannot be absorbed by clock offset, which will affect GNSS precision applications. Methods: We estimate the receiver-related pseudorange biases of global positioning system (GPS)/BeiDou satellite navigation system (BDS) /Galileo satellite navigation system (Galileo) from 9 short/zero-baselines stations from the multi-GNSS experiment network using double difference method. The baselines are divided into three groups according to the combinations of two receivers of one baseline. Results: The results indicate that the receiver-related pseudorange biases of receivers with different manufacturers even the same manufacturers with different models cannot be neglected. For base‐lines with receivers from different manufacturers,the inconsistences of pseudorange biases can reach up to 160 cm. Conclusions: Among GPS, Galileo and BDS, Galileo shows the smallest pseudorange biases, while BDS in general is the largest. Furthermore, the stability of pseudorange biases is analyzed, the results suggest that estimated receiver-related pseudorange biases are quite stable with the standard deviation less than 12 cm for the three systems. We investigate the effect of receiver-related pseudorange biases on integer ambiguity resolution and pseudorange relative positioning, with the pseudorange biases correction, the root mean squares of fractional parts of double difference Melbourne ‐Wübbena combination are decreased by 17%, 22%, and 14% for GPS, BDS, Galileo, respectively. An improvement of pseudorange relative positioning accuracy is also confirmed, the 3D positioning errors of GPS, BDS, Galileo are reduced from 84.4, 77.3 and 60.0 to 80.1, 72.1 and 57.0 cm, respectively. [ABSTRACT FROM AUTHOR]

Objectives: BeiDou-3 satellite navigation system (BDS-3) has been officially completed and provides services, network real time kinematic(RTK) is the main means to improve positioning accuracy, we present a long-distance undifference network RTK method based on BDS multi frequency and multi system observation data. Methods: First, the ambiguity resolution model considering atmospheric error parameters is used to determine the integer ambiguity of multi-frequency carrier phase of long-distance BeiDou satellite navigation system (BDS) reference station.Then,the double difference integer ambiguity between reference stations is converted into non‐difference integer ambiguity of each reference station through linear change,and calculate the undifference observation error of each reference station. Considering the weakening of spatial correlation of observation errors between long-distance stations.According to the difference of error characteristics,obtain the correction number of classified undifference error of reference station network.Finally, by inverse distance weighted interpolation method, we calculate the error correction of mobile station, high precision positioning for users. Results: Select the measured data of long-distance continuous operation reference station network for experiment, the results show that: Compared with BeiDou-2 satellite navigation system (BDS-2), BDS-3 increases by 15.7%, 28% and 11.9% in E, N and U directions respectively. Compared with GPS, the positioning performance is equivalent or even better. The ambiguity fixing success rate and convergence time of multi-frequency data are better than GPS dual-frequency data. Dual system positioning results are better than single system, both of which can achieve centimeter level positioning of mobile stations. Conclusions: This method can avoid the correlation effect of double difference observations, high efficiency of spatial error calculation, mobile station positioning is more flexible, shows the advantages of BDS multi frequency observation data. [ABSTRACT FROM AUTHOR]

Loop closure detection can eliminate the accumulated error of visual SLAM, which is of great significance to the SLAM system. Among them, the widely used visual bag-of-word model algorithm has the problem of visual word identity and ambiguity, which affects the loop closure detection effect. To improve these problems and loop back detection effect, this paper proposed a loop closure detection algorithm based on soft-assigned SIFT features. The algorithm allocated the SIFT feature points extracted from the image to several words with the closest Euclidean distance, according to the distance sorting and weighting, and removed the feature points that were far away from the words to generate more discriminating descriptors. In addition, when filtering candidates, the algorithm added the proportion constraint of the same word feature points and the stability constraint of word shift to filter out a few candidates. In the experimental results, the algorithm compared with the traditional visual bag-of-words model and several loop closure detection algorithms in recent years, the recall rate at 100% accuracy rate improved under three data sets, and the average image query time was about 40 ms. The results show that the algorithm can improve the loop detection effect and ensure the real-time performance. [ABSTRACT FROM AUTHOR]

In order to fix the integer ambiguity quickly and accurately, this paper proposed a new ambiguity search algorithm based on measurement accuracy constraints to solve the problems of the LAMBDA algorithm, such as the wide search range of the integer ambiguity and the low search efficiency. When the least squares problem got optimally weighted, the algorithm took the carrier phase measurement accuracy as the constraint condition to test the fixed ambiguity solution on the basis of the stan-dard differential evolution （DE） algorithm. This algorithm solved the influence of different satellite altitude angles, and could achieve 99% success rate when solving 3D integer ambiguity. Compared with the MLAMBDA algorithm, the standard DE algorithm and the adaptive weighted differential evolution （AWDE） algorithm, the proposed algorithm further improves the efficiency and success rate of ambiguity resolution. [ABSTRACT FROM AUTHOR]

Objectives: In order to make full use of the observed value information of each frequency, an undifferenced and uncombined integer ambiguity resolution method between BeiDou satellite navigation system (BDS) long-range reference stations is proposed. Methods: First, the error observation equation is established directly by using the observations of different frequencies, and the relative zenith tropospheric wet delay error and ionospheric delay error are estimated by random walk strategy to increase the constraint between epochs. Second,a linear calculation method of undifferenced integer ambiguity real-time is used to obtain the undifferenced integer ambiguity of all satellites in the current epoch of the reference network. It solves the problem that ambiguity needs to be inherited or re-superimposed on normal equations in the reference star transformation. Because the information of each frequency observation is fully utilized, the influence of linear combination amplification noise on integer ambiguity fixing is avoided, and the ambiguity fixing success rate of uncombined method is much higher than that of ionosphere-free combination method. Results and Conclusions: The results show that the average fixed speed of ambiguity of each reference station is 20 epochs (sampling interval 1 s). The integer ambiguity resolution of the carrier phase of the reference station can be realized quickly. [ABSTRACT FROM AUTHOR]

Entity linking studies are mainly focused on the fields of medical care, biology and news, but less on the field of civil aviation. Therefore, this paper carried out a research on entity linking task in civil aviation domain, and found that there were many entity variants and less ambiguity in entity linking. To solve these problems, this paper proposed an entity linking framework based on semantic inference and a negative sampling strategy for enhancing the robustness of the framework. This paper conducted comparative experiments on the civil aviation field dataset. Experimental results show that the performance of the proposed framework is better than the existing benchmark frameworks, and the effectiveness of the negative sampling strategy is verified through ablation experiments. With the negative sampling strategy, the Acc@ top1 of the proposed framework is as high as 0. 875. [ABSTRACT FROM AUTHOR]

Traditional text keyword extraction methods ignore the contextual semantic information and cannot solve the problem of ambiguity of a word, so the extraction effect is not ideal. Based on the LDA and BERT models, this study proposes the LDA-BERT-LightGBM (LB-LightGBM) model. The LDA topic model is selected to obtain the topic of each review and its word distribution, candidate keywords are filtered out according to the threshold, and the filtered words and the original review text are spliced and input into the BERT model. The word vector training is performed to obtain the word vector containing the text topic, so the text keyword extraction problem is converted into a two-classification problem through the LightGBM algorithm. The textrank algorithm, LDA algorithm, LightGBM algorithm and the proposed LB-Light GBM model are compared through experiments on the accuracy rate P, recall rate R and F1 of text keyword extraction in the present study. The results show that when TopN takes 3～6, the average value of F1 is 3.5% higher than that of the optimal method, indicating that the extraction effect of this method is generally better than that of the comparison method selected in the experiment, and the text keywords can be found more accurately. [ABSTRACT FROM AUTHOR]

Aiming at the problems of low sampling frequency, low resolution and high noise in video ghost imaging reconstruction, an aggregated three-dimensional target matching filtering method was proposed. Firstly, each frame of the ghost imaging video is block-matched with the frame to be optimized and each frame of images after block matching is arranged to form a three-dimensional matrix according to the time sequence. According to the frame sequence of each frame picture, different frame weights are assigned to it. Then the matrix is subjected to three-dimensional weighted median filtering. After under-sampling simulation and experimental comparison of moving targets, the method proposed has not only lower noise figure and better structure retention, but also a better subjective evaluation compared with the existing three-dimensional filtering methods. Compared with the original experimental restoration graph, the proposed method reduces the noise figure and edge ambiguity by 34.25% and 6.86%, respectively, and the Brisque subjective evaluation was improved by 45.84%. [ABSTRACT FROM AUTHOR]

Objectives: BeiDou-3 navigation satellite system (BDS-3) has been fully completed and pro‐ vides reliable positioning, navigation, and timing services to global users. In order to achieve compatibility and interoperability with other global navigation satellite systems (GNSS), B1C and B2a signals have been modulated by BDS-3 based on BDS-2, which enable frequency multiplexing with E1 and E5a signals of Galileo. The inter-system biases (ISBs) are important for the fusion processing of different GNSS. Methods: This paper proposes an ISB estimation and application model based on the single-differenced observations and analyzes the ISBs between the overlapping frequencies of BDS-3 and Galileo. Based on several receivers of the new trackable BDS-3 signals, the characteristics of ISBs between BDS-3 and Galileo are revealed, and the real-time kinematic (RTK) positioning performance of BDS-3 and Galileo is analyzed. Results: The results show that the ISBs of B1C-E1 and B2a-E5a exist in different types of receivers but not in the same type of receivers. In addition, compared with BDS-3-only and Galileo-only, the combination of BDS-3 and Galileo has an improvement of more than 10% in both the success rate of ambiguity resolution and positioning accuracy. Conclusions: The multi-constellation RTK positioning performance with the introduction of ISBs is more advantageous than that of a single constellation [ABSTRACT FROM AUTHOR]

Aiming at the problem of rover positioning in Chinese Mars exploration mission Tianwen-1, the related research and accuracy analysis have been carried out. Methods: According to the existing measurement and control system and considering that the rover has no ground ranging data, we proposed a method to locate the rover using same-beam very long baseline interferometry (SBI) data of the orbiter and rover. Since it is not possible to determine the ambiguity using SBI and ranging data while deter‐ mining the orbit and positioning the rover at the same time, the proposed method which only uses SBI data for the rover positioning under the fixed orbital situation is analyzed. Results: The results show that the rover positioning error decreases with the increase of orbital accuracy. If the orbital accuracy is increased from 1 km to 100 m or 10 m,the rover positioning error using 6-hour SBI data can be reduced to hundreds of meters. Conclusions: More data can further reduce the positioning error and the positioning accuracy can be improved obviously with an elevation constraint. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the attribute weights and decision-makers’ weights were unknown in the emergency decision-making process of public health emergencies, this paper proposed a Pythagorean fuzzy reductive BM operator decision-making method based on DEMATEL and trust network, which took into account the subjective and objective relationships to ensure the integrity of the emergency assessment system. Firstly, considering the important influence of key factors on the emergency decision-making of public health emergencies, it identified and determined attribute weights by the DEMATEL method, and taking the complex and diverse backgrounds of emergency decision-making as the entry point, it used the trust propagation path to improve the trust relationship and built a hybrid trust network that integrated the initial trust degree and preference similarity to obtain decision-makers’ weights. Secondly, considering the strong correlation between the properties of the emergency assessment, it introduced a Pythagorean fuzzy reductive BM operator based on the improved similarity measure and score function, and calculated the comprehensive evaluation value and the ranking of the plan. Finally, this paper applied the method to the emergency management assessment of sporadic cases in hospitals during the normalization of epidemic prevention and control period. It verifies the reliability and reasonable effectiveness of the method. [ABSTRACT FROM AUTHOR]

The correct fixation of the ambiguity has a vital impact on GNSS high-precision positioning and navigation. To address the threshold determination problems existed in conventional difference tests, this paper proposes a threshold determination method based on fixed correct rates under the framework of integer aperture estimation. This method can not only select a reasonable difference test threshold according to the ambiguity's dimension, but also ensure a reliable accuracy, which has certain theoretical significance and practical value. [ABSTRACT FROM AUTHOR]

Objectives: The stochastic model of observation information describes the accuracy of observation information and its correlation, and also plays an important role in parameter estimation, quality control and accuracy evaluation. In the process of global navigation satellite system (GNSS) precision positioning, an accurate stochastic model is essential for improving the accuracy of float solution, enhancing the success rate of ambiguity resolution, increasing the accuracy of gross error detection, and obtaining the accurate and reliable positioning results. Methods: An optimization method for stochastic model of BeiDou navigation satellite system (BDS) is proposed by handling the properties of four classic elevation-dependent stochastic models based on the relationship between BDS satellite observation information and elevation. Firstly, the accuracy of BDS four-frequency observation information is evaluated by the simplified Helmert variance estimation method. Then, the model parameters could be fitted based on the estimated precision of observation information. Finally, the statistical characteristics of four stochastic models, including piecewise function, sine function, cosine function and exponential function, are tested by the overall test and ω-test methods. Results: The results show that the accuracy of pseudorange and carrier phase for BDS-3 satellite are related to elevation, and the correlation degree is different by GNSS observation types. The stochastic model of exponential function shows the best performance in the fitting error, the overall test and the ωtest. The maximum fitting errors of pseudorange and carrier phase are 0.029 m and 5.484 mm, respectively. The false alarm rates of the overall test for the float solution and the fixed solution are 5.1 % and 4.9 %, respectively. In addition, the maximum false alarm rates of the ω-test are 5.8 % for the pseudorange and 6.8 % for the carrier phase. Conclusions: The stochastic model of exponential function can get the shortest convergence time and the highest positioning accuracy for BDS-3 quad-frequency precise point positioning. It can also accurately describe the accuracy of BDS observation information and improve the accuracy and reliability of BDS precise positioning results. [ABSTRACT FROM AUTHOR]

Solving the problem of ambiguity of text words is important for text representation, and it can accurately define the semantic characteristics of words in a specific context. Aiming at the polysemy and contextual characteristics of words, this paper proposed a semantic disambiguation model of SCDVAB. The main innovations are: Based on the partition average technology, it can convert scene corpus into document embedding, and introduce anisotropy to improve the sparse composite document vector（SCDV） algorithm of soft clustering to improve the contextual representation ability of BERT; and then it can improve the ability of text semantic disambiguation by embedding the BERT words after adjusting the anisotropy as a static word vector. Through many experiments, SCDVAB model is significantly better than the traditional text disambiguation algorithm. SCDVAB model can effectively improve the comprehensive performance of text semantic disambiguation. [ABSTRACT FROM AUTHOR]

Objectives: High-accuracy and high-reliability satellite orbit is the fundamental requirement for precise applications of low earth orbit (LEO) satellites. Due to the uncalibrated phase delay (UPD) originated from receivers and satellites, the phase ambiguity cannot be estimated as integer values. Fixing phase ambiguity to proper integer number is one of the key issues to improve the precise orbit determination (POD) accuracy. The algorithms and methods of single-difference (SD) ambiguity resolution (AR) based on integer clocks are demonstrated. The reduced dynamic POD and kinematic POD with SD AR are implemented and the performance is analyzed. Methods: Integer clock is the precise clock product that absorbs satellite UPD. By applying integer clock products, the receiver UPD can be eliminated by forming SD am-biguities between two global navigation satellite system (GNSS) satellites. And the SD ambiguity recover its integer nature and can be fixed to integer value by a rounding strategy. The onboard gravity recovery and climate experiment follow on (GRACE-FO )data (GRACE-C/D) and integer clocks from Centre National d’ Etudes Spatiales/Collecte Localisation Satellites (CNES/CLS) of April and May 2019 was employed to evaluate the improvement of reduced dynamic POD and kinematic POD accuracy with SD AR. Results: The wide-lane ambiguity fixing rates of both reduced dynamic and kinematic POD reach 99% and the narrow-lane fixing rates are about 95%. For reduced dynamic POD, the 3D root mean square error (RMSE) values of overlapping orbit difference reduced from 7.1 mm and 7.4 mm to 4.2 mm and 3.6 mm for GRACE-C/D, respectively. The standard deviation values of satellite laser ranging (SLR) residuals decrease from 15.9 mm and 14.4 mm to 10.8 mm and 11.0 mm, with improvements of 32% and 24%. Besides, the RMSE values of K-band ranging residuals reduced from 8.0 mm to 2.9 mm, demonstrating that SD AR can also improve the relative position accuracy of LEO satellites. As for kinematic POD, the 3D RMSE values for orbit difference with precise science orbit (PSO) of ambiguity-float solution are 37.5 mm and 36.4 mm, while those of ambiguity-fixed solution are 27.7 mm and 25.5 mm, with improvements of about 28%. Moreover, the SLR residuals results also improved by 20%. Conclusions: With the integer clock products, SD AR can be achieved using onboard observations of a single LEO satellite. The SD AR can significantly improve both the reduced dynamic and kinematic POD accuracy of LEO satellites. [ABSTRACT FROM AUTHOR]

Objectives: Precise point positioning (PPP) combines the advantages of standard point positioning (SPP) and relative positioning, which can achieve centimeter level positioning. With the development of BeiDou satellite navigation system (BDS), more and more BDS satellites begin to provide global positioning, navigation and timing services, which also promotes the development of multi⁃frequency and multi⁃system PPP. For a long time, because of the atmospheric delay and hardware delay of satellite and receiver, the ambiguity of PPP is not an integer. PPP needs a long time to converge, which greatly limits its application. The ambiguity can be restored to integer and the convergence time can be shortened with the help of fractional cycle bias (FCB). Methods: In order to improve the effect of precise point positioning⁃am biguity resolution (PPP⁃AR) of BDS as a whole, we estimate the FCBs of GPS and BDS based on the observation data from August 1 to August 31 in 2020 of globally distributed stations. The single difference between satellites is used to eliminate the influence of hardware delay at the receivers, and the single difference ambiguity vector is solved by the whole network adjustment to obtain the FCB estimation of each satellite. Results: The results of the time series of BDS⁃3 wide lane (WL) and narrow lane (NL) FCBs show that the WL FCBs has long term stability, the change of BDS 3 WL FCBs in 31 days is less than 0.2 weeks, and the change of GPS WL FCBs is less than 0.1 weeks. The FCBs of BDS⁃3 NL can keep stable for a period of time, and the change is less than 0.1 weeks. The percentages of GPS WL and NL FCBs residuals within 0.15 weeks are 99.8% and 99.3% respectively, and the percentages of BDS 3 are 99.7% and 98.1% respectively. In order to reflect the improvement effect of FCBs on PPP, static and dynamic PPP⁃AR tests were carried out at 8 stations around the world. The results show that under the static condition, the average fixed time and convergence time of BDS⁃3 are 31.5 min and 24.9 min respectively, which is 24.8% shorter than the float PPP. The errors in E, N and U directions are 1.03 cm, 0.60 cm and 1.72 cm respectively, and the fixed rate is 89.8%. Under the dynamic condition, the average fixed time and convergence time of BDS⁃3 are 33.3 min and 50.7 min respectively, which is 17.4% shorter than the float PPP. The errors in E, N and U directions are 2.57 cm, 2.29 cm and 3.71 cm respectively, and the fixed rate is 83.9%. Conclusions: PPP⁃AR can shorten the convergence time of PPP to a certain extent, but the improvement of positioning accuracy is not obvious after complete convergence. BDS 3 FCBs stability is limited by precision products and observation data, and its PPP⁃AR is slightly worse than GPS. [ABSTRACT FROM AUTHOR]

Objectives: It is difficult to effectively evaluate and weaken the impact of observation environment change on data quality. To solve the problem, this paper studies a multi-point hemispherical grid model which can be applied to various satellite navigation systems.Methods: It integrates the observations of different global navigation satellite system (GNSS) satellite pairs in different observation periods to establish a global optimal multipath model. GNSS multipath error can be estimated effectively using multi-point hemispherical grid model (MHGM), image-based inverse of multipath effect and reflect the orientation of interference sources in the observation environment around stations. Results: To a certain extent the observation environment around stations can be modelled. The test under deliberate high multipath environment reveals that using MHGM significantly improved the root mean square error (RMSE) of the double-differenced carrier phase observation residuals in the period of fixed ambiguity, reducing the mean RMSE from 0.983 cm to 0.318 cm, a 67.7% improvement. In addition, the abnormal areas with large value of correction in the MHGM results is consistent with the direction of the baffle mounted at the corresponding stations. This model indicates multipath effects on GNSS carrier phase observations in different directions from the station. The test with International GNSS Service historical observations shows MHGM can effectively reflect the influence of changing multipath interference around stations on carrier phase observations, with an average improvement of 29.5% in the RMSE of residuals over the past 18 years. Conclusions: This model can be used to evaluate the changes in observation environments surrounding stations over time. It has potential application value to improve the accuracy and reliability of augmentation system products. [ABSTRACT FROM AUTHOR]

Aiming at the problem of low reliability of real-time ambiguity fixation in kinematic-to-kinematic relative positioning based on single-frequency carrier phase, a DGNSS / INS-based smoothed INS-aided ambiguity resolution strategy for kinematic-to-kinematic relative positioning was proposed, to improve the universality of high precision positioning for low cost receivers. Firstly, a kinematic-to-kinematic relative positioning model was established based on double-difference (DD) pseudorange and carrier phase observations. Secondly, a Kalman filtering was applied to the inertial navigation data, and the DD observation equations were reconstructed using the prediction pseudorange by filtered INS-derived position. Meanwhile, the INS-derived position constraint equation was complemented. The high precision ambiguity float solutions and their covariance matrix were obtained, then LAMBDA algorithm was used to fix the ambiguity and ratio test was conducted. Finally, the INS errors were feedback corrected by DGNSS / INS tightly coupled Kalman filtering results to maintain INS high precision navigation. The experimental results of testing data show that the method adopted can effectively increase the accuracy of ambiguity float solution, reduce the search space for ambiguity, and improve the success rate of ambiguity fixation. By comparing the results of without INS aided, with INS aided and with smoothed INS-aided, the success rate of the three methods were 92. 3%, 99. 1% and 99. 6%, respectively, and finally achieve dynamic relative positioning in centimeters. [ABSTRACT FROM AUTHOR]

Objectives: In precise point positioning (PPP) technology, the correct fixing of ambiguity is al⁃ ways an essential part of achieving high-precision positioning. However, the wrong fixing of ambiguity will lead to serious positioning errors. Therefore, it is necessary to optimize the selection of the ambiguity sub⁃ set to ensure a more reliable fixing of PPP ambiguity. Methods: This paper proposes a PPP partial ambiguity resolution (PAR) method that combines quality control and Gram-Schmidt orthogonalization. By utilizing the multi-GNSS(global navigation satellite system) experiment (MGEX) observations in the un-differenced and un-combined PPP model, the PAR method based on Gram-Schmidt orthogonalization was com⁃ pared and analyzed with the selected reference satellite method with maximum elevation, and the performance of ambiguity resolution and positioning was assessed under the multi-GNSS conditions. Results: Experimental results show that the average epoch fixing rate of each day and each station based on the Gram Schmidt method is improved by 7.74% and 11.46% in the static mode, and 7.90% and 7.78% in the pseudo-kinematic mode, respectively, compared with that of the selected reference satellite method considering the maximum elevation. Meanwhile, time-to-first-fix (TTFF) of each day and each station based on the Gram-Schmidt orthogonalization can be significantly reduced by 22.30% and 25.42% in the static mode, corresponding to an improvement of 20.44% and 19.65% in the pseudo-kinematic mode, respectively, compared with that of the selected reference satellite method considering the maximum elevation. As far as multi-GNSS PPP AR is concerned, multi-GNSS PPP AR has a significant improvement on the convergence time of BDS (BeiDou navigation satellite system) only. The convergence time of horizontal components is shortened by 20.00 min on average at 95% confidence level, and the vertical components are shortened by 19.00 min on average. For the positioning accuracy aspects, the positioning accuracy of horizontal components is improved by 1.50 cm on average, while that of vertical components is improved by 1.12 cm on average. Conclusions: The PPP PAR algorithm based on the Gram-Schmidt method can significantly improve the performance of ambiguity resolution and positioning accuracy. [ABSTRACT FROM AUTHOR]

Amid the intensifying China-US strategic game, the ROK, as both an ally of the United States and an important partner of China, is facing increasing pressure to pick sides. Within the ROK, there have been fierce debates on how to respond, with various opinions coming up including siding with the US to balance against China, taking the free ride of China's development, focusing on the ROK's own independent strength, maintaining the status quo, and transcending the conventional diplomatic framework. At the beginning of the Moon Jae-in administration, the ROK kept strategic ambiguity and avoided taking sides based on the recognition that China and the US are equally important. However, influenced by a series of internal and external factors, the Moon government in its later stage demonstrated increasing tendency to follow the US while sticking to the balance between the two powers. Under the conservative presidency of Yoon Suk-yeol, the ROK may move closer to the US given the uncertainty of his policy toward North Korea, the increasing conservative tendency domestically, and the impacts of the Russia-Ukraine conflict. However, based on the close economic ties between China and the ROK, the progressive majority in the National Assembly and the ROK's long-standing pragmatic diplomatic traditions, the momentum and the possibility still exists for China-ROK relations to maintain steady development. [ABSTRACT FROM AUTHOR]

Objectives: Satellite clock difference (SCB) is affected by many factors, such as data discontinuity, jump and gross error, among which the gross error is the most representative. Traditional SCB gross error detection method is the median absolute deviation (MAD) method. Methods: With the single difference of SCB as the research object, we analyzed the working principle of traditional MAD method. In view of the deficiency of traditional MAD in SCB gross error detection, an improved gross error detection method was proposed. Firstly, the ambiguity in mathematical expression was eliminated by optimizing the model structure, and then dynamic MAD was generated based on the basic principle of ridge regression, which effectively overcame the interference of some single difference data with significant trend changes on gross error detection. Results: We used International Global Navigation Satellite System Service precision SCB as reference for experiments. Compared with traditional MAD, the detection accuracy and recall rate of the proposed method were better than traditional MAD, especially for the data with obvious change of trend characteristics. Conclusions: The proposed method has obvious advantages in gross error detection accuracy and recall rate and has high application value. [ABSTRACT FROM AUTHOR]

The sparse array has ambiguity characteristics, which makes the traditional ISM method unable to be directly applied when the amplitude and phase errors or position errors of the array elements exist. In view of this defect, the study utilizes the principle of DOA estimation algorithm based on medium defuzzification in linear arrays, extends this algorithm to two-dimensional sparse planar arrays, and deeply studies the influence of medium parameters on the suppression effect by introducing the concept of suppression degree. This study combines the algorithm with the classic ISM method to establish a new sparse planar array amplitude and phase error estimation algorithm. The simulation results show that this proposed method can not only make the blur angle suppression degree up to 17 dB under the condition of reasonable selection of media parameters, but also can estimate the amplitude and phase error under the premise of obtaining the accurate angle, which improves the robustness. [ABSTRACT FROM AUTHOR]

In a complex monitoring environment, GNSS signals, which are extremely susceptible to environmental interference, can produce multipath errors, and the observation data contain a large number of poor observation values, resulting in reduced GNSS monitoring accuracy or even unavailability. Considering that the base station in the monitoring network is usually deployed in an open and unobstructed environment, and the same satellite information tracked by the base station and the monitoring station has a strong correlation, the method of identifying multipath errors in GNSS observation data based on prior information of base station's signal-to-noise ratio(SNR)was proposed. This method utilizes the strong correlation between satellite SNR observations and multipath errors, identifies poor data seriously affected by multipath through making inter-station differences in SNR observations, and removes them to resist the multipath effects of complex monitoring environment. Taking the monitoring environment of one landslide with serious occlusion in Sanmenxia area of Henan as an example, the verification based on the measured data shows that the proposed method can effectively identify the poor observation values with serious multipath effect affected by mountains, vegetation and artificial facilities, has stronger environmental adaptability, and significantly improves the fixed rate of ambiguity and positioning accuracy. Compared with the traditional fixed cut-off(TFC)model and the azimuth-dependent elevation mask(ADEM)model, the proposed method's ambiguity fixed rates are improved by the average of 39.6% and 28.6%, respectively; the positioning accuracy of the fixed solution is better than 4 mm in the E and N directions, and better than 9 mm in the U direction. [ABSTRACT FROM AUTHOR]

Objectives: The frequency division multiple access technology of GLONASS causes IFB (inter‑ frequency bias) when the receiver receives signals from different satellites, which makes it difficult to fix the ambiguity of GLONASS. It is an important factor that makes the orbit accuracy of GLONASS inferior to that of GPS （global positioning system） . At present, only CODE (centre for orbit determination in Eu‑ rope) among the IGS (international GNSS service) analysis centers provides GLONASS ambiguity ‑fixed orbits. To improve the orbit accuracy of GLONASS, it is necessary to develop a method to fix ambiguity in GLONASS all baseline and all constellation orbit determination. Methods: Based on a GLONASS ambiguity fixing method for long baseline, GLONASS ultra‑rapid orbit determination is propsed. Firstly, the float ionosphere‑free ambiguity with a wavelength of about 5.3 cm is solved. Then the Inter‑frequency phase bias (IFPB) rate will be determined by interval search method to correct the IFPB. After the IFPB is eliminated, the double difference ionosphere‑free ambiguity can be fixed and then the ambiguity‑fixed ultra‑rapid orbit is obtained. Results and Conclusions: The effect of this method in the GLONASS ultra‑rapid orbit determination is verified and analyzed by using globally distributed stations. The results show that the IFPB rates are relatively stable within one month. The fixing ‑rate of GLONASS satellite ambiguity after correcting IFPB decreases with the increase of baseline length. The highest fixing‑rate is 95%, the lowest is 88%, and the average is 94%. After the ambiguity is fixed, compared with the CODE product, the accuracy of the ultra‑rapid orbit is increased by 26.8% and 18% for the calculation part and the 3‒6 hour forecast part respectively, the accuracy of the inner precision is increased by 20% and 13% for the calculation part and the 3 ‒ 6 hour forecast part respectively, which indicates that this method can effectively fix the GLONASS ambiguity and improve the accuracy of ultra‑rapid orbit. [ABSTRACT FROM AUTHOR]

Objectives: Network real-time kinematic (RTK) technology can provide real-time and high-precision positioning service for users over the wide range, however, the current technology depends on high density of satellite navigation and positioning (SNAP) reference station network. To satisfy the high-precision positioning requirements based on the sparse reference station network, this paper recommends a net- work RTK service method based on virtual atmosphere constrait (VAC).Methods: Firstly, a non-combined double- difference observation model is constructed to solve and fix the network RTK baseline ambiguity quickly. Then, the baseline atmospheric delay is extracted and the slant path ionosphere and zenith trop- sphere are established respectively. Finally, the interpolated atmospheric delay and its accuracy information are regarded as virtual observations to improve the positioning performance of the terminal RTK. Based on a 205.1 km station spacing SNAP network from a northwest region， China, six rover stations inside and outside the network are used for termininal RTK verification. Results: The results show that the VAC net- work RTK service method can meet the needs of high-precision positioning users over large-scale reference networks. The terminal positioning accuracy and initialization speed by the VAC method are significantly improved by 61.64% and 9.96% compared with the traditional virtual reference station method. In this service mode, the average horizontal and vertical root mean squares of the fixed solution for the six terminals are 1.19 cm and 2.73 cm. Initializing RTK solution by a lot of times, 88.78% of periods can be fixed within 2 epochs for the six rover staions. Conclusions: The VAC service mode has good adaptability to both users inside and outside the large-scale SNAP base station network. [ABSTRACT FROM AUTHOR]

Aiming at the problem of ambiguity caused by boundary segmentation errors caused by word segmentation in Chinese relation extraction, and the problem of multiple relations involved in the overlapping of entity pairs, this paper proposed joint extraction method based on word mixing. Firstly, for the word segmentation boundary problem, the embedding layer combined word vectors on the basis of word vectors, and added position information to ensure the correct order between words. Secondly, the model introduced a hybrid expanded convolutional network for feature extraction with different granularity and longer distance. Finally, it used the hierarchical labeling method to mark the corresponding relationship and object entity through the obtained main entity information, and each main entity could correspond to multiple relations and object entities. Compared with other relation extraction methods on the same Chinese data set, the experimental results show that the extraction effect of this method is the best and also shows better stability. [ABSTRACT FROM AUTHOR]

Current sentiment analysis models usually use word2vec, Glo Ve and other methods to generate static word embedding, and traditional convolutional or recurrent depth models cannot fully focus on the context, extract insufficiently features, and reduce the accuracy of sentiment judgment. This paper proposed a Chinese text sentiment analysis model based on ELMo and Bi-SAN. Firstly, through ELMo language model training, the model got the word vector that integrated the word itself and context information to solve the problem of ambiguity of a word. Meanwhile, it used pre-trained skip-gram algorithm to replace the embedding layer of the randomly initialized ELMo model and improved the convergence speed of the model. Then the model used Bi-SAN to extract features. Due to the self-attention mechanism, Bi-SAN could fully focus on the context of each word and extract features more comprehensively. Compared with multiple existing sentiment analysis models, the proposed model achieves higher F, in the hotel review dataset and the NLPCC2014 task2 Chinese dataset, which validates the effectiveness of the model. [ABSTRACT FROM AUTHOR]

The undifferenced ambiguity is recovered to the integer characteristics after the fractional cycle bias (FCB) product correction, which significantly shortens the convergence time of precision point positioning (PPP). When the uncombined FCB products are estimated, the original L1 and L2 FCB cannot be accurately separated due to the limitation of global ionospheric model accuracy.On one hand, due to the limitation of the accuracy of global ionospheric grid model, L1 and L2 ambiguity cannot be separated accurately in real‐time, which makes the inconsistent for user end using the uncombined FCB products. On the other hand, due to the difference between the ionospheric combined FCB products and the uncombined FCB products, the user end with uncombined PPP model cannot use the ionospheric FCB products. Methods：A partial ambiguity resolution method for uncombined PPP using the ionosphere‐free combined FCB product is proposed, which considers the consistency between the algorithm of generating the ionosphere‐ free combined at server end FCB product and the algorithm of the uncombined ambiguity resolution at user end. Constructing the narrow‐lane ambiguity by using the raw ambiguity and wide‐lane ambiguity of single difference between satellites, the ionosphere‐free combined FCB product is used to fix the ambiguity step by step. Consisting of about 120 global multi ‐ GNSS experiment （MGEX） stations are used to generate the ionosphere‐free combined FCB and uncombined FCB products, and 10 stations which are not in the service end are selected for evaluation and validation. For the server end with 120 MGEX stations, 97.3% of the wide‐lane ambiguity residuals and 96.8% of the narrow‐lane ambiguity residuals are distributed after ionosphere‐free combined FCB products correction. 96.7% of the wide‐lane ambiguity residuals and 97.7% of the narrow ‐ lane ambiguity residuals are distributed after uncombined FCB products correction. Results: The experimental results show that the positioning accuracy of the proposed method is improved by 25.0% and the convergence time is shortened by 21.1% in static condition, 26.7% and 17.9% in dynamic condition, respectively.Conclusions: Compared with the traditional FCB method, the proposed method can improve the positioning accuracy and shorten the convergence time, which can further broaden the application scenarios of PPP. [ABSTRACT FROM AUTHOR]

The uncertainty of distance‐related error of global navigation satellite system is gradually increasing with the increase of distance between the reference stations and the rover station. Therefore, the dual ‐sys‐ tems of global positioning system (GPS) and BeiDou satellite navigation system (BDS) network real ‐ time kinematic (RTK) method was presented to meet the demand of high‐precision long range positioning RTK. Firstly, the wide‐lane ambiguities were fixed by the multi‐frequency observation data of GPS and BDS be‐ tween long‐range reference stations. The satellite clock errors can be eliminated by the double‐difference so‐ lution model, simultaneously the atmospheric error and satellite orbit errors can be weakened. Then the double ‐ difference carrier phase integer ambiguities can be fixed by the resolution model including atmo‐ spheric error and carrier phase ambiguity. The method of classification error corrections between long‐range reference stations network was used. The observation errors were classified, according to the characteris‐ tics of observation errors between long‐range reference station network. The ionosphere errors and non‐dis‐ persive errors of the rover station were calculated by using the reference stations’error correction and regional error interpolation. The atmospheric errors and satellite orbit errors of the rover station can be weakened by the method of interpolation. Then the errors of GPS/BDS carrier phase observation of the rover station were removed by the calculation errors. The carrier phase integer ambiguities of the rover station can be fixed by the method of resolution integer ambiguity with multi ‐frequency carrier phase, and the position of the rover station was obtained by the fixed ambiguities. The algorithm validation was carried out by the data on long ‐ range reference station network. Three long ‐ range reference stations and one rover station were used to test in Central China. The positioning accuracy of centimeter can be obtained by the algorithm of du‐ al ‐ systems of GPS and BDS network RTK. At the same time, single system can also get the centimeter level of position and the GPS is better than BDS. The method of dual ‐systems of GPS and BDS network RTK can guarantee the positioning accuracy of the rover station. The results of experiment indicate that the GPS/BDS long ‐ range network RTK can be realized and the centimeter level positioning accuracy can be achieved by this algorithm. [ABSTRACT FROM AUTHOR]

In view of the problem that the JPDA algorithm can only track the known number of targets and association ambiguity, simultaneously, the number of hypotheses in MHT algorithm increases exponentially over time. This paper proposed a measurement-oriented m-optimal hypothesis N-scan MITT algorithm. Firstly, it used the method of generating m-optimal hypothesis to generate a specified number of optimal and sub-optimal hypothesis in each frame,and used fixed-value N of hypothesis tree depth to generate optimal feasible hypothesis to complete data association. This paper used two-point difference linear method and global least squares estimation to solve the track initiation of single new target and multiple new targets, respectively. The simulation results show that, comparing with MITT-DAM algorithm, the proposed method achieves a balance between tracking performance and operation time. [ABSTRACT FROM AUTHOR]

The blocking approach ignored the weight of block keys and ambiguity between blocking keys,leading to low accuracy. This paper proposed a schema-agnostic entity resolution method based on undirected weighted graph. The method extracted attributes from data sources,combined attribute information entropy and TF-IDF to get clustering attributes and established an unified block scheme. Through the relationship between clustering attribute weight and block key, it gave each group of block key a certain weight. The weight and the cooccurrence frequency of the edge were multiplied and weighted to form the undirected block weighted graph. Finally, it used the pruning scheme to prune the edges. The problem of multi-attribute and block key ambiguity in data was solved and increased accuracy. Experiments on seven real data sets show that the method is effective and scalable. [ABSTRACT FROM AUTHOR]

The concept of place plays an important role for coupling between human behaviors and geo⁃ graphic environments, and thus provides a human ⁃centric research perspective for geographical analysis. In early place studies, it was difficult to capture and represent the comprehensive semantics of a place in com⁃ puter systems due to the inherent vagueness, uncertainty, and ambiguity of places, as well as the high cost of obtaining place⁃based behavioral data at the individual level. Recently, multi⁃sourced big geo⁃data and ar⁃ tificial intelligent methods have brought new opportunities for place modeling and sensing. Moreover, place modeling is an important component of knowledge representation in GeoAI. This article reviews the prog⁃ ress of two directions of place modeling and place sensing. Place modeling aims to construct a platial knowledge model that is more in line with human spatial cognition and communication, so as to improve the intelligence and human ⁃computer interaction of geographical information retrieval and spatial query an⁃ swering. Place sensing aims to capture human perception and cognition about a place to better understand the intrinsic connections between human activities and the geographic environments, and to represent the rich geographical context of a place. The ultimate objective is to construct “white ⁃ box” place ⁃ based knowledge representation and reasoning for promoting the development of GeoAI. [ABSTRACT FROM AUTHOR]

In order to improve the performance of frame disambiguation model, this paper used a neural network model to learn frame representation based on sentences in corpus different from the traditional classification algorithm extracting features manually, and employed the learned frame representation on the frame disambiguation task, which significantly improved the performance of the task. Making full use of the CFN example sentence database and being based on the hinge-loss neural network, the algorithm learnt the frame representation that could distinguish the correct frame from the error frame in the largest degree. This paper also used the WSABIE algorithm to learn the representation vector of the context of the target word, and finally used the cosine distance between the context representation vector and the frame representation vector to make a decision for the task. Experiment performed three sets of two-fold cross-validation (3 x 2 BCV) on 88 ambiguous words in CFN, and the best accuracy of frame disambiguation reach to 72. 52%. The t-test results show that the performance of the proposed method is significantly higher than other frame disambiguation methods. [ABSTRACT FROM AUTHOR]

Objective: The uncertainty of influencing factors of BDS positioning is great in the disaster environment and emergency scene. The applicability and maneuverability of receiver in disaster emergency environment may not meet the needs of positioning. Therefore, the method of augmented positioning between long range stations on smart device was researched to meet the demand high-precision positioning in disaster emergency environment. The augmented positioning algorithm is convenient for high efficiency and easy to realize, and the user can use a very flexible data processing method. Methods: The un-difference error corrections between long-range reference stations was used of augmented positioning. The satellite clock error was eliminated and the atmospheric error and satellite orbit error can be weakened by the un-difference error corrections. The augmented positioning of user including pseudo-range, carrier phase and carrier phase smoothing pseudo-range between long range stations were achieved. And the demand of high-precision positioning of long range was meted by corrections of classified errors. The method of carrier phase smoothing pseudo-range by un-difference error corrections was used. The integer ambiguity was estimated by observations with eliminating errors and the pseudo-range was recalculated by the simple smoothing formula. The user station errors were removed or corrected by the reference station smoothing error corrections.The pseudo-range observations do not involve ambiguity with simple positioning mode and high- real-time performance, at the same time the accuracy of pseudo-range positioning can be improved by carrier phase observations. And this method can be better applied to the demand for high-precision positioning in disaster environment. The augmented positioning for specific receiver equipment was also integrated in the smart device. Results: Three reference stations between long range together with smart device and receiver in North China were used to test the augmented positioning. The positioning accuracy of dm or cm can be obtained by augmented positioning with pseudo-range and carrier phase smoothing of receiver, the accuracy on cm level obtained with carrier phase. The smart device can get the position on dm level of horizontal with carrier phase smoothing augmented positioning, and the augmented positioning with carrier phase was able to achieve the accuracy on cm level by fixed ambiguity or float ambiguity. The kinematic augmented positioning of smart device can get the positioning accuracy better than 1 meter with the test at Liaoning. Conclusions: The smart device can be used as the source of observation and the carrier of data processing for user receiver positioning. The Results: indicate that the method can achieve high-precision positioning with real-time dynamic centimetre, decimetre and sub-meter levels better than 1 meter. [ABSTRACT FROM AUTHOR]

According to the problem of complex data processing caused by the correlation between stations and satellites in the double-difference network RTK(real-time kinematic), an algorithm of BDS un-difference network RTK with triple-frequency is proposed. Firstly, the integer linear relationship among extra-widelane, wide-lane and triple-frequency integer ambiguity is used to determine double-difference integer ambiguity between BDS network RTK reference stations. Then, according to the composition relationship between double-difference and un-difference integer ambiguity, un-difference integer ambiguity between reference stations is quickly determined at single epoch. On this basis, a high-precision region error correction model of BDS un-difference is established to realize the error correction and integer ambiguity fixing of use. This algorithm is tested by the measured triple-frequency data of BDS CORS(continuously operating reference stations) network. The results indicate that the algorithm of un-difference network RTK with triple-frequency can effectively overcome the correlation between station and satellite which is brought by the double-difference network RTK and make the operating type of the network RTK more flexible. [ABSTRACT FROM AUTHOR]

The experimental satellites of BeiDou global navigation satellite system (BDS‐3) broadcast new B1C / B2a / B2b signals that overlap with GPS L1/L5 signals and European Galileo E1/E5a/E5b signals, which provides the opportunity of tightly combined relative positioning for short baselines with observations from GPS, Galileo, and BDS ‐ 3 experimental satellites. In this contribution， we first evaluate the value and time‐domain stability of differential inter‐system bias (DISB) between overlapping frequencies of GPS, Galileo, and BDS ‐ 3. The results show that the DISB of the same type of receiver is close to 0, and its influence can be ignored in the tightly combined relative positioning. Then we preliminarily evaluated performance of single‐epoch tightly combined relative positioning for short baselines with observations from GPS， Galileo， and BDS‐3 experimental satellites. The results show that, compared with the traditional loosely combined model, the tightly combined model can significantly improve the success rate and reliability of ambiguity resolution. The improvement is especially significant (approximately 25% ‐45%) under environments where the observed satellites for each system are limited and only single‐frequency observations are available. [ABSTRACT FROM AUTHOR]

The satellite Fengyun 3C(FY3C) launched in 2013 and carried a global navigation satellite system (GNSS) occultation sounder, which is the first BDS/GPS compatible radio occultation sounder in the world and records both GPS and BDS measurements. It provides an opportunity for investigating the precision realtime orbit determination based on space‐borne GPS/BDS measurements. In order to realize the real‐time orbit determination based on space‐borne GPS/BDS measurements with decimeter‐level accuracy, this paper carries out in‐depth research in the following aspects. Firstly, the real‐time orbit determination mathematical model based on the space‐borne GPS/BDS carrier phase observations is introduced. Then the properties of the errors in the signal’s propagation path that originates from GPS/BDS broadcast ephemeris are analyzed, and the signal‐in ‐propagation path error(SIPPE) statistics of different kinds of GPS/BDS satellites are also presented. Based on the analysis, a pseudo‐ambiguity is modeled as a stochastic process and estimated in the real‐time orbit determmination(RTOD) filter to absorb the SIPPE error, and then the decimeter‐ level accuracy can be realized. The space‐borne GPS/BDS data from China’ s FY3C satellite are em ‐ ployed for the simulative RTOD test using the SATODS software. Results have demonstrated that the position and velocity accuracy of 30 cm and 0.3 mm/s, respectively, are achieved when using GPS/BDS carrierphase data and broadcast ephemeris. Although the accuracy of BDS broadcast ephemeris is obviously worse than that of GPS, orbit results of the GPS/BDS fusion solution with reasonable stochastic models for pseudo‐ambiguities will be slightly superior to that using single GPS data. For example, when the FY3C satellite flew over Asia/Pacific region where more BDS satellites can be tracked, the orbit accuracy can be improved by 10% with the GPS/BDS fusion solution. [ABSTRACT FROM AUTHOR]

Traditional digital image restoration methods produce errors in the relative displacement between the camera and the subject during the actual shooting exposure time, resulting in poor restoration results. A lossless restoration method based on ambiguity parameter estimation is proposed. An ambiguity image degradation model is built to measure the relative motion direction and horizontal direction angle in the spectrum, estimate the motion ambiguity direction, and the motion ambiguity parameter by using the space Cartesian coordinate system. Through the radial basis function neural network structure, the input function is calculated, and the relative displacement of the camera and the shooting object during the actual shooting exposure time is compared with the estimated result, and the ambiguity error is calculated. Wiener filter restoration method is used to design the restoration process and realize the lossless restoration of digital media images. According to the experimental results, the fault tolerance of ambiguity direction of the proposed method is controlled within 1°, the fault tolerance of ambiguity degree is controlled within 0.2, and the improvement percentage of ambiguity degree is more than 40%. The restored images are relatively clear. [ABSTRACT FROM AUTHOR]

It’s important to find an orthogonal set of transmitting waveforms of MIMO sonar, and the orthogonality of signal set has a direct affect on the detection efficiency of MIMO sonar. The frequency-hopped signal based on a Costas sequence has a nearly ideal range-Doppler ambiguity function, however, the different frequency-hopped signals constructed by different primitive elements of a finite field are not always orthogonal. A search method for primitive elements is proposed based on the finite field theory, and an optimal orthogonal set of transmitting waveforms is designed based on the primitive elements of safe primes. The simulated results show that a set of transmitting waveforms made from a safe prime, which is less than 1 000, has not only the best orthogonality but also the maximum number of signals. [ABSTRACT FROM AUTHOR]

Combining the randomness and ambiguity of the cloud model in precise values and the characteristics of fast generation of third-order Fibonacci sequences. A pseudo-random sequence generator of chaotic system combining cloud model with generalized third-order Fibonacci is proposed. Firstly, the chaotic sequence generated by the quantum logistic chaotic system is used as the parameter of the generalized third-order Fibonacci function model to achieve the dynamic randomness of the parameters, then the cloud droplet group generated by the cloud generator is used as the variable of the generalized third-order Fibonacci function, and then the generalized third-order Fibonacci function is coupled with the Logistic map to obtain the generalized third-order Fibonacci chaotic system model. Based on this model, a pseudo-random sequence generator is designed. The experimental simulation analysis shows that the generator can generate chaotic pseudo-random sequences quickly and in parallel form, and has the characteristics of simple structure, strong pseudo-randomness, uniform distribution and low correlation. In each time the chaotic pseudo-random sequence generated has independent randomness, and the periodicity cannot be found, thus, the fundamental defects in the design of chaotic pseudo-random sequence generator are overcome. [ABSTRACT FROM AUTHOR]

In the production process of enterprises, there are many factors that affect unsafe behavior. Tolerance of ambiguity as a personality trait will also affect employees’ unsafe behavior. Reducing the occurrence of unsafe behavior of employees can guarantee the personal safety of employees. By studying the relevant literature, three categories of influencing factors and 12 sub-factors on tolerance of ambiguity are condensed. The analytic hierarchy process (AHP) and the decision-making test and evaluation laboratory (DEMATEL) are used to calculate the influence degree of each influencing factor of tolerance of ambiguity. The results show that the way of thinking, learning ability, observation ability, problem solving, avoidance uncertain situations, have deeper impact on employees’ fuzzy tolerance levels, the comprehensive influence of the way of thinking reaches 0.2788, so it is the main cause of fuzzy tolerance. Relevant departments can proceed from these five factors and actively to take measures to intervene in tolerance of ambiguity. [ABSTRACT FROM AUTHOR]

Frequency division multiplexing of GLONASS signals causes inter - frequency bias(IFB) in the receiving equipment. IFB significantly prevents GLONASS ambiguity resolution and limits the accuracy and reliability of GLONASS positioning and orbit determination. Therefore, we present a new method for GLONASS ambiguity resolution. Firsly, it weakens the influence of inter-frequency code bias, and wide-lane ambiguities are calculated directly based on the wide-lane combined observations. Then, according to the range of inter-frequency phase bias rate, a step-by-step search schedule is designed to remove the impacts of inter-frequency phase bias on wide-lane and narrow-lane ambiguities. Finally, the ambiguity resolution can be achieved successfully. An IGS experiment network is carried out to verify the validity of this method. Experimental results show that the maximum, minimum and mean success rate of fixed ambiguities within the month were 95.4%, 88.8% and 93.45%, respectively. After ambiguity resolution, the repeatability and root mean square error (RMSE) of N, E, U components were improved; especially for E component, the repeatability and RMSE were improved 20% and 14%, respectively. This proves the validity of this method. [ABSTRACT FROM AUTHOR]

Single-frequency GPS ambiguity resolution on-the-fly has the problem that normal equation is ill-posed. Using epoch-differenced coordinate information between neighboring epochs can mitigate the ill-condition problem to some extent, as a result, the accuracy of the float ambiguity solution will be improved and the convergence time of ambiguity will be shortened. In order to further improve the ambiguity fixing effciency of epoch-differenced method, the epoch-differenced coordinate pseudo-observation error equation and its new variance matrix is reconstructed. The experimental results show that, compared with the previous algorithm with epoch-differenced coordinate information, the new method has higher stability and efficiency. [ABSTRACT FROM AUTHOR]

In view of the minimum variance distortionless response( MVDR) algorithm of acoustic vector array, an improved acoustic vector array MVDR azimuth estimation method( IAVAMVDR) is proposed in consideration of the angle resolution and the single side pointing characteristic. The MVDR characteristics of traditional acoustic vector array are analyzed from two aspects of space power and subspace decomposition. The two covariance matrix construction methods are introduced by using the analytic velocity structure and the acoustic pressure-vibration velocity to suppress isotropic noise. On this basis, the target azimuth estimation is realized. The theoretical analysis shows that IAVAMVDR algorithm is used to effectively reduce the influence of signal subspace, making the main lobe narrower and the side lobe lower, and has ability of suppressing left-right ambiguity. The simulated and measured data prove the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]