BeiDou Navigation Satellite System
Geomatics and Information Science of Wuhan University,2018,Vol 43,No. 04
【Abstract】 Aiming at the acquisition problem brought by NH code in the signal of BD2 which leads to sensitivity reduction problem by traditional acquisition methods, this paper presents a weak BD2 signal acquisition method based on adaptive stochastic resonance algorithm. By combining the DBZP method with adaptive stochastic resonance algorithm, the method can eliminate the data hopping and NH hopping, and significantly improve the signal-to-noise ratio. The method can be adopted to achieve the fast signal acquisition with high sensitivity characteristic. The simulation and test results verify that, this method provides stronger capacity of acquainting BD2 signal, has more advantages in real-time, high sensitivity and has a higher application value.
Science of Surveying and Mapping,2018,Vol 43,No. 03
【Abstract】 In this paper, the RTCM 10403.2, which is introduced by the RTCM committee, was introduced, and its characteristics were introduced. The inner loop algorithm and the CRC algorithm were analyzed emphatically. RTMC 3.2 format, compared to the previous version, increased MSM message group. The most important feature of the data format was using the internal loop, and for the first time supporting the Beidou satellite navigation system. In view of these characteristics, the article systematically designed the encoding and decoding algorithm and wrote the software to be realized. Finally, the encoding and decoding algorithms were experimented respectively. The experimental results showed that the proposed encoding and decoding algorithm and the software can correctly and reliably handle the RTCM 3.2 data format and can be applied in practical GNSS differential positioning.
Geomatics and Information Science of Wuhan University,2018,Vol 43,No. 06
【Abstract】 Presently, most of the errors caused by the B3 frequency, antenna phase center offset are corrected by the satellite clock a0 parameter. The errors caused by the variance of different frequencies are corrected by timing group delay (Tgd) parameter for BeiDou navigation satellite system (BDS) through navigation messaging. In order to improve the broadcast ephemeris, we put forward a satellite antenna phase center offset correction and fitting broadcast ephemeris methods. The two approaches are compared in two ways, including the influence on user ranging error and precise point positioning. The results show that the two methods can correct most errors caused by antenna phase center offset. The correction accuracy of the new method is improved by 76% compared with the method using satellite clock a0 parameter, and the positioning accuracy is improved by 12.5%. Accuracy is not affected by time-space factor. The positioning accuracy when correcting the satellite position before ephemeris fitting is about 38.1% higher than that when the satellite antenna phase center offset is not corrected. The correction of the variance of different frequencies of the antenna phase center by Tgd residuals is analyzed. The results show that the influence is at the mm order, so we can correct the variance by Tgd parameter.
Geomatics and Information Science of Wuhan University,2018,Vol 43,No. 08
【Abstract】 Currently, there are five test satellites of BeiDou Global Satellite Navigation System broadcasting new signals. Quality analysis of test satellite observations is a significant content for the verification of the new signal system. Based on single station measurement of BeiDou test satellites, the code minus phase combination (CC) and multipath combination (MP) are employed to analyze the pseudorange noises and multipath errors of civil signals and Bs signal of the test satellites. The result shows that the pseudorange measurement accuracy of inclined geosynchronous satellite orbit (IGSO) satellite is better than that of the medium earth orbit (MEO) satellite; B2a + b signal has the highest pseudorange measurement accuracy as well as the best anti-multipath performance, while the B1C signal performs the worst in both aspects; the pseudorange measurement accuracy of Bs signal is relatively poor, yet better than that of the B1C signal and a systematic error related to elevation exists in the pseudorange multipath series of Bs signal with its maximum value up to 0.5 m.
Chinese Journal of Scientific Instrument,2018,Vol 39,No. 06
【Abstract】 Global navigation satellite system (GNSS) time comparison is one of the major technologies in the generation of international standard time. Global positioning system (GPS) and global navigation satellite system (GLONASS) have been authorized as the official method by BIPM. To promote the application of Beidou in the realization of international standard time, Beidou common view time comparison is firstly implemented through the pseudo-code measured data among the National Time Service Center, Chinese Academy of Sciences, Technical Research Institutes of Sweden and Royal Observatory of Belgium in the frame of GNSS time comparison standard. Experimental results are summarized as follows. The STDEV of Beidou zero-baseline with common view time transfer is less than 1 ns. The RMS of Asia-Euro long baseline Beidou common view time comparison is better than 2.5 ns. The stability can reach 10 −14 (1 day). This is almost the same level with GPS common view time comparison. It is proved that Beidou can be adopted as the nanosecond level of time transfer or time comparison. The experiment can support that Beidou will be involved as the official method in the calculation of the international standard time in future.
Science of Surveying and Mapping,2019,Vol 44,No. 01
【Abstract】 In view of the uneven distribution of the BeiDou ground reference station, which affects the precision of BeiDou orbit determination, the grid based stochastic optimization method was adopted in this paper. The method took account of factors such as quality, distribution and station stability of the monitoring stations to evenly select the global distribution of MGEX stations. The weighted GDOP index was used to evaluate the effectiveness of the selected stations. And the influence of the number, distribution and quality of the monitoring stations on the orbit determination precision was comprehensively analyzed. The results showed that the precise orbit determination of GEO, IGSO and MEO satellites of BeiDou satellite was 221.56, 12.59 and 6.81 cm, respectively when 30 monitoring stations are selected by this method, there was a greater improvement than the grid method. Within a certain range, the more number of stations indicated the higher precision of orbit determination.
Geomatics and Information Science of Wuhan University,2018,Vol 43,No. 11
【Abstract】 The precise point positioning (PPP) mode has been widely used in many fields, such as vehicle navigation, surveying and mapping, and earthquake monitoring etc. In recent years, multi-GNSS is an obvious trend with the increasing number of satellites. In this paper, BDS/GPS PPP is researched by comparing the calculation of the data from global Multi-GNSS Experiment (MGEX) with BDS and GPS PPP. The results show that the average RMS of BDS static PPP is 4.35 cm, 3.01 cm, 6.40 cm while the average RMS of GPS static PPP is 1.21 cm, 0.48 cm, 1.79 cm in east, north and up directions, respectively. The average RMS of BDS/GPS static PPP is 1.21 cm, 0.50 cm, 1.87 cm in east, north and up directions, respectively. In kinematic PPP, the accuracy of positioning in BDS is better than 10 cm and 15 cm in horizontal and vertical directions respectively. While the accuracy of GPS and BDS/GPS is all better than 5 cm and 8 cm in horizontal and vertical directions, respectively. The number of satellites in BDS/GPS is the double of that in single system. And the spatial structure of combined system is greatly enhanced which can improve the stability of positioning. In addition, whether in static PPP or kinematic PPP, the combined system can greatly shorten the convergence time and reduce jitter compared with single system especially with BDS PPP.
Science of Surveying and Mapping,2018,Vol 43,No. 12
【Abstract】 Aiming at the problem of verifying and analyzing the precision of the earth rotation parameters (ERP) which needs to be determined independently by using BeiDou navigation satellite system (BDS) data in China, this paper used the global positioning system (GPS) reference station data in and around China and the BDS data of MEGX network to calculate the ERP, and the accuracy of the calculation results were compared and analyzed. The calculation results showed that RMS of the difference calculated by BDS data and the International Earth Rotation Service (IERS) was 0.657 6 mas in X direction polar motion, 1.032 4 mas in the Y direction polar motion, and 0.085 3 ms in UT1-UTC; RMS of the difference calculated by GPS data and IERS was 0.451 6 mas in X direction polar motion, 0.547 5 mas in the Y direction polar motion, which was obviously better than that of BDS data, and RMS was 0.215 3 ms in UT1-UTC, which was worse than that of BDS data. Using two techniques to solve the ERP, it was found that there were obvious systematic errors in the pole motion parameters, and there was no obvious systematic error in the UT1-UTC values. The research results showed that using BDS technology to determine the accuracy of the ERP was worse than GPS, but the data accuracy was greatly improved compared with the previous ones.
Science of Surveying and Mapping,2019,Vol 44,No. 02
【Abstract】 In view of the advantage that BeiDou navigation system is the only positioning system that can broadcast the practical triple-frequency signal at present, the merits and demerits of the least-square ambiguity decorrelation adjustment (LAMBDA) method and three carrier ambiguity resolution (TCAR) method were analyzed in this paper. Extra wide lane and wide lane ambiguity that were fixed were functioned as constraint condition for triple-frequency positioning model and narrow lane (NL) ambiguity was fixed by LAMBDA in this paper. It was shown that triple-frequency positioning model with constraint condition promoted the ambiguity resolution (AR) success rate under the case of short length baseline and accelerated ambiguities and coordinate parameter speed compared with traditional triple-frequency positioning model by experiments.
Geomatics and Information Science of Wuhan University,2018,Vol 43,No. 12
【Abstract】 Three kinds of triple-frequency precise point positioning (PPP) models containing two ionosphere-free combined models, the model of triple-frequency ionosphere-free linear combination and uncombined model are achieved based on Trip software. Triple-frequency PPP models and traditional dual-frequency ionosphere-free combined PPP model are tested by BDS data from 12 stations of Crustal Movement Observation Network of China. The results show that for most stations, daily static positioning accuracy is better than 1 cm in horizontal, 2 cm in vertical, and is better than 4 cm in horizontal and 6 cm in vertical for kinematic positioning accuracy. The average convergence time for each triple-frequency is about 120 min for static case and about 180 min for kinematic case. Comparing with traditional dual-frequency PPP models, triple-frequency PPP models can obtain higher accuracy. To be specific, root mean square (RMS) in daily static solutions of triple-frequency uncombined PPP models can be improved by 36.1% and 6.3% horizontally and vertically, and RMS in daily kinematic solutions can be improved by 9.1% and 6.3% horizontally and vertically.
Geomatics and Information Science of Wuhan University,2019,Vol 44,No. 04
【Abstract】 A multi-GNSS precise point positioning (PPP) algorithm considering the inter-system bias (ISB) is adopted to process the multi-GNSS data obtained from seven stations of the multi-GNSS experiment (MGEX). Using the proposed algorithm, the ISBs values can be achieved between Galileo, GLONASS, BDS (BeiDou Navigation Satellite System) and GPS (Global Positioning System). The results of static multi-GNSS PPP solutions show that RMS (root mean squares) values are 8.9 mm, 5.3 mm and 10.9 mm for the east, north and up directions respectively. One-day stabilities of ISBs described by STD (standard deviation) values are better than 0.12 ns for different systems, and especially Galileo is the best one. From the sequence of multi-day ISBs, significantly irregular ISB jumps can be found where the change range can reach nearly 20 ns. There are some differences on ISB values for different types of receivers, and the ISB values are similar for same types of receivers. On the whole, the ISB for Galileo is the most stable and optimal, and the results of BDS and GLONASS are almost equivalent.
Science of Surveying and Mapping,2019,Vol 44,No. 04
【Abstract】 In order to study the effects of the solar radiation pressure model on orbit prediction, the final precise orbit products from August 1, 2017 to November 30, 2017 were adopted, and the effects of different solar radiation pressure on orbit prediction of BeiDou IGSO, MEO satellite and Galileo satellite were studied in this paper. The solar radiation pressure model includes ECOM 5 parameters model, ECOM 9 parameters model and the adjustable Box-wing (A-BOXW) model. The predicted orbits were compared with final precise orbits and satellite laser ranging (SLR) observations, and the residuals were used to evaluate the accuracy of predicted orbits. For BeiDou satellite, the results of ECOM 5 parameter model and ECOM9 parameter model were similar. The A-BOXW model was the worst, but in the radial direction of satellite, the ECOM 9 parameter model was superior to the ECOM 5 parameter model. For the Galileo satellite, the ECOM 9 parameter model was better than the ECOM 5 parameter model as a whole.
Geomatics and Information Science of Wuhan University,2019,Vol 44,No. 02
【Abstract】 Comprehensive zone correction is a new type of differential corrections for BeiDou wide-area augmentation system. As broadcasted together with the equivalent satellite clock (ESC) and orbit corrections by BDS satellites, they enable user decimeter-level real-time positioning capability using the carrier-phase observations. In this paper, we give a brief introduction of comprehensive zone corrections, and the function model of precise point positioning (PPP) for dual-and single-frequency users using the comprehensive zone corrections. Tracking data of 30 stations in mainland China are used to evaluate the PPP performance, including convergence time, positioning accuracy and its relation with the user’s distance from the zone center. Results show that the dual-frequency PPP convergences to 0.5 m in 25 minutes and the positioning accuracy are 0.15 m in horizontal and 0.2 m in vertical, respectively. As for single-frequency PPP, the positioning accuracy convergences to 0.8 m in 20 minutes, while the positioning accuracy is 0.3 m in horizontal and 0.5 m in vertical. We conclude that the BDS PPP accuracy using the broadcasted wide-area differential corrections reaches decimeter-level within the distance of 1 000 km around zone center, and the accuracy becomes slightly worse with the user’s distance from the zone center increasing.
Linear combination optimization model of BeiDou triple-frequency integral coefficient carrier phase observation
Science of Surveying and Mapping,2019,Vol 44,No. 08
【Abstract】 According to the application requirements of BeiDou triple-frequency observation, the linear combination observation model was established. Based on the error analysis of the model, a spatial analysis of the real coefficient ionosphere-free combination, troposphere-free combination, and minimum noise combination weakening or eliminating errors was conducted from a geometric perspective. Then, the relationship between the ionosphere-free plane, the troposphere-free plane, and the minimum noise line was more intuitively described. Upon this basis, the linear combination of the BeiDou integral coefficient was derived, and the combination of long wavelengths, weak ionospheric delay and weak observation noise was analyzed. Moreover, the number of lanes, the ionospheric delay coefficient and the noise amplification factor were used as the judgment indicators for the linear combination of the optimal triple-frequency integral coefficient. Finally, several sets of the linear combination of the optimal triple-frequency integral coefficient with different characteristics represented by (−1, −5, 6), (0, −1, 1), and (1, 4, −5) were obtained, and the sum of the coefficients of the optimized liner combination model of triple-frequency integral coefficient was generally S = 0 or S = ±1.
Geomatics and Information Science of Wuhan University,2019,Vol 44,No. 10
【Abstract】 The BeiDou global navigation system was officially launched in 2017 and will adopt a new BeiDou global ionospheric delay correction model (BDGIM). Using high-precision grid ionospheric data released by CODE and the ionospheric delay derived from dual-frequency observations as a reference, we analyzed and evaluated the accuracy of the BDGIM model and compared it with that of the BeiDou Klobuchar and GPS Klobuchar models. The results show that in the region of China, the BDGIM model and the BeiDou Klobuchar model are comparable in accuracy and superior to the GPS Klobuchar model. On a global scale, the accuracy of the BDGIM model is better than that of the BeiDou Klobuchar and the GPS Klobuchar models. Different ionospheric models are implemented for single point positioning. The results show that the BDGIM model has a 13% improvement over the positioning accuracy of the BeiDou Klobuchar model, and a 7%–10% improvement over the GPS Klobuchar model.
A method for estimating GNSS instrumental biases and its application based on a receiver of multisystem
Chinese Journal of Geophysics,2019,Vol 62,No. 04
【Abstract】 With the development of Global Navigation Satellite Systems (GNSS), the signal from more than 30 satellites of GNSS can be caught by a receiver in China at a time, which will provide conveniences for estimating instrumental biases of GNSS. In this paper, instrumental biases of GNSS have been firstly analyzed under different temperature conditions. The results show that instrumental biases are changed with the rapid change of temperature and the variation of instrumental biases can reach 12.53 total electron content unit (TECU, 1 TECU = 10 16 el·m −2). Furthermore, the change of instrumental biases is slow and about 1.00 TECU at constant or room temperature. Based on the above experiments of instrumental biases, we have proposed a method of estimating GNSS instrumental biases for a receiver of multisystem. The method is named Triangle Decomposition and Difference Elimination (TDDE) method for a single station and applied in analyzing GNSS data in Baoding during 2015–2017. Our analysis shows that TDDE is advanced in speed and independence for solving instrumental biases. The result obtained by TDDE in BeiDou Navigation Satellite System is better than that in GPS and GLONASS. Meanwhile, the instrumental biases corrected by TDDE are 2.50–3.00 TECU larger than those adjusted by Global Ionosphere Maps from the Center for Orbit Determination in Europe. In addition, the vertical TEC corrected by TDDE can clearly present diurnal variation, sunrise enhancement, semi-annual and annual variations, and equinoctial asymmetry of ionospheric TEC.
Instantaneous Prediction of Vehicle Outline Conflict Using High-frequency and High-precision Positioning Information
China Journal of Highway and Transport,2019,Vol 32,No. 06
【Abstract】 The vehicle collision warning system is a key component of advanced driver assistance systems (ADAS), which can effectively reduce the traffic accident rate. The core technology of the vehicle collision warning system involves the detection of distance to a vehicle in front by multiple on-board sensors and the determination of safety indicators. However, owing to its high cost and environmentally sensitive nature, this method is not widely promoted. This paper proposed a novel method based on a BeiDou Navigation Satellite System (BDS), which has recently gained popularity in the field of transportation. First, position information at the centimeter-level was collected by the on-board terminal at a frequency of 5 Hz by using the BDS-based continuously operating reference station (CORS) system built along the highway. Second, a model was proposed to predict the vehicle outline conflict at the target moment. This was demonstrated in a 7 km section of an expressway in Xi’an. From the field experiment, 6 000 samples were collected. The results indicate (1) in a static state, a centimeter precision level is achieved; (2) At speeds of 80–100 km·h −1, a decimeter precision level is attained; (3) The standard deviation of the errors between the actual values and predicted values for the lateral and longitudinal distance can reach up to centimeter-level and decimeter-level respectively. The method proposed in this paper is feasible and extendable because of the high precision of the model.