In this paper, we analyze the effects on the gravity model from inter-satellite ranging sensor, accelerometer and GNSS receiver errors. The results indicate that range-rate, non-gravity and position need to be surveyed with the accuracy 10-30 nm/s, (1-5)×10-11 m/s2  and 2-3 cm respectively. The accuracy of the gravity model recovered will be 1-2 mGal with 100 km space resolution. The conclusions are useful for developing the next-generation satellite gravimetry mission.

This paper proposes an approach to evaluating earth gravitational models (EGM) based on Gauss-Listing classic geoid definition. The classic geoid is defined as an equigeopotential surface. Using this characteristic, we select a geoid as reference surface, then calculate the gravity potentials of different EGMs on the surface, and build an index of gravity potential standard deviation to evaluate EGMs. The goal is to evaluate the theoretical compliance ability of different EGMs and the same EGM applied in different areas of the earth. The results show that the geoid precision of EGM96 and OSU91A are respectively ±11.1 cm and ±14.3 cm, which means that the precision of EGM96 is better than former. Further, the geoid precision of EGM2008, and EIGEN-6C4 are respectively ±8.8 cm and ±8.9 cm, which means their precision is similar. This is consistent with existing research conclusions. However, the geoid precisions of EGM2008 and EIGEN-6C4 are respectively ±11.3 cm and ±11.4 cm for a global geoid, which means that the precision of EGM2008 is slightly better than former.

Point mass model is widely used in physical geodesy, but several challenges are faced in achieving high performance when solving linear equations. This paper presents a stratified residual point mass model based on window control, which converts the dense linear equation into sparse format. An 112 896-order sparse linear equation is solved on an ordinary computer. In order to illustrate the practicability of window control method, an experiment is carried out to calculate disturbing gravity at various altitudes. The performance results demonstrate that window control method achieves better precision and efficiency compared with traditional methods and is very well suited for large scale point mass construction.

In this paper, we first collect crustal vertical velocity data from leveling network and cross-fault monitoring since 1970s, crustal horizontal velocity from present GPS measuring, the historical earthquake catalogue, and geological maps in Liupanshan and its adjacent areas. Second, we analyze the features of crust movement in the vertical direction and its implication for tectonic activity. The preliminary results indicate that: 1) The features of long-term vertical crust movement in Liupanshan, including the rising in Liupanshan, west Qinling, Helanshan and the sinking in basins, means that the crustal vertical movements are inherited. 2) Considering the GPS horizontal velocity, the crust is squeezing in areas where it is rising. 3) The GPS horizontal velocity in the west of Liupanshan fault is greater than that in the east, implying that the fault of Liupanshan is blocked and the level of accumulated strain is high. These results together indicate a high risk of future strong earthquakes.

Since its construction in 2006, the Hubei seismic network has generated much seismic waveform data. During eight years from 2007 to 2014 there were 306 earthquakes with magnitude ML≥30 in Hubei province and the neighboring 300 kilometers. We re-measured the near magnitudes, body wave magnitude and surface wave magnitude of 180 of these events. According to analysis the distribution of magnitude deviation frequency, we find that using near magnitudes as speed magnitudes is more applicable in Hubei province.

Using continuous GNSS data from the crustal movement observation network of China, we analyze the accuracy and reliability of campaign GNSS stations, and the impact of time span, observation period and observation days for the site velocity. Our results show that: time span has significant impact on the velocity precision of campaign sites. When the time span is about 16 years and the observation period is 2 years for one campaign, the standard deviation of the differences between the campaign and continuous sites is about 0.1 mm/a for the horizontal component, and 0.3 mm/a for the vertical component. Further, the impact of observation days on the differences is less than 0.15 mm/a for the horizontal component and 0.45 mm/a for the vertical component. Besides, with the given time span and observation days, shortening the observation period could improve the accuracy of the campaign GNSS sites.

Starting from the basic equations of single station timing, we analyze the factors that cause systematic bias of timing results. Combining the specific experiments, the influence of satellite clock error and receiver hardware delay is analyzed and some useful conclusions are obtained. The systematic bias caused by satellite clock error for all stations changes with time. However, the systematic bias associated with results caused by the receiver code bias of various stations differs, depending entirely on the value of the different receiver code biases, so it should be corrected carefully in the timing and time synchronization. However, the receiver hardware delay does not affect the frequency stability of timing results, so there is no need to correct it in frequency transfer.

In precise point positioning, high-precision floating ambiguity is important to ensure that integer carrier phase ambiguities are resolved reliably. However, a convergence time of several tens of minutes is required to obtain high-precision floating ambiguity. In this paper, BDS/GPS/GLONASS combined PPP are carried out to accelerate convergence, and then we use the inter phase clock method to realize the GPS PPP ambiguity fixing. Six MGEX stations are used for the kinematic PPP test. The results show that, first, compared with ambiguity-floating PPP, ambiguity-fixed PPP obtains better positioning accuracy, and the BDS/GPS/GLONASS ambiguity-fixed PPP further improves positioning accuracy. Second, the TTFF (time to first fixed) for GPS ambiguity-fixed is 46.1 min, while only 25.8 min for BDS/GPS/GLONASS ambiguity-fixed, which reduces 44.0%. Third, the ambiguities fixed rate raise from 78.6% to 87.4%, improving nearly nine percentage points.

The pseudo-range multipath extraction formula is derived and the combination coefficients of corresponding observation combinations to extract pseudo-range multipath are calculated. The amplificatory scale of carrier noise is used as the evaluation factor to evaluate the effect of extracting pseudo-range multipath. Then the BDS and GPS data are used to validate these analyses. Finally, these conclusions are drawn: when only correcting the first-order ionospheric error, the extraction effect of triple-frequency pseudo-range/carrier phase observation combination is best. Although the carrier noise is excessively amplified based on triple-frequency second-order ionospheric correction, ionospheric system error is eliminated. When extracting the pseudo-range multipath by dual-frequency combination, the effect of the combination with the largest frequency difference is best; when the same observation is used to extract different pseudo-range multipaths, the pseudo-range multipath on the signal with the largest frequency is best.

Due to the presence of inter-channel bias, users of heterogeneous BDS and GLONASS receiver pairs in differential positioning mode will experience ambiguity fixing challenges. In order to improve the success rate of ambiguity resolution, the bias needs to be corrected. This paper proposes an effective algorithm that can estimate carrier phase and code inter-channel biases by a zero baseline. Then, both GLONASS carrier phase and code observations are corrected accordingly in short baseline RTK positioning. The results show that the success rate of ambiguity resolution can be improved significantly.

In order to solve the problem that the full physical experiment of BDS/MEMS IMU deep integration navigation is difficult, a simulation analysis method based on software receiver for BDS/MEMS IMU deep integration navigation system is proposed, which are convenient for evaluation and validation of BDS/MEMS IMU deep integrated navigation performance.The structure of BDS software receiver is given, the deep integration navigation structure and filtering algorithm are introduced.Finally based on the simulation date to verify the analysis.Simulation shows that the deep integration system can improve the navigation accuracy greatly compared with tight integration system, with the position error less than 1 m and velocity error less than 0.01 m/s.

This paper analyses the satellite clock correction principle of parameters with respect to GPS space-time reference points and deduces the BDS differential code bias (DCB) correction formula of single-frequency and dual-frequency ionospheric free combination in standard point position (SPP) and precise point position (PPP). With DCB files distributed by a multi-GNSS experiment (MGEX), some observation stations are calculated both in SPP and PPP. The results of BDS B1B3 and B1B2 dual-frequency SPP show that E direction improvement accuracy is at the sub-meter level, while N, U direction improvement accuracy are at the meter level. Moreover, before correction the position accuracy is extremely poor, with poorer accuracy of dual-frequency positioning compared to single-frequency positioning in E, N direction. From the results in BDS precise positioning, solutions in B1B3, in combination with DCB corrections, are very consistent with the B1B2 combination, and accuracy is improved in static and kinematic modes.

As the satellite’s running state is described by broadcast ephemeris, it thus ensures the user’s real-time navigation and positioning service. In this paper, the orbital and clock parameters extracted from the broadcast ephemeris, which include satellite orbit plane, shape, orientation parameters and satellite clock sequence, are used to analyze Beidou on-orbit satellite’s operation state at the present stage. The multi-results show that anomalies often occur in satellite orbit clock; in addition, the highest frequency anomalies occur in BDS GEO satellite, while the IGSO satellite keeps the middle level, and the MEO satellite maintains the most stable operation.

In this paper, we study a method of cycle-slip detection and ambiguity resolution for Beidou single epoch dynamic baseline solutions, and compile relevant software. We get the measured data from one middle latitude city and then analyze the inner precision and outer precision of the algorithm, calculating short baseline. Results show that north-south direction accuracy is better than 7 mm, east-west direction accuracy better than 5 mm, elevation direction accuracy better than 15 mm; the outer location precision is better than 5 mm.

Nowadays ground-based global navigation satellite system (GNSS) stations of the international GNSS service (IGS) are distributed unevenly around the world，especially in the southern ocean area. As a result, many unreasonable negative vertical total electron content (VTEC) values appeared in corresponding areas referred above. To completely eliminate non-physical negative values, a new method, temporarily named SGG, with IGS’s final VTEC products is proposed for constraining the area where no real data is available, and then we process the GNSS dual data of more than 200 IGS reference station in 2014(high solar activity year) with GIM constraint to validate the new method. The results have shown that the RMS of ionospheric TEC at contributed stations is within 3 TECu in the spatial domain(the RMS over the equatorial anomaly area is approximately 5-7 TECu). Meanwhile SGG efficiently eliminates the unwanted behavior of negative VTEC values in ocean and middle-high latitude areas of the southern hemisphere(40°-90°S), and the original positive VTEC almost won’t be affected(the variation of VTEC can be controlled within 2 TECu).The satellite and receiver DCB of SGG is also highly consistent with IAACs, the RMS and MEAN of satellite DCB between SGG, UPC, ESA, JPL and CODE is within 0.2 ns and 0.04 ns respectively. The receiver DCB valuation changes between SGG and CODE at different latitudes are basically identical(the difference is about 0-1 ns).

Using 14 days’ ionospheric TEC grid data provided by IGS center with different longitude and latitude at quiet and active period, taking the former 8 days’ TEC value as sample data, the prediction models of ionospheric TEC are set up using Holt-Winters additive and multiplicative model respectively. Afterwards, the established models are used to forecast the latter 6 days’ TEC value. The experimental results show that the prediction results of the two models are approximately the same and match well with the observation data, whether in ionospheric quiet or active periods. However, the Holt-Winters additive model can better reflect the changing characteristics of ionospheric TEC.

In this paper, a new station selection method is proposed based on the triangulated irregular network(TIN) topology. This method is used to study the precise orbit determination accuracy, efficiency and station saturation point. The experimental data shows that: when under conditions of the global distribution network, 70 stations can succeed in precise orbit determination with precision better than 3 cm, while computational efficiency is increased by 2 times compared to 140 stations. When the number of stations reaches 90, the precision lifting slows. Ensuring orbit determination precision to establish suitable monitoring stations has importance on the global monitoring network construction of the Beidou navigation system.

In this paper, to solve the parameter of the three-dimensional spatial coordinate transformation model, quaternion is introduced to construct a rotation matrix. This paper proves that the coordinate transformation rotation matrix is equivalent to the orthogonal transformation of quaternion. Using unit quaternion theory derivates a direct algorithm for solving spatial coordinate transformations. A simulation test using analogue data and numerical examples show that the method is feasible and simple, does need not linearization, and can adapt to arbitrary rotation angle rotation transformations.

The dynamic Allan variance (DAVAR) is a new method to analyze the random error of output signals. However, it has defects such as poor confidence on the estimate and great estimation error, due to the reduced amount and freedom of data captured by the window. To solve this problem, a dynamic total variance approach is proposed to track variations in the signal and reduce estimate error. Firstly, we truncate the original signal with a fixed window by fixed step. Then, the data in the windows is extended by an inverted mirror mapping method to improve the confidence level. Finally, the Allan variance values of the extended data are calculated and expressed by two or three-dimensional figures. Simulation data shows that the dynamic total variance approach can track the dynamic variety of signals quickly, and also overcomes the problem of low confidence level and high estimate error.

This paper focuses on the study of scattering properties. Based on the ocean GPS scattering model, a bare soil GPS scattering model is established. Considering the bistatic radar cross section, a random roughness scattering model is employed. After the modification, the effects of soil parameters (soil moisture and surface roughness) on delay Doppler map at different polarizations are simulated. This theoretical study is helpful for the interpretation of data from airborne/spaceborne GNSS-R receivers, experimental design and the inversion algorithm development. At the same time, the results of the delay Doppler map model can also provide a theoretical basis for the study of GNSS+R soil moisture remote sensing.

This paper presents an efficient method, based on integrative clustering filtering (ICF), for an accurate terrain assessment in complex areas. Firstly, the point cloud data is described as the Octree index structure, and then segmented based on planarity. Then a coarse spatial clustering process, based on dual distance is implemented. Secondly, a triangulated irregular network (TIN) is built based on the classic progressive densification method, and the rest of the valid point clouds are classified iteratively. Finally, the experimental results show that the ICF method proposed in this paper is capable of producing reliable DTMs in the discontinuous areas, and all of the above contribute to improving the reliability of the filtering result.

There is a large amount of raw data for high-speed railway ballastless track static detection, and gross errors appeared in them. Based on research into common detection methods, a new method is proposed. This method uses wavelet analysis theory to select the appropriate wavelet basis, and then static test data is filtered to remove the gross errors in raw data of track static detection. Finally, the static detection of Guiyang-Guangzhou high-speed railway is carried out. The results show that the proposed method can effectively remove gross errors, and obtains a good detection effect.

In order to improve the accuracy of MEMS gyro and to meet wide application requirements, an automatic regressive model (AR model) and output model of single MEMS gyro are established. Based on the two models, the state space equation and measurement equation of virtual gyroscope are found. A Kalman filter to combine outputs of gyro array is designed, and to enhance real-time ability, a novel Kalman filter is also constructed. Constant-rate and angular vibration experiments are carried out to verify the validity of the data-combining approach. The results indicate that relative to single gyro, the virtual gyro’s accuracy can increase 18.18 times in the constant-rate experiment and 5.36 times in the angular vibration experiment.

Using GPS, we monitor a landslide in Lixian, Sichuan. Over a year’s monitoring indicates that this mountain is indeed sliding slowly, and the major direction of the slippage is pointing to the school next to the mountain. The displacement of the three monitoring points in this major direction are 180 mm, 262 mm and 448 mm. By gathering the rainfall data in the same time, the comparison indicates that rainfall has a direct effect on the landslide and that it is a delayed effect. We perform a numerical simulation of the process of the landslide using ANSYS, and calculate the displacements of the monitor points. The simulation and monitor results are nearly identical. We derive the relationship between rainfall and elasticity modulus, density, cohesion, internal friction angle, which can be used as a method of landslide prediction.