25 February 2016, Volume 36 Issue 3
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jgg. 2016, 36(3): 189-192.
Abstract: This paper aims at exploring the algorithm of g7 by processing the data from FG5 and A10 absolute gravimeters. When the observation equation and algorithm offered by the the software user manual is used to process the A10 data, the difference between the results of the designed program and the g7 software is less than 3 μGal. However, for the FG5 data, the difference is too large to accept. After correcting the observation equation and time observations, the latter is within －0.1—0.1 μGal. We believe that the models and algorithms mentioned in this paper are same as those used in the g7 software.
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jgg. 2016, 36(3): 193-197.
The divergence and instability of the Euler deconvolution’s solution is always a restricting factor in its application. This paper introduces some feasible improved methods such as using gravity vertical gradient for inversion, using the excluding criterion and calculating the signal extremum area for inversion. We test their inversion effects compared with the conventional method in a model experiment. The results show that these improved methods can obviously improve the accuracy and convergence of the solutions.
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jgg. 2016, 36(3): 198-201.
In order to build a navigable high-precision gravity reference map efficiently, it is indispensable to improve the precision of the interpolation algorithm, and take its optimization into account. In view of the difficulty of optimizing an efficient interpolation algorithm for gravity reference maps in the various interpolation algorithms, a interpolation optimization algorithm for gravity reference maps in local anomaly fields is put forward. This algorithm realizes preliminary optimizing of the different algorithms by studying long-term data interpolation, determining the weight by means of an analytic hierarchy process, and defining quantitative coefficients of the optimization algorithm (named optimizing degrees). The experimental results show that the optimization algorithm is operational and that the time to interpolate a gravity reference map is reduced in special conditions.
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jgg. 2016, 36(3): 202-205.
Waveform modification provides a possibility to further improve the quality of coastal altimetry data. Using the Jason-1 SGDR data, the shortcoming of Tseng’s modification method is pointed out. We propose an improved modification algorithm by revising the strategy of selecting reference waveforms and determining weights for amending outliers. Test results show the improved method can avoid the deformation of waveform leading edge caused by Tseng’s method, and effectively increases the precision of coastal sea surface heights.
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jgg. 2016, 36(3): 206-210.
We discuss the differences between, and applicability of, diverse global ocean tide models, such as NAO99b, FES2004, GOT4.7, TPXO7.2 and EOT11a, with respect to their adoption in the China area. Characteristics of deformation induced from the ocean tide loading in China GPS sites are analyzed on the foundation of the Global and high accurate local ocean tide models. GPS data from numerous field observations in China are processed by using GIPSY software, based on the two ocean tide model (with and without local ocean model) in order to analyze the influence of the high accurate local ocean tide on Chinese coastal GPS position time series. The results show that: this method can have an influence on the position, which can get to 5.01 mm in the vertical component, and may effectively induce false nominal signals with periods of 15 d and 173 d, without considering the deformation induced from local ocean tide in high data processing.
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jgg. 2016, 36(3): 211-215.
The principles of and differences between Beidou single-system and multi-system zero-difference precise orbit determination are presented. Their respective precision is compared based on real observation data. The results show that the precision of two methods is comparable in current conditions. The three-dimension orbit precision of GEO can reach about 1 m, and that of IGSO and MEO can reach 0.2—0.3 m. Their radial precision is better than 10 cm.
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jgg. 2016, 36(3): 216-220.
Based on the theory and method of dynamic orbit determination, the calculation method of MDOP value of dynamic parameters is given in this paper. Subsequently, the MDOP value of dynamic parameters is considered as the standard to analyze the contribution of different tracking station distribution schemes and different tracking station construction schemes for BDS orbit determination. Finally, the conclusion is verified by the BDS orbit determination. The results show that the correspondence relationship between the MDOP value of dynamic parameters and the precision of orbit determination is obvious. It can be considered the optimally selected basis of the tracking station distribution scheme.
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jgg. 2016, 36(3): 221-225.
We propose a new method called differential positioning based on grid virtual reference stations to improve the security of the coordinates of the national geodetic control points. In this method, we select the points intersected by the longitude and latitude as the virtual reference stations, integrate pseudo-range correction of the virtual reference stations by the physical reference stations, broadcast the coordinates and the pseudo-range correction of the virtual reference stations, and calculate the users’ positions. Experimental results show that the new method achieves accuracy to the decimeter-level, which is almost equal to the pseudo-range differential positioning based on multiple reference stations.
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jgg. 2016, 36(3): 226-228.
The basic principle of the least squares collocation is expounded and the solutions are given under the conditions in Tikhonov, and a new a priori variance-covariance estimation method is shown. Finally, the influence of signal and noise in the right choice for GPS elevation fitting precision is analyzed through an example. Our research shows that, with the increase of the ratio of signal and noise power, the accuracy of fitting is obviously improved and the accuracy of checking is improved to some extent.
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jgg. 2016, 36(3): 229-234.
The troposphere delay is one of the most important sources of error in GNSS positioning. In this paper, the zenith tropospheric delay measured by water vapor radiometer (WVR) is used to evaluate the performance of four types of widely used troposphere models: Saastamoinen, GPT2, EGNOS and UNB3M, in Shanghai. Furthermore, the troposphere delays obtained from WVR and the four troposphere models are applied in GNSS precise point positioning (PPP). Data processes show that GPT2 shows the best performance in troposphere delay correction, as compared with the other three models; the mean ZHD bias of GPT2 is -0.11 cm with RMS of 0.75 cm; the mean ZWD bias is -2.34 cm with RMS of 7.67 cm. The position accuracy of PPP results from the ZHD and ZWD observed by WVR is improved by 16%, as compared with the conventional PPP model, in which the tropospheric parameter is estimated.
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jgg. 2016, 36(3): 235-238.
Differential code biases (DCB) are major source of errors in computing the total electron content (TEC) of the ionosphere from GPS measurements. Although instrumental satellite bias values are available from various International GPS Service (IGS) analysis centers, receiver biases are provided only for very few GPS stations. Some other methods are needed to solve receiver DCB values for plenty of other GPS stations. In this study, on the basis of the GPS code and phase observations in Jan. 2013 at IGS stations distributed in different latitudes, some effective methods are developed to estimate receiver DCB values for a single GPS station. It is shown that the differences between receiver DCB values estimated and those released by IGS are almost less than 1.5 ns, and monthly averages of the differences are below 1.0 ns for most receiver stations.
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jgg. 2016, 36(3): 239-243.
In order to determine the linear features of cracks with different characteristics and widths, an adaptive searching binary method is proposed. Through intersection operation with block iterative binary results and a morphological process, a more complete and reliable binary result can be obtained. It is demonstrated experimentally that the method can eliminate the influence of bulk defects and get good effect on the linear features of different width cracks.
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jgg. 2016, 36(3): 244-247.
In order to visualize the position of underground unexploded ordnances and guide the explosive ordnance disposal personnel for accurately excavating and removing them, the LTD series ground penetrating radar mounted with 200 and 400 MHz composite antennas is used to test detection of unexploded ordnances, and the sophisticated Kirchhoff migration method of seismic data processing and interpolation algorithm for three-dimensional imaging is applied to process ground penetrating radar data. Experimental results accurately reflect the position of unexploded ordnances, laying the foundation for their successful removal.
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jgg. 2016, 36(3): 248-252.
To meet the low-cost, high-precision and real-time performance needs of the navigation system for loitering munitions, a GPS/SINS tightly coupled navigation algorithm based on inter-satellite time difference carrier phase (TDCP) measurements is presented. Firstly, the dynamic model of GPS/SINS is introduced in a 15 state tightly coupled GPS/INS iterative. Secondly, the measurement model is deduced to process the inter-satellite time difference measurements in the navigation Kalman filter. Finally, simulation and flight trial results are carried out to validate the effectiveness of the TDCP. The results show that TDCP method, compared to conventional tightly coupled integration based on pseudo-range measurement, is better able to provide sub-meter position accuracies as well as mm/s velocity accuracies for the medium-short endurance loitering munitions navigation system.
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jgg. 2016, 36(3): 253-256.
Usually in ill-posed error-in-variable models, only part of columns in the design matrix possess multicollinearity. This is where the model focuses. According to the focus characteristics, the corresponding regularization strategy is made, which can overcome the ill-posed effects and minimize side effects caused by the process of regularization at the same time. We propose target focus regularization as opposed to the ill-posed error-in-variable model. Numerical experiments show the proposed regularized total least-squares solution method performs better than others.
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jgg. 2016, 36(3): 257-260.
In order to choose the most robust estimation methods, observations are simulated by generalized Gaussian distribution (GGD),which can perfectly describe the real distribution of observations. Leveling and trilateration networks with equal weighted and independent observations are taken as examples, and simulation experiments are used to compare the robustness of 12 commonly used robust estimation methods. Our results indicate that when observations obey GGD, the L1, Danish and German-McClure methods, and the IGGⅢ scheme are relatively more efficient robust estimation methods in leveling and trilateration networks with equal weighted and independent observations; this is similar to results in simulation experiments.
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jgg. 2016, 36(3): 261-264.
This paper presents t-type robust estimation of the linear EIV model and EM algorithm. For plane fitting, different numbers of gross errors are added to both in the observation vector and the coefficient matrix. The robust effect of t-type estimation is better, and the deviation between parameters’ mean and true value is smaller by selecting the appropriate degrees of freedom.
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jgg. 2016, 36(3): 265-269.
This paper studies the building method and achievements of the global plate boundary model NNR-MORVEL56, and the differences between it and NNR-NUVEL1A, with respect to the plate relative angular rate and root-mean-square of the rate (RMS). It then discusses the influence in angular rate of the 31 small plates from PB2002 on the other 25 major plates. Mean while, based on the NNR- MORVEL56 boundary, the paper establishes the measurement model by using the latest and most comprehensive global space geodesy measurement data, and it analyzes the correlation with NNR-MORVEL56 to test the rationality of the plate division of the model MORVEL56. Aiming at the complicated characteristics of geological structure in China, this paper puts forward some advice referring to the NNR-MORVEL56 boundary dividing method.
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jgg. 2016, 36(3): 270-273.
With methods such as polynomial interpolation, trend fitting, fast Fourier transformation and robust least squares estimation, the mathematical model parameters of observations can be calculated. Using this mathematical model, the trend, periodicity and abnormal residuals are analyzed. Through the analysis, conclusions are drawn that the main reason for the change of ground tilt value is the accumulation and release of internal stress, and the cause of cyclical variation is periodic gravitation and external environmental conditions. In addition, there will be some chance of an earthquake after successive residual outliers, and the longer an outlier lasts, the higher the probability of earthquakes. With the increase of continuous outliers, the earthquake magnitude correspondingly increases.
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jgg. 2016, 36(3): 274-277.
For mobile deformation monitoring of existing level survey, GNSS observation and gravimetry, dynamic information management has been developed. It can provide monitoring task register, task management and implementation, inspection and acceptance query application data, etc. The team reports survey status to the system via SMS, to improve the management of measurement processes, observing and recording the formation history of the system of observation points or lines of operation. For the follow-up, tasks quickly design and analyze data to provide historical information, advancing mobile measurement toward standardized and systematic models, improving the business efficiency of scientific monitoring. In this paper, using existing standards for monitoring the flow deformation, GNSS and gravity, we design and develop a monitoring mission from the flow design, management and implementation of the data inspection and acceptance, and dynamic information management systems, such as data query functions. The system uses an electronic map (e-map) and a list of ways to design measuring tasks. Work group management reports the job situation via SMS, the system records the implementation process for each measurement task, which further records observation history. This contributes to mission design and analysis of historical data to provide information on the flow monitoring toward standardized, systematic efficient utilization of data flow monitoring services.
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jgg. 2016, 36(3): 278-282.
In this paper, we conduct analysis of signal amplitude-frequency characteristics of strong seismic waves. Based on this analysis, sinusoidal strong seismic waves are generated by a GNSS signal simulator. Moreover, the performance of high-rate (50 Hz) GNSS observations collected by two GNSS receivers (Trimble Net-R9 and NovAtel OEM628) are evaluated from the aspects of raw carrier phase observations and positioning results, respectively. The results show a significant error in both carrier phase and positioning results, in the case of high-frequency motion. Furthermore, the measuring accuracy of two GNSS receivers, especially the Trimble Net-R9, deteriorates with the increase of the frequency of sinusoidal seismic wave.
