This reseach compares the correlation between GPS PWV (precipitable water vapor) and PM2.5/PM10 of Beijing in 2013. It is concluded that there is a significantly positive correlation among autumn, winter and spring seasons, in which the correlation coefficient is greater than 0.5 and the best correlation coefficient amouted to 0.89. The correlation is not obvious in summer. The important factor in causing fog and haze weather is the rise of PWV in the autumn, winter and spring seasons.
Based on precipitable water vapor data as received from GPS and weather data from The Hong Kong Observatory in Hong Kong on March 30, 2014, this paper analyzes variations in precipitation over a large area. The results show that heavy rainfall may occur before GPS precipitable peak, and the mutation phenomenon of GPS precipitable may or may not occur before the rain. The complexity of Hong Kong’s terrain is an important factor affecting GPS precipitation variations, as is the effective range of single base stations to obtain the distribution of water vapor. The timing diagrams of GPS precipitable contours can be used to visually analyze water vapor transmission.
We study the prediction performance of several frequently-used methods used for navigation satellite clock bias prediction, including the quadratic polynomial model, the spectral analysis model, the grey model (GM (1,1)), the ARIMA model and the Kalman filtering model. By using the precise SCB data of GPS, the prediction tests are carried out to analyze their prediction results. The advantages and disadvantages of these methods are then compared. In addition, the prediction characters of six-type GPS sapceborne clocks in orbit are roughly analyzed.
The combination of the phase observations between different frequencies is presented, using the Galileo four frequency as an example| and the general form of combination observation in the unit of cycles and meters is given. The ionospheric error, wavelength and the observation noise is analysized in detail. With the integer ambiguity as a prerequisite, some useful linear combination as long wavelength, weak ionospheric delay and weak observation noise is researched. Finally, depending on the combination principle, programming to calculate combination coefficients of different navigation system and several typical combination coefficients are given.
To resolve the challenge of the current contradiction between the demands of large GNSS network data processing and existent processing capabilities and strategies, a new network solution algorithm\|Ambizap\|which is based on fixed point theorem, is introduced in this paper. We then introduce distributed computing technology into GNSS data processing. The distributing processing flow of large GNSS network data based on the Ambizap algorithm is designed and achieved through use of NET framework distributed technology under the distributed environment. The accuracy of the Ambizap algorithm and the efficiency of its distributed application are verified through some examples. The results show that the distributed processing of Ambizap can effectively resolve the contradiction currently faced by large GNSS network data processing, bringing a more efficient and economical processing method.
Corrected by high-order ionospheric delay, observations are used to estimate satellite orbits and clocks. And the other site’s tropospheric delay is calculated by these orbits and clocks. The results show that it is easy to reach 1cm value in the second-order ionosphere at low latitude areas. This can cause 2-3 mm error to troposphere estimation. But the third-order ionosphere estimation typically cannot exceed 5 mm at low latitude areas. A data test implies that if 1 mm precision of troposphere estimation is desirable, then the site’s second-order ionosphere computation must be corrected in middle and low latitude areas. Since the third-order ionosphere computation effect on troposphere estimation is very small, it can be safely neglected.
Singular Spectrum Analysis (SSA) is one method of generalized power spectrum analysis and it is able to identify and enhance signal stability, especially the periodic signal. It therefore has good application in the time series analysis. GPS coordinate series analysis is currently a hot issue. This paper studies GPS coordinate time series denoising and seasonal signal extraction based on SSA. Through analysis of simulation experimental data and GPS measurement data, as well as comparison with empirical mode decomposition (EMD) and wavelet analysis, numerical results show that SSA, EMD and wavelet analysis are effective denoising methods, but that the SSA denoising performance is superior and can separate the cycle information from the GPS time series more effectively and stably.
This research examines cycle slip detection and repair theory of triple-frequency pseudo-range phase combination and geometry-free combination. Their thresholds are deduced, and the optimum selection method of combinations is investigated. Based on the smallest variance of combinations, and taking ionosphere delay errors during each epoch into consideration, these two combinations fit for BDS triple-frequency data are selected. Finally, BDS data is used in the experiment to validate these two algorithms. The result shows that these two algorithms can detect and repair all the simulated cycle slips in real-time. Taking amount of calculation, complexity and rounding error into account, pseudo-range phase combination is recommended.
n this paper, based on the excluding gross error, we get the space distribution of the continuous GPS sites ’s high frequency in the station coordinate system (NEU coordination system). Then, we use the fractal theory (the measure of relations) to calculate the fractal dimension and its scale-free zone. Finally, we calculate the correlation coefficient and F significant test method in the scale-free zone. The main results are as follows: First, aside from the three consecutive points DXIN, QION and XIAA, where the residual series scale-free region between the correlation coefficients of 099-0.995, the other 24 units have reached a correlation coefficient of 0.995 or more. The 27 consecutive sites’ scale-free zone in the linear regression F-tests rejects the null hypothesis when all scale-free zone in double logarithmic coordinate system can be used least squares linear fit when α=0.005. This is consistent with GPS residual sequence fractal features, thus supporting these conclusions.Second, the percentage of points in the scale-free zone to total points is about 50%-60% at 24 consecutive sites and 40 at the three consecutive sites(BJFS, LUZH and XIAM). This indicates that about half the observations fall under the laws of the fractal nature. Consequently, the noise residual series or sequence (constructed time series and noise models) can play a guiding role. Third, 27 GPS sites fit the fractal characteristics very well in its scale-free zone (the fractal dimension is not the integer), with a fractal dimension range between 1.71 and 1.97. This indicates that GPS part of the residual sequence is contained under the laws of the fractal nature of the observations and should not generally be considered as noise, as supported by our more sophisticated understanding and analysis of GPS observations
Based on multi-frequency combination theory, and using dual-frequency MW and ionospheric residual methods a triple-frequency geometry-free and ionosphere-free combination is built to detect cycle-slips. With real data of BDS triple frequency, it is shown that all cycle-slips can be successfully detected and repaired with these three combination observations.
This paper presents a Beidou only and Beidou/GPS combined pseudorange differential positioning algorithm for the great application demands of Beidou navigation satellite system (BDS) precise navigation at sea. Land fixed-point test and maritime dynamic test for China’s coastal differential stations’ signal are conducted and the test results are analyzed in this paper. Test results show that: 1) when the distance between user and station is less than 300 km, horizontal positioning accuracy of Beidou is better than 1.5 m (95% confidence level), and vertical positioning accuracy is better than 2.5 m (95% confidence level)| 2) positioning accuracy and data efficient rate of GPS+Beidou combined positioning is better than only GPS/Beidou systems| 3) only Beidou positioning accuracy and positioning performance are satisfied with RBN differential system design requirements.
Aimming at the characteristic of three-dimensional laser scanning data，based on the theory of least squares adjustment ，this paper presents a method for point cloud registration，based on point plane geometric feature. Firstly，according to superposition between two planes，model of point cloud registration and error equation are derived， based on geometric feature of point and plane. Secondly，combined error equation of point cloud registration based on feature points，error equation of point cloud registration is derived，based on geometric feature of point and plane. Finally，making a test，using the actual scan data form three-dimensional laser scanner，confirm that this method can improve the accuracy of point cloud registration.
The commonly applied methods of the point-cloud-plane fitting ignored the effects of model error. This paper introduced the penalized least squares to calculate the plane fitting parameters. In the process of calculating, the penalized least squares considers the parameter and the Semi-Parameters at the same time. The fitting precision is greatly improved. We test the results of three different methods (the least squares, eigen-value and penalized least squares methods) on inclined plane, horizontal plane and vertical plane. In comparison, with the rest of methods, the penalized least squares is best.
Large amounts of data will have an adversely impact on point cloud’s processing, storage, transmission and display. In order to improve the point cloud’s data processing efficiency, it is necessary to simply point cloud data and reduce data redundancy. Due to the large quantity and complex surface features of terrain point cloud data, the point cloud simplification algorithm for terrain data is proposed.We use K-D Tree to search the point’s K neighborhood and the moving least squares method to calculate the curvature of each point. Through the vision of curvature, point cloud data is simplified based on distance in the flat area to improve the efficiency of the algorithm and on the basis of curvature in the steep area to retain the feature information. According to the quantitative evaluation method,based on the entropy theory and verified by the example, it is indicated that the proposed new simplification algorithm for terrain data can simply the data in high-fidelity with high-precision. It is highly efficient feasible and universally applicable.
Aiming at the issue of lacking unified fixed weight criterion in plane fitting of point clouds based on weighted total least squares, two methods that prior incident angle weighted and distance weighted are proposed, and three new plane fitting algorithms that robust weighted total least squares based on intensity (RWTLSI), weighted total least squares based on prior incident angle (WTLSPIA-1) and weighted total least squares based on distance (WTLSD) are structured with combining robust estimation. With the various algorithms of weighted total least squares applied to fit plane point clouds data from scanning different reflective material, as examples show, the precision evaluation index of the distance weighted total least square method based on distance weighted method is superior to other algorithms, which win the best fitting effects.
A method of structured total least squares for space straight line fitting is presented. It considers the errors of three-dimensional coordinates and ensures the sum of distance from points to a line is least. The examples show that the method is reliable and effective.
The robust Kalman filtering can resist errors from observation data or inaccurate state model that depend on the reasonability of equivalent weight. Usually the existed equivalent weight functions are defined as a segment function, which involves the selection of critical values for segment weight-decreasing. The selection is generally based on the confidence level of error tests or by experience, and it will never be changed once fixed. In order to further improve the efficiency of robust estimation, a new robust Kalman filtering with a continuous variable equivalent weight function is designed. Comparison and analysis has also been made between the new scheme and the common scheme. It can be concluded that the new designed scheme of robust weight determination has a better robust effect.
Based on uncertainty theory, this paper establishes the parameter-bounded adjustment model and overcomes the defects of inequality-constrained adjustment. Due to the least squares, the problem is converted into a quadratic programming problem with box constraints, proposes a new algorithm to calculate the optimal values of parameters, and gives the statistical properties of parameter estimation. Numerical experiments validate that the new algorithm is simple, feasible, has a faster convergence speed, and show that the algorithm can reduce some numerical uncertainty.
There is a close relationship between gravity and tectonic stress. The tectonic stress field in Sichuan-Yunnan area is computed with the EGM2008 gravity model and ground gravity observation data respectively. Characteristics of the tectonic stress field in the Sichuan-Yunnan area are summarized. The results show that the inversion results are consistent. The tectonic stress field in Sichuan-Yunnan area is complicated. Tectonic stress distribution is gathered in high degree obviously in the Longmenshan and the Jiali fault zones, where average tectonic stress is higher than in other zones. The tectonic stress results observed in the Longmenshan and Jiali fault zones reflect that the tectonic movement is active in the region and corresponds with historical earthquake data.
We estimate the temporal and spatial variation of Antarctic ice sheet elevation using repeat track analysis based on all of the ICESat operational periods (19 campaigns), the results show that the elevation of the ice sheet decreased for the past years. Due to the influence of the GIA, We analysis the contribution of three different GIA model and find the average height rates derived from the ICESat campaigns is about -1.17--1 cm/a based on the three different GIA models.
Based on collation and adjustment of the 1998, 2006 and 2013 leveling survey data of the Shanxi-Hebei-Inner Mongolia region, we obtain the vertical deformation rate and gradient for the periods of 1998-2006 and 2006-2013. We then analyze the regional geological unit of the Shanxi-Hebei-Inner Mongolia vertical deformation rates, the evolution of the gradient and the main fault zone activity properties. The result shows that the vertical deformation rise rate of Lüliang mountain increases, the vertical deformation rise rate of Taihang mountain declines, and the Yunzhong mountain and Xizhou mountain piedmont fault turns to reverse fault. The activity of Kouquan fault, North Yanggao basin fault, South Yanggao basin fault and South Weixian basin fault, all present normal fault activity.
The long term prediction of Earth rotation parameters were performed by using LS+AR combing model, fluid excitation functions including atmospheric angular momentum and ocean angular momentum, respectively. Numerical tests showed that the prediction precision computed from fluid excitation functions was better than those from LS+AR combing model, and the prediction precision from atmospheric angular momentum excitation function was better than those from ocean angular momentum.
Savage’s strike-slip formula was improved in this paper, by retaining the original formula to reflect the characteristics of the strike-slip fault and containing the information on fault dip, which reflects the influence of fault dip to surface displacement. When the fault dip is not vertical, the conclusions are as follows: 1) The center of inter-seismic deformation curve is not at the fault outcropping but at the fault lock and slide boundary which projects to the surface. 2) There is the geometric relationship between fault dip δ and locking depth d：tanδ=d/doffset. 3) The earthquake ruptures along the fault plane, its location is inconsistent with the center of the inter-seismic deformation curve, so the displacement of upper and lower plates is asymmetry when earthquake occurs. Because this process is applicable to dip-slip faults, improved dip-slip fault displacement formula is given in the paper.
The paper presents an algorithm for the combined calculation of the corner reflector interferometric synthetic aperture radar (CRInSAR) and the permanent scatters interferometric synthetic aperture radar (PSInSAR) techniques. The algorithm uses the subsidence rates and elevation corrections calculated on the CR points as initial data for the PS baseline network. It then estimates the total optimum solutions of linear deformation rates and elevation corrections through the parametric adjustment method in the PS network. Experiments with simulated data and real data are carried out to estimate the feasibility of the algorithm. The simulation results show that the accuracy of linear deformation rates is ±0.37 mm/a, while that of elevation correction is ±0.5 m. The PS deformation rates inversed through the real data experiment show good consistency with that of leveling deformation monitoring. It can be inferred that the method presented is feasible in field regional deformation monitoring.
A micro-deformation monitoring method using a fusion of GPS, corner reflector and InSAR, is applied in Shuping landslide deformation monitoring. The mean difference between the deformation monitoring results obtained by the proposed method and measured GPS value is 3.33 mm, and RMS is 3.16 mm. These results show that using this method is feasible for micro-deformation monitoring.
The precision of D-InSAR techniques for monitoring the planar near the maximum subsidence monitoring is low, and we can only get limited monitoring deformation value by high precision leveling. So we use the ensemble Kalman filter method to assimilate D-InSAR and level monitoring results, in order to achieve the goal of high precision planar surface subsidence deformation monitoring. The results show that the collection based on Kalman filtering assimilation results are greatly improved compared with the inversion values and D-InSAR monitoring results, thereby realizing the high precision surface subsidence monitoring. We apply this method to Zouxian-Jining highway in Jining, where the assimilation value total root mean square error is 17.7 mm, which satisfies the requirement of precise deformation monitoring of a high grade highway.
Based on GOCO03S, DTM2006, Airy-Heiskanen models and the spherical harmonic method, taking China and its neighboring area as an example, we here calculate gravity gradient in terms of topographic and isostatic influences. The method used in the paper can eliminate the plan model error. Finally, we provide the isostatic anomaly maps, preliminary analysis, and interpretation.
Some combined GOCE and EGM08 geopotential models are established using Wenzel’s weighted spectral combination approach. Cumulative geoid errors show that combined models have better performance than the EGM08 model alone. Results of geoid differences at GPS/leveling benchmark in America indicate that a Dir4+EGM08 combined model has best performance amongst others, enhancing geoid precision up to 8% relative to EGM08 model.
In recent years, all kinds of global and regional continuous GPS tracking station networks have been established around the world. We apply these networks to enhance the resolution and precision of existing global ocean tide models in coastal areas. In this paper, we obtain one-year PPP-based position time series of four stations (AC67, AC43, AC39, SHAO), and then extract and inverse the corresponding ocean tidal periodic information, specifically eight major tidal constituents of OTL, by using fast Fourier transformation (FFT). It is indicated that PPP-derived OTL agree well with those calculated by the DTU10, EOT11a, GOT4.8, TPXO.7.2 and FES2004 models, and the RMS (root mean squares) of the differences between them is at the millimeter level. It is demonstrated that the estimates of OTL displacement by the PPP technique are available
This article discusses the basic principle of bathymetry inversion in frequency domains., In addition, the response function relationship between the bathymetry and gravity anomaly is analyzed briefly. Based on the uncompensated plate model, the bathymetry in South China Sea is predicted from satellite altimetry-derived gravity anomaly and the ETOPO1 model. The precision of the predicted bathymetry model is about 10% using the ETOPO1 model and ship-derived bathymetry data. The advantage of this technique is that there is no need to use the ship borne bathymetry data as control points, and the disadvantage is that it requires a prior bathymetry model as a reference. Furthermore, in shallow sea and seamount areas, the precision is a bit lower, and the seamount peak is underestimated excessively.
According to general relativity theory, the running rate and orthometric height of precise clock's are closely related, and consequently the height difference can be determined by measuring the running rate difference between two clocks located at two stations. Using the time-frequency difference in observation series by the two-way satellite time and frequency transfer and those by GNSS at four stations released by the Bureau International des Poids et Mesures, we determine the geopotential difference and height difference between arbitrary pairs of the four stations based upon the clock comparison method. Compared to the EGM2008 model results, the standard deviations of the geopotential and height differences are respectively 308.5 m2/s2 and 31.5 m. Experimental results are consistent with the current stability level 10-15 of the atomic clocks equipped in the time-keeping stations.
n this paper, we propose a new method to extract local ionospheric Total Electron Content (TEC) from combined GPS phase observations and global ionospheric maps, considering the effect of differential code bias on phase smoothing code observations, as well as the lower accuracy of global ionospheric maps. This method does not need to consider the impact of differential code bias in the absence of code observations. The results show that the accuracy of single-frequency positioning using ionospheric delay correction with the proposed method improves significantly compared to that of global ionospheric maps. Moreover, overall it is consistent with the correction method of phase smooth code observations under different regions and different activity conditions of ionosphere.
The paper obtains one to four order wavelet details of gravity anomalies through the 1[DK]∶200 000 Bouguer gravity anomaly wavelet multi-scale transformation data of Yubei. Horizontal and vertical anomalies of gravity field in the research area are analyzed and interpreted based on geological tectonic environment. Moreover, 11 main faults in the southeast segment of Taihang mountain and their spatial distribution characteristics are studied using their diverse wavelet transformation information. Furthermore, the approximate depths of these faults are inferred.
〗In this paper we use the repeated gravity measurements of the western Yunnan gravity network with the data length of 1986-2009, as well as absolute gravity observations at Xia Guan, Li Jiang, and Kun Min gravity sites. Linear gravity rate models are employed to estimate the time variation geophysical information. We build dynamic adjustment models under the constraints of absolute gravity observations, and discuss several key questions including the variance metric for both repeated and absolute gravity measurements, the initial values of the models and the iterations’,robust estimation, and statistic hypothesis testing. We obtain the annual gravity rate at each site in the western Yunnan network with a range of (-0.039 5-0.024 1)×10-5ms-2/a, and the precision with a range of (0.001-0.0298) ×10-5ms-2/a, with the difference of (0.003-0.020)×10-5ms-2/a, as compared with the static adjustment method. When we process the national gravity network or the regional gravity network over a relatively large area, especially with multi-network and multi-campaign gravity measurements, the dynamic adjustment model developed in this work can obtain the gravity variation under the united space-time status.
High-rate (1 Hz) GPS data from the 2010 Mw7.2 El Mayor-Cucapah earthquake are used to analyze ground motion characteristics, estimate surface wave magnitude by the empirical equation that Gutenberg deduced in 1945, and research the application scope in earthquake magnitude. The results show that for GPS sites within 50-350 km of the epicenter, using its peak displacement, the surface wave magnitude is 7.21, which is consistent with USGS reported Mw7.2. Using sites of epicentral distance greater than 350 km, the magnitude values are within 7.6 to 8.0, which is much larger than Mw7.2. So we suggest that when establishing an empirical model of inversion surface wave magnitude with high-rate GPS, its application scope should be considered.
Based on the seismic phase record characteristics of Deep Seismic Sounding and the fast marching method which has been developed recently, numerical simulation of joint inversion of active source seismic refraction and reflection for 3 D structure is given. The results show that the refraction phase Pg has higher resolution for fine upper crustal structures, and that the middle-lower crustal structure and complex Moho geometry can be well recovered with wide angle reflection phase PmP, although it has poor resolution for the shallow structures. The joint inversion can effectively recover 3 D velocity structure in any depth, with strong velocity contrasts and the morphological characteristics of Moho interface.
To make the RZB borehole strain meter work normally under kilometer depth, a range extension mechanism was designed. Based on a ceramic motor and the RS485 bus, the mechanism can remotely make up for the deformation caused by water pressure and achieve the goal of the range extension. Some simulation experiments for up to 10 MPa pressure were performed in the laboratory, and the test results showed that: the sensor 1 was over range under the pressure of 5 MPa| after the range extension, the sensor 1 worked well under the pressure of 10 MPa.
Using observation data of different time scales from Gaotai station’s 4-component borehole strain, we calculate the relative calibration coefficient, the self-test accuracy and the correlation coefficient of plane strain. Through the analysis, we derive the following conclusions: for long term scale observation data quality evaluation, conversion of strain and earthquake research, relative calibration processing should choose five daily average or the daily average of continuous observation data| for shorter term scale observation data quality, the relative calibration data processing should choose the duration.
We analyze the earth's free oscillation induced by the M9.0 earthquake off the east coast of Japan, using data observed with the DZW gravimeter at China's 14 observatory stations, and the 2D and 3D time frequency characteristics are displayed for the first time. Comparing the spectrum figures of the 14 observatory stations, we found that the energy of the earth free oscillation is uniformly distributed in the frequency axis, and shows frequency information clearly. However, there are differences in the time axis, the distribution of the energy of the earth free oscillation is similar at most stations, but narrower at the Yichang, Xichangxiaomiao, Xiamen and Shenzhen stations.
Borrowing ideas from data mining techniques, a method of picking up characteristic values from time series is designed to detect earthquake precursor observation data. Significant deviations from normal observation data could be identified rapidly using this method. It makes significant sense to adopt this method for the task of large data preprocessing of earthquake precursor observation data.
The strain abnormity magnitude range is 10-9-10-6 from cave temperature’s annual varying, air pressure rising, heavy rainfall, pumping water and unloading of the pressure-bearing aquifer during 2008 to 2013 at Jiujiang seismic station. The mechanisms of cave strain abnormity primarily are the cave material’s temperature effect and extra-stress load-uploading process of the observation hill body. Cave strain observation is sensitive to local stress-stain field, and it may provide the opportunity to capture the strong earthquakes’ precursory abnormity.
Using the continuous waveform data observed by seismic network of Henan province from 2008 to 2012, we analyzed the ambient seismic noise in Henan province by calculating the power spectrum density(PDS) and probability density function(PDF). Using the PDF, we can provide an important basis for quantitative assessment of the seismic data quality, seismic station optimization and construction.
