Table of Content

25 October 2012, Volume 41 Issue 5

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Study Notes on Geographic National Condition Monitoring

2012, 41(5):  633-635. 

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Geographic national condition is the spatial and viewable national conditions. Geographic national condition is to study, analyze and describe national conditions in the view of geography, is to reflect natural, economic and humanistic situations of a state. Geographic national conditions monitoring is necessary for scientifically managing the macro-adjust-regulate of national economy. Surveying, Mapping and Geoinformation Department is a department for obtaining, processing, managing and providing the information of geographic national condition. The Department should organize and construct scientific monitoring system of geographic national condition. Besides, integrating needs of national big project, important stratagem, paroxysmal event and macroscopical administration, the Department should also provide objective and continuous geographic national conditions information.

庆祝宁津生院士80华诞学术论文

GNSS Ambiguity Resolution Using the Lattice Theory

2012, 41(5):  636-645. 

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Fast and reliable ambiguity resolution plays a critical role in GNSS real-time precise positioning, however, the computational complexity of finding the optimal integer ambiguity vector directly will be high, because there is strong correction between ambiguities. Thus the lattice theory was introduced in this paper to reduce the correlation for improving the computational efficiency of ambiguity resolution, and the main decorrelation methods currently existed were also analyzed and transformed into the methods of lattice reduction. Then the Bootstrapping success rate was suggested and tested by an experiment to show the performance of these decorrelation methods used for long-baseline ambiguity resolution with multi-frequency GNSS signals.

Some notes on uncertainty, uncertainty measure and accuracy in satellite navigation

Yuanxi Yang

2012, 41(5):  646-650. 

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Uncertainty always exists in satellite navigation process and results, which includes random errors, systematic errors, outliers and colored noises etc. There are many different measures for evaluating the quality of the navigation results, such as precision, accuracy, reliability and uncertainty, and so on. In practice, the accuracy, precision and error itself are often confused by the users, so are the uncertainty and the uncertainty measures. Especially, the accuracy is often followed several times standard deviation or error percentage. For example, the user range accuracy (URA) index is often followed standard deviation. In this paper, the user range error (URE) is redefined based on the uncertainty concept. Then the URE and URA are distinguished and their relationship is obtained. The uncertainty is distinguished from the uncertainty measure. The often used reliability concept in geodetic adjustment is introduced and described. At last, several notes on the concept of error, precision, accuracy, URE and URA are given.

The Recent Chinese Terrestrial Digital Height Datum Model: Gravimetric Quasi-Geoid CNGG2011

2012, 41(5):  651-660. 

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A Seismic Hazard Evaluating System for Active Faults based on GNSS/InSAR/GIS

2012, 41(5):  661-669. 

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We outlined the method to evaluate seismic hazards of active faults according to the coulomb failure criteria using the GNSS, InSAR, gravity, leveling and other kinds of geodetic observations. The design for the corresponding evaluating system was presented. The system use these geodetic data to determine the crustal deformation near active faults and implement the inversion for the strain, stress and motion parameters of active faults. Then fix the threshold values of stress of active faults from geological and seismic data and analyze the sites, maximum magnitudes, recurrence time and probability of potential earthquakes using the evaluating models. The system exhibits, interprets, and manages the evaluating results using GIS. As a demonstration, we discussed the coseismic coulomb stress triggered by 2008 Wenchuan earthquake, the lasting time of stress disturbing and the earthquake rate of Longmenshan area after shock.

On Stokes’ approach for determining global geoid

2012, 41(5):  670-675. 

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Stokes’ approach is one of the most frequently used approaches for determining the global geoid. However, besides the well-known drawbacks, in Stokes’ approach there still exist theoretical difficulties that are not recognized: in case that the geoid is below the surface of a reference ellipsoid (e.g. the WGS84 ellipsoid), the disturbing potential function is not defined and neither harmonic in the whole region outside the geoid. To take away these difficulties from Stokes’ approach, we choose an inner ellipsoid enclosed by the geoid, with four fundamental parameters, with its center coinciding with that of the WGS84 ellipsoid, and two of which, the geocentric constant and rotation rate, coincide with the corresponding parameters of the WGS84 ellipsoid, and the other two parameters, semi-major axis and flattening, are chosen in such a way that the new normal gravity potential generated by the inner ellipsoid has the constant (the geopotential constant on the geoid) on the surface of the WGS84 ellipsoid. By this new formulation, the disturbing potential function is harmonic in the whole region outside the geoid, and the difficulties existing in the conventional Stokes’ approach vanish.

Water Storage Variations in Heihe River Basin Recovered from GRACE Temporal Gravity Field

2012, 41(5):  676-681. 

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The water storage variation in Heihe River basin is very important to the ecological environment and economic construction. Based on a hybrid filtering scheme of the decorrelated filter P3M6 and 300km Gaussian filter, the terrestrial water storage variations in Heihe River basin are recovered from the GRACE (Gravity Recovery and Climate Experiment) temporal gravity field models GRGS-EIGEN-GL04 for the period from April 2004 until June 2011. By removing the soil moisture and snow mass changes derived from the global hydrological model GLDAS (Global Land Data Assimilation System), the groundwater storage variations in space-time domain are obtained in Heihe river basin, and preliminarily confirmed by the groundwater observations from 23 monitoring wells in Zhangye city. Two conclusions can be drawn from the results: (1) the terrestrial water storage variations tend to reduce with the average rate of 2.3cm/a in terms of equivalent water height (EWH), consistent with the regional climate changes and the results from the global hydrological mode CPC (Climate Prediction Center). (2) The groundwater storage variations show the same tendency at the average loss rate of 2.5cm/a EWH. While the regional groundwater storage rates are different, the average loss rates in upstream and midstream areas are almost the same, but obviously larger than that of downstream area of Heihe River Basin.

Analysis of Long-Term Deformation of Reservoir Using Continuous GPS Observations

2012, 41(5):  682-689. 

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This paper calculated coordinate time series using approximate 23-month continuous GPS short-baseline observations, analyzed the effect of multipath on linear trend and annual signals in time series, and determined the long-term trend of Xilongchi Upper Reservoir. Results verifies the overall stability of Xilongchi Upper Reservoir (located in shanxi province) after first impoundment. However, minor linear deformation was detected on main and auxiliary dam, where station L022 on main dam moves at 2.2 mm/yr in the NE 80° direction, station S071 on northern profile of main dam moves at 2.5 mm/yr in NE109°, station L132 on auxiliary dam moves at 0.7 mm/yr in NW87°, horizontal velocities of station S171 and S191 are less than 0.3 mm/yr. And all stations subside at different degree, where station L022 and L132 subside at 3.8 mm/yr and 1.4 mm/yr, respectively, and rest stations subside less than 1 mm/yr. All stations behave annual movement in both north and east component with amplitude of 0.5 ~ 1 mm. The annual movement of staion L022 and TN01 was possibly cause by the thermal expansion of bedrock, and these of rest stations are both effected by bedrock and surface thermal expansion.

Precision analysis of COMPASS(BeiDou) measurement signals

2012, 41(5):  690-695. 

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A Code-minus-phase Combination (CC) and Multipath (MP) GPS and BeiDou (BD) measurements analysis approach is demonstrated, and the qualitative results of single frequency GPS and BD measurement signals are presented; the performances of CC ambiguity resolution with single frequency data is discussed lastly. The results show that: measurement signals of Geostationary Earth Orbit (GEO) satellite show a higher precision than Inclined Geosynchronous Satellite Orbit (IGSO) satellite; the multipath effects of two kinds of measurement signals behave in long-term and short-term trend. When a long period is utilized, such as 600s, the success rate of CC ambiguity resolution can reach over 90% in GPS L1/L2 and BD B1/B2 frequency, however, when short period is utilized, such as 120s, owing to the stronger multipath effects, the success rate of BD IGSO satellite is the lowest, no more than 50%.

The Study of Global Sea Level Change by Combining Argo Floats Data、Satellite Altimetry and GRACE Observations

2012, 41(5):  696-702. 

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The satellite altimetry、GRACE and Argo floats have provided plenty observations of sea level change, from the steric sea level change derived by Argo floats, we may understand better the sea level change from satellite altimetry and GRACE. The oceanic temperature and salt observed by Argo floats from January 2004 to December 2010 are used to derive the steric sea level anomaly between 65°S~65°N by vertical integration up to a depth of 1000m, the linear trend of global steric sea level is estimated as 0.63 mm/a by using least squares estimation with an annual signal. Within the same time period, the global sea level change estimated from satellite altimetry is about 2.52 mm/a, meanwhile, the sea level change due to oceanic mass change is estimated as 1.84 mm/a from GRACE monthly earthy earthe due to oceanic mass change sea level change from satellite altimetry、GRACE、and Argo floats, one can see that the steric sea level change from Argo floats is close to that derived by combining satellite altimetry and GRACE. The spatial distribution of the steric sea level is also compared and similar patterns can be found.

A Crossover Approach to Calculate the Time-Variable of the Earth Gravity Field Low Degree Zonal Harmonic Terms Based on LEO Cluster

2012, 41(5):  703-708. 

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A crossover point approach was studied for low-cost LEO cluster precise orbit data to recover the global time-variable information without accelerometer system (ACC) or k-band ranging system (KBR) measurements. This approach can reduce the non-gravitational force effects on LEO, obviously. In this paper, we analyzed data coverage and the orbit radial error effect on this approach based on COSMIC (Constellation Observing System for Meteorology Ionosphere & Climate) satellites data. And then, the the low degree zonal harmonic terms, C20 and C30, simulation results of the approach were given.

Discussion of some Issues in the Coastal Precise Quasi-geoid Determination

2012, 41(5):  709-714. 

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For the coastal zone, the multi-source gravity data co-exist and terrain features are diversity, through theoretical analysis and a spreadsheet, some issues in quasi-geoid determination with cm-level precision were discussed, and draw some useful conclusions. Taking into account Molodensky first-order contribution to the height anomaly about 10 ~ 30cm in China's coastal region, refined gravity quasi-geoid should be in the Molodensky frame. Fine topographic effect processing is a fundamental way to handle multi-source gravity data. The algorithm for topography effect, mass compensation and helmert condensation for any height, any type gravity field parameters in earth outer space can be unified. The effect of the inconsistent geodetic reference to the gravity data processing vary with the data processing algorithm. in multi-source gravity data processing procedure such influence can be unpredictable. The terrain Helmert condensation can be introduced to Molodensky framework with any type of gravity data

ROBUST TOTAL LEAST-SQUARES BY ITERATIVE PROCESS OF WEIGHT FUNCTIONS

2012, 41(5):  715-722. 

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The robust Least Squares (LS) adjustment has been extensively studied and successfully applied in the real applications to resist the influence of gross errors in observation. However in the LS adjustment, the coefficient matrix is considered as non-error. Unfortunately variables in coefficient matrix are inevitably error-contaminated when they come from the real observations. Considering the random errors and gross errors may exist both in the observation vector and the coefficient matrix, the robust Total Least Squares (TLS) solution is studied in this paper. The reweighting iteration method is used to detect and identify the gross errors. At the end of the paper, the simulated experiments of three-dimensional similarity coordinate transformation are investigated to prove that using the robust TLS method, the influence of the gross errors can be resisted, and the reliable solution can be obtained.

Study on correlation of temperature changes with GPS station’s non-linear movement

2012, 41(5):  723-728. 

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Spectral Combination Method for Recovering the Earth’s Gravity Field from High-low SST and SGG Data

2012, 41(5):  735-742. 

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High-low satellite-to-satellite tracking (SST-hl) and satellite gravity gradiometry (SGG) employed in GOCE mission are complementary in determining the Earth’s gravity field, but how to effectively use these two types of data is a key problem for the determination of optimal GOCE gravity filed solution. The least-squares spectral combination method for recovering the Earth’s gravity field from the combination of SST-hl and SGG data is studied. The spectral combination computing models and their error estimation formulae for combining disturbing potential T and radial gravity gradient Tzz data, and for combining disturbing potential T and gravity gradient combined components {Tzz-Txx-Tyy} data are established based on spherical harmonic analysis, respectively. Numerical simulation results indicate that the optimal combined solution can be obtained from the spectral combination computing model, which can effectively take into account the accuracy and spectral characteristics with each type of data. Finally, the feasibility and effectiveness of the spectral combination method is validated from GOCE real data processing. Two Earth’s gravity field models named WHU_GOCE_SC01S and WHU_GOCE_SC02S up to degree 180 are recovered from 61 days of GOCE data, the former is solved from T and Tzz, and the latter is solved from T and {Tzz-Txx-Tyy}. The results show that WHU_GOCE_SC02S model is more accurate than WHU_GOCE_SC01S model, and both of the models are more accurate than GOCE time-wise solution, and their total accuracy are most close to GOCE space-wise solution.

Fusion positioning of COMPASS/GPS based on Spatio temporal system unification

2012, 41(5):  743-748. 

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Currently, nine COMPASS satellites have been launched. Regional positioning system of COMPASS has been constructed. It can supply Chinese users with primary three-dimensional positioning. Mainly work of COMPASS is focused on tests and evaluations. This paper discusses conversion of time and coordinates between COMPASS and GPS, broadcasting ephemeris and calculation of satellite coordinates, and precise positioning with COMPASS and GPS. The united precise positioning with COMPASS and GPS is realized, and proved by test results of observations on Sept. 29, 2011. Our tests and results can supply reference to construction of COMPASS II system. Key words: Global Positioning System; Compass Satellite Navigation System; Fusion Positioning

A Hybrid Indicator for Determining the Best Decomposition Scale of Wavelet De-noising

2012, 41(5):  749-755. 

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In this paper, a hybrid indicator is proposed to determine the best grading scale of wavelet de-noising. The variation rule of the root mean square error, signal to noise ratio and smoothness with regard to the decomposition scale is employed to develop the hybrid indicator. Different characteristics in the process of wavelet de-noising are considered to define the hybrid indicator, and the best decomposition scale can be determined by identifying the inflection point of the hybrid indicator. A series of experiments on different signals are utilized to test the effectiveness of the hybrid indictor. The comparisons with current methods are further used to demonstrate the advantages of the hybrid indictor.

学术论文

The Reconstruction of Local Gravity Anomaly Field Based on Gauss Spline Function

2012, 41(5):  756-762. 

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The normal gravity aided navigation theories are based on grid discrete field in most cases. It is indispensable to build the local continuous gravity anomaly field model with high precision and good analytic property before the study on gravity matching algorithm based on continuous field. Fibonacci series searching is applied to optimize the 1-D Gauss spline function interpolation and the algorithm to approximate the local grid gravity anomaly field with the 2-D Gauss spline function based on Fibonacci series search is put forward. To improve the searching speed, the 2-D criterion function was decoupled to two mutually independent 1-D criterion functions at the X and Y direction. Then, the optimal parameters were obtained from the Fibonacci number series searching of these two 1-D criterion functions. Finally, a local continuous gravity anomaly field analytic model which can approximate to local grid data with high precision is attained. Five different parameters were set in the simulation to approximate the gravity anomaly with the variation range -51.185mGal~86.1819mGal. The simulation results shows that approximation mean absolute error of the simulation with optimal parameters is 0.00069 and the mean relative error is to the level of 10-6 which is far less than the simulations with the other parameters. The effectiveness of the reconstruction algorithm was proved by the simulation results and the approximating precision can satisfy the need of matching navigation.

The Application of Compass Triple-frequency Geometry-Free Combination in Cycle-Slip Detection and Correction

2012, 41(5):  763-768. 

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The theory model of Compass triple-frequency geometry-free combination used for cycle-slip detection is deduced, and the detection accuracy is analyzed. Based on the theory of multi-frequency combination, some optimal geometry-free combinations for detecting cycle-slip have been constructed, the insensitive cycle-slip groups of the detection observables have been analyzed. In order to detect all the cycle-slips, two proper geometry-free combinations are simultaneously used to be as the detection observable combination, the better detection observable combinations have been selected. Because the cycle-slips on the three frequencies observations cannot be determined by two linear independence geometry-free combinations, the method of cycle-slip correction by geometry-free detection observable combination and one combination of pseudo range and carrier phase observations has been explored. Using the real Compass triple-frequency data, finally several experiments have been made to test the effect of using (-1,-1,2) ,(-1,2,-1) geometry-free combinations and the (1,3,-4) combination of pseudo range and carrier phase observations. Experiment results show that this method is effective，practical and can be used to the kinematic navigation positioning which can detect all the cycle-slips, no matter the small one or the big, and can correct the cycle-slip based on single epoch.

Road Selection Based on Stroke Functionality in the Network

2012, 41(5):  769-776. 

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A road selection process based on stroke functionality in the network is proposed, in which stroke functionality takes into account its degree of centrality, degree of connectivity and length, and is derived by means of network analysis. The selection set is guaranteed to be connected through adding minimum number of extra most significant strokes. Various structures of urban local and global road networks are used for experiments of selection using the process. The results show that the proposed process performs well upon all the experiment networks of different structures, maintaining the global structure of the network, maintaining typical local structures, and keeping the resulting network well connected. Comparison suggests the proposed process performs better than the conventional stroke length-based selection.

A Hierarchical Approach to Measuring the Information Content of the Contours in a Map

2012, 41(5):  777-783. 

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Quantitative measurement for map information is one of the basic research issues in the field of theoretic cartography. It is recognized as an indicator for evaluating the efficiency of both map design and map generalization as well as the practical value of a map. Taking a typical map, contour map as example, this paper develops a methodology for measuring the information content of the contours in a map in a hierarchy. Existing methods of measuring the information content of a map are first summarized, which are almost based on Shannon information theory. Then, the sources of contour map information and its nature is discovered. It is found that the information of a contour map is able to be described into three levels, namely, element level, neighborhood level and global level. At the element level, it means the information of a contour line; at the neighborhood level, it refers to the information of basic geomorphic unit; and at the global level, the distribution information of whole geomorphology in a contour map is indicated. Moreover, all levels of information are measured from the nature of information source, i.e. variability and diversity. Finally, some practical examples are provided to illustrate the proposed methods in this paper.

Research and Practice of Constitution Variables and Generation Modes of Electronic Map Symbols

2012, 41(5):  784-790. 

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In the process of symbolization of electronic map, visual variable is the key. Through the analysis of shortages of visual variables and symbol constitution elements in the process of symbolization in the situation of electronic map, concept of constitution variables is brought forward. Then, profound meanings and representation forms of constitution variables are studied, and multifold symbol generation modes are discussed based on constitution variables. At last, electronic map symbol fast generation module is made to validate the theories, which proves that it is easier to draw symbols with computer and the symbols are preciser and prettier. On one hand, study of constitution variables and generation modes can make us understand visual variables deeply and boost the development of electronic map theories. On the other hand, it will also provide new method to the development of electronic mapping technologies and promote the evolution of automatization symbolization, individuation mapping, automatization mapping and intellectualized mapping.