Table of Content

25 October 2010, Volume 39 Issue 5

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测绘快报

Establishing the JiLin West Quasi-Geoid Based on CQG2000

2010, 39(5):  441-443. 

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As the precision of CQG2000 cannot meet the need of practical work, a residual model method of combining gravity quasi-geoid and GPS level has been presented. Based on CQG2000 and GPS level points with comparatively high density, the JiLin West Quasi-Geoid (JLWQG) is determined by this residual model method. This paper also discussed the triangulation bilinear interpolation algorithm and its applicability for JLWQG. The study shows that the precision of JLWQG is up to ±0.05m. And JLWQG is widely and efficiently used in the renewal of basic surveying and mapping in the west of JiLin.

学术论文

The Adaptive Fusion of Multi-source Gravity Data in Bohai Gulf

¹, ²

2010, 39(5):  444-449. 

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The least square stepwise collocation formula is derived according to the induction method, so the self covariance and mutual covariance of the observation signals can be described in detail.Based on the stepwise collocation, the adaptive fusion method is established whose main content is adjusting the self covariance and mutually covariance of the observation signals. The airborne gravity data, satellite altimetry gravity dada and land gravity data are fused by using the two fusion mode, which are the fusion based on observation signals and fusion based on the results of stepwise collocation. The computation results show that the accuracy and reliability of the fusion based on observation signals is better than the other mode. According to the shipborne gravity data verifying, the final fusion accuracy is better than 3.7mgal .

Non-singular Expression of the Disturbing Gravity Gradients

², ³,

2010, 39(5):  450-457. 

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If the disturbing gravity gradients are expressed by earth-centered spherical coordinates in the local north-oriented reference frame, the first- and second-order derivatives of the Legendre functions of the colatitude and the sine function of colatitude in the denominator which tend to infinity when the computational point is approaching the poles. Therefore, the non-singular computational formulas of the first- and second-order derivatives of the Legendre functions of the colatitude and the are introduced, and the non-singular computational formula of is also deduced. When taking the non-singular computational formulas of the first- and second-order derivatives of the Legendre functions of the colatitude and the 、 into the computation of each component of the disturbing gravity gradients, the complex situation that the m equals to 0, 1, 2, and any other numerical values are also considered, and the non-singular particular computational models of each component of the disturbing gravity gradients are constructed. The simulation experimentation shows that the particular computational models constructed in this paper not only completely fulfill the precision demand of the computation of the current satellite gravity gradients, and the models are steady, credible and easy to be programmable realized.

Study of Regularization Based on Signal-to-noise Index in Airborne Gravity Downward to the Earth Surface

2010, 39(5):  458-464. 

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This paper studies regularization in airborne gravity downward to the earth surface. First, the relationship between multicollinearity structure in design matrix of ill-posed linear model and its harm to the unknown parameters is analysed. The information if the unknown parameters suffer the harm are extracted by an index called signal-to-noise ratio, which reveals multicollinearity structure to some extent. Second, regularization based on signal-to-noise ratio(SNR) is put forward. The regularization matrix is constructed according to the ratio. The regularization parameter is selected by minimization the mean squared error of roots to the solution. The regularization matrix constructed in this paper need not use additional physics or priori information, so the algorithm provided in this paper gives a new way of regularization when this kind of information is short of. At last conclutions are drawn from numerical experimerts: compared with ordinary regularization(OR), SNR is better in noise filtering and information fidelity.

The Simulation Research on the Tikhonov Regularization Applied in Gravity Field Determination of GOCE Satellite Mission

2010, 39(5):  465-470. 

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GOCE satellite has been launched in 17 March 2009, the main objective of which is to provide a global gravity field model up to the degree and order 200. At the same time, the accuracies of the geoid and the gravity anomaly are 1-2 cm and 1 mGal respectively. Because of the distribution of observation data (Polar Gap) and the downward continuation problem, to the determination of the high-degree gravity field model using GOCE data is usually an ill-posed problem, which can be dealt with by regularization techniques. The Tikhonov regularization is widely applied in the geodesy, the principle of which is discussed in this paper, also including the mathematical models of four types of regularization matrices (zero-order, first-order, second-order and Kaula) and the regularization parameter selection methods: L-curve and GCV. The validation of zero-order, first-order and Kaula regularization matrices applied in the gravity field determination with GOCE simulated data is analyzed based on the SA method. And also the applicability of L-curve and GCV is discussed using the simulated data. The results show that the accuracies of the optimized solutions (selected by minimizing geoid MSE) with the three types of regularization matrices are at the same level. The key point is the selection of the corresponding regularization parameter. The results also show that GCV and L-curve can be applied in the regularization parameter estimation, and the former method is more stable than the latter one.

Least-squares Collocation Harmonic Analysis of the Radial Satellite Gravity Gradients

2010, 39(5):  471-477. 

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The least-squares collocation harmonic analysis method, which is used to determine the earth geopotential coefficients from the radial satellite gravity gradient, is deeply studied. The principle of the least-squares collocation is firstly dissertated, and the covariance and self-covariance matrix between the disturbing gravity gradients and spherical harmonics are derived. When the disturbing gravity gradients are in the regularized equi-longitude grid, the covariance matrix between geopotential and disturbing gravity gradients has the configuration of blocked Toeplitz circulation matrix, and its degree can be lowered by using the fast Fourier transform technology effectively. Truncated singular value decomposition (TSVD) which is used to solve the ill-posed problem of covariance matrix is studied. The complete formula of least-squares collocation harmonic analysis of the radial gravity gradient is finally obtained. The simulation experiment results show that the least-squares collocation harmonic analysis based on TSVD can recover the global gravity field in a rather high precision and validity and practicability of algorithms in this paper are also testified.

Precise Point Positioning (PPP) Algorithm Based on GPS Dual-frequency Raw Observations and Its Application

2010, 39(5):  478-483. 

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A PPP algorithm based on GPS dual-frequency raw observations was presented, instead of forming the ionosphere-free code and phase observables like these traditional PPP models, the effects of ionospheric delays are modeled through including the Line Of Sight (LOS) ionospheric delay parameters into the state vector which is estimated using the Extended Kalman Filter (EKF) technique. This alternative algorithm could avoid the adverse effect of amplified mutipath and measurement errors existing in the combined observations, besides, several constraints can be introduced to the LOS ionospheric delay parameters during the filtering process，to improve the convergence of the filter to more reliable and precise solutions; The LOS ionospheric delays could be obtained simultaneously with other unknown parameters, which facilitate the research on ionosphere much; Besides, the recursive DIA-procedure is adopted as quality control strategy to guarantee the reliability of the estimators from our PPP implementations. The performance of our algorithm was evaluated for different positioning applications: static, low-dynamic and high-dynamic test, a position accuracy of about 1~2 cm and 7~8 cm can be achieved respectively for static and kinematic positioning, which demonstrate the feasibility and effectiveness of this new algorithm.

Precision Orbit Determination of MGS Mapping Phase Arcs and Martian Gravity Field Model Solution

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2010, 39(5):  484-490. 

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POD (Precision orbit determination) of Mars exploration spacecraft is vital to its mission and scientific objects implementation. Besides using for POD, Martian gravity field is an important constraint for researches about Mars internal structure, Mars surface mass transformation and Mars origin and revolutionary. Considering the importance of Mars spacecraft POD and Martian gravity field, POD of MGS (Mars Global Surveyor) is done using nearly two months tracking data during mapping phase, and the accuracy of orbital result is evaluated by orbital overlap analysis. In following Martian gravity field model is solved, and the model accuracy is assessed by methods such as gravity power spectrum, orbital residuals and Mars free-air gravity anomaly, the results show the reasonability of the solution, and dominating Martian gravity field information can be extracted by nearly two months tracking data. The work lays foundation for application of our national Mars exploration mission “YH-1” tracking data in Martian gravity field research..

Influence Analysis of Constraint Conditions on GPS Water Vapor Tomography

2010, 39(5):  491-496. 

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Adding reasonable constraint conditions to the observation equation is one of the main methods to solve the ill-posed problem in the GPS water vapor tomography. Various constraint conditions used in the tomography are presented in detail firstly. Then, its effect on the result of the tomography is analyzed based on two simulated GPS networks with different altitude. As the results shown, with the water vapor changing gently in horizontal direction, the weight matrix of horizontal constraints have a large effect on the result of the tomography. In addition, with small altitude differences between stations in the GPS network it will be difficult to detect the water vapor only using the GPS technique, and the solution of the tomography relies highly on the accuracy of a priori information from other water vapor detectors. However, with large altitude difference between stations, the dependence of the tomography solution on a priori information is decreased obviously, and we thus can get a reliable result even without a priori information.

A Research about Effective Viscosity of Tibetan Plateau Lithosphere Viscoelastic Ductile Layer Use GPS Velocity Fields

,Yamin Dang

2010, 39(5):  497-502. 

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The paper divides crust into two layers: the elastic brittle layer and the viscoelastic ductile layer. Meanwhile, it supposes that the elastic brittle layer approximates to elasticity, and the viscoelastic ductile layer is viscoelastic. The paper calculates strain fields use GPS horizontal velocity, and deduces a strain relation expression between two points. The paper also evaluates interior temperature field of lithosphere by steady heat conductive equation. Under the condition that fracture intensity is equal to creeping intensity, brittle-ductile transition plane is obtained. And calculates varied depth effective viscosity of Tibetan plateau lithosphere. The results show that brittle-ductile transition plane generally locates in middle crust about 22~37km depth. The thicker the crust, the deeper the transition floor. Effective viscosity of middle crustal located in Tibetan plateau is between , and lowe crustal is between . It decreases to at Moho plane.

The Construction and Analysis for Three-tier Point Mass Model of Gravity

Wang Jian-Qaing ¹, ¹, ¹

2010, 39(5):  503-507. 

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The theory of the point-mass model is one of the most important methods for the research of the logical gravity field. In this paper, the approximation theory of point-mass model is briefly introduced, and the characteristics of the elements in the coefficient matrix for the model construction are analyzed by numerical calculation. The observations are calculated by using EGM2008 with degree and order 720 in the region of 32~34N and 103~105E. The four-tier point-mass groups based on the geopotential model with degree and order 36 are from low frequency to high frequency to approximate the gravity field. The results of the tests show that the effect of three-tier point-mass model is better than others and the truncation error of gravity disturbance created by using the point-mass model is less than 2 mGal on the radial direction.

Coons Curved Surface Reconstruction Method of Marine Gravity Anomaly Map for Navigation

2010, 39(5):  508-515. 

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Based on the continuation property of the Earth’s gravity field，the Coons curved surface modeling of computer graphics was introduced into the reconstruction of the marine gravity anomalies map for navigation, and both the bilinear Coons curved surface gravity anomaly model and bi-cubic C1Coons curved surface gravity anomaly model for different boundary curves were established. Through the analysis of data within experimental area, it was showed that the accuracy of gravity anomaly model based on Coons curved surface is better than that based on bilinear interpolation model, and furthermore, the more boundary conditions, the better the model accuracy would be. With the global SRTM30plus oceanic depth data, the reconstruction of gravity anomaly map based on Coons curved surface using Bouger anomaly was made, and the accuracy was improved by 25% compared with the direct modeling using free air gravity anomalies.

A method for the shortest time routing based on an instantaneous depth model

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2010, 39(5):  516-521. 

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An optimal planned route is a foundation of safe and economical navigation. This paper proposes a method for the shortest time routing based on an instantaneous depth model. Firstly, an instantaneous model is constructed based static depths in a chart and a tidal model in a sea area, then obstacles are acquired and the navigability of a route is analyzed. Secondly, the shortest time path is searched using a dynamic programming method. Finally, the path is optimized by the strategies including excluding obstacles outside the rectangle border of all nodes, searching close nodes in next stage and deleting redundant nodes for a more direct navigation. Experimental results demonstrate: (1) the proposed method can analyze the navigability of the routes dynamically and acquire the shortest time route; (2) the route acquired by the proposed method has the shortest time than that by the traditional methods; (3) the shortest route depends on the start time of navigation and the ship speed.

Integrated Localization Algorithm for DGPS/DR Based on SUT-EKF

2010, 39(5):  528-533. 

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Aiming at the integrated localization issue for mobile robot based on DGPS/DR, an algorithm based on scale unscented transformation and extended kalman filter (SUT-EKF) is used. For the characteristic of nonlinear state equation and linear measurement equation, the robot location can be predicted by SUT and can be updated with new observations by EKF. The algorithm doesn’t compute the Jacobian matrix, it can decrease effectively the error of nonlinear system brought by the linearization. Simulation results show that the new algorithm has better filtering precision and stability and provide an effective approach for the integrated localization system based on DGPS/DR.

The Adaption of A* Algorithm for Least-Time Paths in Time-Dependent Transportation Networks with Turn Delays

2010, 39(5):  534-539. 

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The shortest path algorithms used widely by dynamic route planners only consider traffic information at some definite moment so as to ignore the fact that the travel time along a link is dependent on the time to enter it. Besides, those traditional node-labelling shortest path algorithms are no longer effective in view of turn delays at intersections (or nodes). In this paper, a link-based time-dependent network model is built by re-defining the First-In-First-Out (FIFO) condition with turn delay time introduced into, and then a link-labelling time-dependent A* shortest path algorithm is developed by expanding the evaluation function to time dimension and applying Euclidian distance divided by maximum possible driving speed as the heuristic evaluator. An experiment on the real road network shows that the proposed algorithm is capable of forecasting and bypassing those forthcoming traffic congestions and then shortening travel time, only with a cost of about 10 percent more computational time than the traditional algorithms. Moreover, it is able to improve overall efficiency of route planning heavily because of its no longer need to the frequent path re-optimization processes.

A Classification-oriented Method of Feature Image Generation for Vehicle-borne Laser Scanning Point Clouds

2010, 39(5):  540-545. 

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Vehicle-borne laser scanning is a popular and rapid means to capture dense point clouds in urban areas. Automated classification of point clouds is a precondition for further object extraction, segmentation, 3D reconstruction. This paper proposes an efficient method of feature image generation of point clouds to automatically classify dense point clouds into different categories, such as terrain points, building points. The proposed method first uses planar projection to sort points into different grids, then calculates the weights and feature values of grids according to the distribution of laser scanning points, and finally generates the feature image of point clouds. Thus, the proposed method adopts contour extraction and tracing means to extract the boundaries and point clouds of man-made objects (e.g., buildings and trees) in 3D based on the image generated. Experiments show that the proposed method provides a promising solution for classifying and extracting man-made objects from vehicle-borne laser scanning point clouds.

A Driver Route Prediction Based Map-matching Algorithm Integrating Uncertain Reasoning

2010, 39(5):  546-550. 

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Map-Matching is one of the important parts of the vehicular navigation system. This paper provided a brief introduction of various map matching algorithm firstly, a novel integrated algorithm combining route prediction with uncertain reasoning was proposed based on previous researching. In the proposed algorithm, the cloud model, a powerful tool to perform uncertain converting between numerical quantitative analysis to conceptual qualitative analysis, was firstly used to calculate the credibility of positioning point to candidate roads by uncertain reference with current locating data. Then, a Hidden Markov Model (HMM) was built to predict the driver’s routes and destinations. Through redesigning observation function in HMM, an integrated map matching algorithm was established by combining route predicting information with current matching approach. Additionally, the learning algorithm was carried out to support the algorithm and update the information. Finally, the experimental results demonstrate the effectiveness of the proposed algorithm: it can predict a driver’s routs to improve the accuracy and real-time characteristic of map matching algorithm according to the utility of pre-matching.