2005 Vol. 30, No. 10
In this paper, the meaning for China to project radio satellite is discussed. According the nature of VLBI technique and technology needed to realize the SVLBI missions, a set of unique operational requirements are proposed. The key technologies and methods for radio satellite and its correlated establishments are analyzed and summarized.
This paper discusses the polygon medial axis definition of GIS and calculation geometry,and their main distinguishing feature, pointes out that the polygon medial axis should be the locu of the equal-distance points to two or more edges of the polygon;analyzes the relevant different algorithm and cases in practice, and proposes the geometry means in theory relatively rigid and widely meeting the requirements in practice-dotted pair rank method and the map algebra polygon medial axis method, utilizes them to offer several polygon medial axis calculation examples.
The dynamic electronic map has the functions of post-displaying the past changes, real-time tracing the changes being happened, predicting the changes to be happened and virtual simulating the changes not actually existing. The design of this kind of electronic map has to consider the properties to determine the background layer in a dynamic way, to utilize the temporal scale and temporal generalization, to extend symbol parameters into time related domain, to visualize the change information by multi-scale representation, and to consider the interactive action to control change phenomena. Based on the development experiences, this paper presents the design principles and methods about the aspects above in detail. An example is investigated to design an inland chart to moniter the position and working status of buoys.
Based on the analysis of the polymorphism of constrained edges, this paper presentes that virtual points be used to describe the intersection of constrained edges, developes a new algorithm, called as influence domain retriangulating for virtual point (IDRVP), to delete constrained edges with virtual points. The algorithm is completed in topology, and the algorithm is tested by some applications cases.
Based on the analysis of the store methods of Kiwi format's map display data, the dynamic organization methods of these data in the navigation software memory are studied. This paper improves the two-level buffer method of map display and a dual buffer pond strategy of the map display, in which data buffer pool and map bitmap buffer pool are used to manage data pre-load and map pre-draw in the process of drawing map. The results demonstrate the dynamic organization methods and the dual buffer pool map display strategy can improve the speed of map display.
In order to acquire a fine map of the moon surface, this paper proposes a Laser orbit determination for the Chang-E satellite orbiting the moon. Three SLR stations survey simultaneously the distances from three ground stations known their coordinates to the Chang-E satellite. The algorithm using SLR results is discussed to solve for real-time positions of the Chang-E satellite orbiting the moon. This paper discusses also to solve for the orbit parameters of the Chang-E satellite orbiting the moon by means of the results from SLR single station observation.
A directionally dependent adaptive SIGMA median filter is developed for the noise removal in SAR interferometry (InSAR) derived digital elevation model (DEM). In this filter, the directionally dependent window is selected as the filter window. The performance of median filter, elevation dependent adaptive SIGMA median filter, and directionally dependent adaptive SIGMA median filter are tested on both InSAR Tandem DEM and simulated high-level noisy DEM. From the comparison, the directionally dependent adaptive SIGMA median filter is the most effective one not only in the noise removing but also in the boundary preserve.
The multipath has long been considered a major error source in GPS applications. This paper analyzes the characteristics of the GPS signal multipath effects, bases on which do an experiment that considers the characteristics of dynamic deformation monitoring. The solution results of observation data to successive two days are processed by a method, which combines the wavelet filtering and the differential correction between successive two days. The research demonstrates that the multipath errors have stronger repeatability on successive days; after significantly mitigating the influence of multipath effects, the accuracy of three-dimensional positioning for GPS dynamic deformation monitoring can attain the mm level, an obvious accuracy improving particularly in vertical component. The characteristics of GPS signal multipath, the experimental scheme and the qualitative and quantitative analysis of results are detailed.
In order to avoid estimating the noise statistics in navigation, self-tuning Kalman filtering is introduced. When the system contains outliers in navigation, the estimated state vector by self-tuning Kalman filtering is influenced. To get a reliable result, an equivalent weight based on robust M-estimator is applied in the process of self-tuning Kalman filtering; robust self-tuning Kalman filtering is then proposed in this paper. A real kinematic system is tested. It is shown by real calculation that the robust self-tuning Kalman filtering is not only adaptively estimate the state vector, but also guarantee the reliability of the kinematic state estimates.
The algorithm of rapid ambiguity resolution on-the-fly for single frequency receivers is presented in this paper, Firstly, a method of QR decomposition is applied to decompose the observation matrix of satellites, so as to decrease dimensions of the matrix and to satisfy rapid ambiguity resolution by matrix transformation that can separate out the ambiguity parameter from the position parameter, the LAMBDA method is used to search the fixed ambiguity. The algorithm is applied to two different types of real data to show its effectiveness. Experimental results show that the proposed method is fast and efficient for kinematical users to make use of single frequency receivers to perform DGPS positioning. The method may be used in areas requiring accurate positioning such as navigation and geodesy.
This paper discusses the ellipsoid transformation problem in the establishment of local independence coordinate reference system using GPS technique. Based on a general ellipsoid selection model, describes the ellipsoid expanding model, the ellipsoid shift model and the ellipsoid distortion model respectively and systematically. The similar and different points of these models are analyzed in the view of theoretical approach according the generalized geodesy differential coefficient formula. A new numerical analysis factor is given to describe the impact of before and after the transformation between different ellipsoids.
Taking on Wishart distribution function as likelihood function, this paper represents a maximum likelihood estimation of variance components of every coverage aimed at common points in the overlapped coverage. The method can estimate the unknown parameters and variance components independent of remnant errors and iterative computation.
The estimated value of parameters' is optimized and unbias only if the error of ad-justment model is not outstanding. Some theory problems affecting parameters estimation are discussed in this paper. Influence and transformation between errors of stochastic and functional models is pointed out as well. For choosing the best adjustment model, a theory formula, which is different from the methods in existing literatures, used to estimate and identify model error is proposed by the author. Based on that theory formula, an applied one and a method of selecting the best model of adjustment system are given.
In this paper, the stochastic properties of gravity field is discussed and formulated. Stochastic properties of the gravity field are revealed dominantly following the appearance of various kinds of high accuracy gravimetric measurements. The higher the accuracy of the measurements the more the incompatibility among them. These combining with the measuring errors indicate that the gravity field should be viewed as a stochastic process, therefore the stochastic boundary value problem is proposed and formulated for the traditional topic. With the aid of the theory of stochastic differential equation, the stochastic integral solution of the stochastic Poisson equation Dirichlet boundary value problem is given, and the relation of stochastic solution with traditional solution of general Poisson equation Dirichlet boundary value problem is also discussed in detail. The results show that if the uncertain factors or random ingredients are leaving out, the stochastic GBVP becomes the traditional classical GBVP.
This paper gives four modes' Clenshaw summation formula of Lengendre function. Based on this, the Clenshaw summation formula with two order are derived respectively to calculate the gravity field parameters from the geopotential coefficient expression model. And the precisions in applying the EGM96 and WDM94 to the gravity field of some experimental survey area are both presented which provides some useful reference in the selection of preliminary geopotential model to construct high resolution gravity field of this local area.
The main activities of joint Amery ice shelf expedition between China and Australia are introduced. Five days continuous GPS observation data collected on one site of Amery ice shelf was post-processed with precise point position (PPP) technology based on precise ephemeris of IGS. Dynamic characteristic of the surface ice of Amery can be derived from PPP solution. Preliminary derived velocity of the site and the motion direction is given in the paper. Semidiurnal oceanic tide and diurnal oceanic tide signal of that site can be achieved from the height variation series of PPP solution. The above solution can be used to the consequent mass balance calculation.
ETM~+ thermal infrared image is used to detect cloud, snow and ice automatically around the Zhongshan Station in Antarctica. Better classification result is achieved by adding thermal radiation where brightness temperature information of ETM~+ is used and texture feature of Entropy derived from gray level co-occurrence matrix. Then we improved the method of the minimum distance classification-the weighted minimum distance classification. This algorithm improves the accuracy to 96.0% in the experimental satellite image of ETM~+ around Zhonshan Station of China in Antarctica.
Data related to geology, landform, property of rock and soil, and land use / cover types are selected to study the stability of reservoir slope based on RS/GIS and numerical simulation in this paper. The reservoir area is visualized for qualitative analysis. The dangerous zones are identified with a combined analysis of statistical evaluation, rule-based classification and numerical simulation of slope stability. The result shows that a combination of RS/GIS and numerical simulation is effective on the evaluation of the stability of rock slopes under complex conditions in the reservoir area.
This paper proposes the pre-selection sample method of Genetic Algorithm fuzzy C mean. The result is that hold the samples nearing the supper plane, delete the samples far off the supper plane, decrease the training set and the storage. Experiences are based on Residence, and according to reducing samples of original. The decision of reducing number of samples according to SVM's numbers of iterative and SV. The variety of iterative and SV numbers should be little while both segmentation results of reducing and original samples are almost same. This method could be extended to other kind of objects.
In this paper, a new method-detector histogram matching is put forward and carried out, first statistics on CBERS-01 0 level data based on each detector is performed , then histogram look up table (LUT) is established using histogram matching method, and LUT is used to make relative radiometric correction of CBERS-01 data. The new method solves the non-linear response problem better, and the quality of image processing is improved obviously, which establish the foundation of the wider application for the CBERS-01 CCD data.
BP Neural network classifier based on Levenberg-Marquardt (L-M) algorithm and its application to remote sensing image classification is discussed in this paper. L-M algorithm is a combination of gradient method and Gauss-Newton method. With the aid of the approximate second derivative, the L-M algorithm is more efficient than the gradient method. Concerned with the training process and accuracy, the L-M algorithm is superior to vary-learning\|rate BP method.
This paper provides a set of intelligent simulation techniques of structure state, which mainly combines intelligent technique of information processing, mix programming, scientific visualization technique, and computer dynamic simulation and emulative technique, visualization interface based on XML technique, soft component technique and engineering database, etc, this method fully integrates advanced computer science and technology with structure analysis and optimization. Then, intelligent visualization is proposed and researched. Especially, two improved gray models (GRBF static prediction model and metabolic GM(1,1) dynamic prediction model ) that can well visualize small sample data simulation are proposed. Finally, fundamental intelligent simulation frame of structure state is built.
This paper puts forward to acquire solid standards of color offset printing by the method of combining color measurement and density and a new term "chromaticity difference circle". Using it the allowance range for solid density standards of color offset printing can be determined.