2005 Vol. 30, No. 6
The principle of the fictitious compress recovery is summarized and its general applications to geoscience especially in the boundary value problems are discussed.As new application examples,Runge theorem,Runge-Krarup theorem,and Keldysh-Lavrentiev theorem are naturally and simply derived based on the principle of the fictitious compress recovery.
The effects of SSC(small-scale sub-lithospheric convection) on seafloor topography are investigated by formulating a 2D thermal convection model that is parallel to plate motion. Instead of closed boundary conditions which will bring large pressure effects because of return flow, a flow through boundary condition is adopted. The results show that the SSC can cause the topography flattening only in constant viscosity model; for the model with temperature-dependent viscosity, although the SSC enhances the surface heat flux, it has little effects on topography.
Based on AR model and its extension to CAR model, this paper presents a new method for centralized modelling for time series. Dynamic model and static model are compared. The result shows that the dynamic model of time series analysis is an important system analysis and an advanced forecast one among statistics forecast method. Its forecast precision is high. Static model is suitable for interposition.
ARCE (ambiguity resolution using constraint equation) is a new method for resolving the integer ambiguities based on LSE (least-squares estimate) and null space. In this paper, ARCE is improved for the case that the observation time span is short and there are only a few epoch observations. The normal matrix is badly ill-conditioned in GPS rapid positioning if the observation epochs are fewer, which causes the result of LSE unreliable. In this instance, it is difficult to fix the integer ambiguities correctly using ARCE. On the basis of TIKHONOV regularization theorem, a new regularizer is designed to mitigate the ill-condition of the normal matrix. The accurate float ambiguity solutions are obtained and the search range of the integer ambiguities decreases greatly. Then, the integer ambiguities are fixed for reference of ARCE theorem and the success rate of fixing the integer ambiguities is high.
In applying typical Kalman filtering technique to the optimal estimation of motion state of LEOs, there are some limitations, such as divergence of filter because of inaccurate of dynamic noise and observation noise, distortion of estimation of Kalman filter caused by measurement pollution and being not positive definite of covariance matrix due to computing rounding errors. In order to cope with these limitations, a comprehensive Kalman filter is presented in this paper. This filter is a combination of adaptive UD decomposition Kalman filter with QUAD method. It applies the QUAD method to detect and correct the gross errors in observations, uses UD decomposition technique to improve computation precision and overcome the instability of filter caused by instability of values.
Combining the genetic algorithm with the ambiguity function method, this paper presents a new approach to perform GPS carrier-phase ambiguity resolution using sing-epoch C/A code and single-epoch L_1 carrier phase observation data.
The effect of Earth’s oblateness in the inversion of GPS occultation data and corresponding correcting method are studied. By using observed CHAMP orbit ephemeredes and MSISE-90 dry air model and regarding Earth as a sphere and an ellipsoid respectively, excess phase delays are simulated and the simulated data are retrieved under different schemes. The comparisons between the Inverted temperature profiles and the model temperature profiles show that when inverting observed data, we will get temperature results with large errors if the effect of Earth’s oblateness is omitted. The correction method is tested useful because the temperature errors decreased obviously with this method.
With GPS, VLBI, SLR and other techniques Crustal Movement Observation Network of China (CMONOC) provides a large scale network of crustal observation of high accuracy and spatial and temporal resolution. It is mainly for earthquake predication so most of the GPS observation stations are deployed along faults. In some areas the amount and distribution of GPS observation stations are not as desired. Hardy function interpolation, bi-cubic interpolation function have been used to intensify the GPS network, but the results are not so good. Finite element method and discontinuous deformation analysis are also introduced to simulate the velocity fields. Both the finite element method for continua and the discontinuous deformation analysis for block systems are special cases of numerical manifold method, which is a newly developed general numerical method based upon mathematical manifold. In numerical manifold method the cover displacement functions on individual cover are connected together to form a global displacement on the domain. In this paper Chuandian's crustal motion velocity field is simulated by numerical manifold method with GPS observations. The derived velocity field can well represent the continua and discontinuous zones of Chuandian.
This paper is on carrier heading determination with GPS attitude determination (equipment) and TPSs. Time synchronization equipment for GPS and TPSs is designed with the help of GPS PPS. Linear interpolation and filtering methods for static data and cubic interpolation and filtering methods for dynamic data are applied. The precision error of the combination model of GPS and TPSs is analyzed. Experimental results show that the heading precision is 30″ in static condition, while 2′ in dynamic condition. The model can help the vessel correct the zero error of navigation devices, reduce the time to prepare to sail, and can conduct the vessel to make harbour.
This paper proposes a new textured image segmentation algorithm which integrates wavelet transform and Gaussian mixture models. This algorithm includes pretreatment, wavelet transform, training, calculating posterior probability and labeling image. Some aspects are analyzed in order to use Gaussian mixture models in textured image segmentation problem. Experiments show that the algorithm can give an excellent segmentation result.
A new self-adaptive gradient is proposed for the detection of vague edges which is difficult to be detected according to traditional gradient. Based on the newly defined gradient, a new edge detecting algorithm is put forward. The edge detection result of test image shows that the new algorithm can improve the detecting rate of vague edges.
A M-band-wavelet-based features for progressive texture image retrieval method is presented. The information of a texture image is acquired through M-band wavelet decomposition of the original image. The integration of two feature descriptors, wavelet-coefficient standard deviation of the approximation sub-image and M-band wavelet histogram, and their corresponding distance similarity measure functions are used to realize progressive retrieval of target texture image databases. Finally, a texture database obtained from Bordatz album and USC image database is used to check the retrieval performance of the proposed method.
This paper applies the SOFM (self organized feature map of neural network) classification software, and choose the Landsat temporal TM images in Mays or Junes of 1988, 1994, 2001 and 2003 and applies the five forms of urban expansion identification model considering the ring roads. The results shows that infillment and expansion are the main forms in the three periods of urban growth process from 1988 to 2001, from 1994 to 2001 and from 2001 to 2003, while the linear branch and clustered branch are the main forms in the urban growth from 1994 to 2001 between the fifth and sixth ring roads.
On the basis of the combinational representation of spatial topological relations, the paper shows a further-perfected method for combinational reasoning with basic spatial topological relations. In addition, a spatial topological relations reasoning table is given, and a complete diagram about spatial topological relations between a line and an area is listed.
The detailed direction relations are proposed to describe the directions related to the interior of spatial objects, such as “east part of a polygon”, “east boundary of a polygon”, etc. Then this paper, integrates the detailed directions with exterior direction relations and topological relations and defines several NLSRs. Finally, based on the NLSRs, a natural spatial query language (NSQL) is formed to retrieve spatial data from spatial databases.
GIS cognition depends on people's understanding and cognition to map. GIS data organization, whose contents come from the real world, is one of the key and core problems on GIS. So, it is necessary to Abstact and describe the real world in order to make the real world expressed on the computer and to develop the practicable GIS. Certainly, geographic spatial cognition should be applied to the whole Abstact course. Consequently, we must reasonably organize the data on computer based on the cognitive theory during developing GIS.
This paper discusses the placement of Chinese annotation from point of view of graphics. Area Feature is classified as simple polygon, complex polygon and special polygon. For simple ones, annotations are placed along the longest edge. For complex ones, firstly the polygons are simplified according to close points, then the longest diagonal is gotten, lastly, annotations are placed along long-diagonal. For special ones ,the polygon is partitioned off several parts by a certain rule for getting its sub-diagonals, then its annotation is placed by means of the second.
For meeting the semantic demand of the spatial information grid and expanding the data types of computer grid, the ontology and LDAP (light weight directory access protocol) are combined to make a resource management system of spatial information grid. It can filtrate the nature of the local ontology systems to construct a virtual organization which can provides a global directory service. In conclusion, the semantic grid of spatial information system, which combines ontology and LDAP, can improve the ability of the integration and interoperability of spatial information grid
ccording to the fact of existing mapping relations between cartographic region and the subjective cognition structure, this paper brings forth the definitions of imitative map symbol and virtual map symbol, studies the rule of their evolution, puts foward the mathematical model for maps of planning and forecasting as well as the definition for geo-cyberspace.
On the basis of the analysis of denoising and edge detection of vehicle recognition, this paper proposes an effective detection method based on anti-symmetrical wavelet. The specific steps are illustrated. The results verify that this method improves the precision and the level of recognition.