2009 Vol. 34, No. 3
To quantitatively assess the differences born from rheological models on postseismic displacements and viscoelastic Coulomb stress changes,for 1997 Manyi earthquake after decay time from 1 year to 100 years when employing three linear rheological models,namely,Maxwellian model,standard linearsolid model,and Burges model.The results show that:① During transient phase,from 1 to 5 years after Manyi event,standard linearsolid model and Burges model are nearly the same as the other two ones.While during the later phase,starting from 10 years later,Maxwell element does and so are those with Maxwellian model and Burges one.② Similar is their influence on spatial pattern of viscoelastic Coulomb stress changes,though stress shadows and stress-triggering zones enlarge with time.Such tempo-spatial patterns of postseismic displacement field and viscoelastic Coulomb stress changes are consistent with the point that Burges rheological model is general compared with the other two.The uniqueness of rheological model should be figured out by a case-to-case study involving some kind of recursive determination of rhological model through multiple data sources such as GPS,InSAR,levelling,and those measured at different time-intervals so as to explain kinemics of displacement because of postseismic relaxation.
A clustering analysis method is used in the optimization of observed gravity data during the computation of local geoid.Two slopes of terrain data were used as criteria in order to find which data is more important according to the characteristics of gravity field.A numerical experiment was carried out in hill area.After half observed gravity data are deleted,the maximum variation of the geoid is 1.2 cm,the minimum is-0.4 cm,and the average variation is 0.3 cm.Compared with the result from non-deleted observed gravity data,the deleted data still works out acceptable results of similar precision.The numerical experiment validates the feasibility of the clustering analysis methods,which provides a new approach to optimize observed gravity data for computing local geoid.
We study TERCOM algorithm in gravity matching and analyze its adaptability.The experimental result shows that this algorithm can do precise matching easily.There is a significant correlation between coordinates error and roughness.It is gradient variance.Roughness and gradient variance are good indices to select matching areas.
By using 84 seismic moment tensors,collected from the Harvard centroid moment tensor between 1903 and 2003,and 214 GPS velocity observations,collected from the crustal motion observation network of China between 1998 and 2004,we fix the weight scaling factor of these two kinds of data in the joint inversion through Helmert method of variance components estimation(VCE),and invert for current crustal motion in Sichuan-Yunnan area.Meanwhile,on the basis of the analysis of inverted results,the following views are concluded.① By using VCE,the weight scaling factor of GPS observations with a value of 0.833 is higher than that of seismic data,with a value of 0.167.It shows the importance of GPS observations with high accuracy and relatively uniform distribution in joint inversion.② The crustal strain field in Sichuan-Yunnan area shows that the direction of compression strain is EW in the areas above 30°N and below 30°N,NE in the west of 100°E,and NW in the east of 100°E,which is accordance with other studies.
GPS has been widely used in geodetic measuring,retains coordinate system,and monitor global plates movement or regional crust deformation.We analyze and compare the effects of different reference models and systematic parameters on adjustment result.Compared with some schemas of adjusting the Xi'an land subsidence monitor network with systematic parameters and constrains,a lot of valuable findings are concluded.
The estimation errors leading by the observation noise and the data resolution are discussed.The general formula of optimal linear estimation and its error power spectrum that considering observation noise and data resolution are given based on the frequency form of the least mean square error criterion.The example shows that the estimation results are mainly affected by measurement noises when the data resolution is high.However,the aliased errors because of discete sampling are dominated in the estimation results when the data resolution is lower at some degree.Improving the quality of observations has a little effect on the improvement of the accuracy of estimation results.The findings can be a reference for the scheme design of gravity data sampling.
Expressions for the forward and inverse solution of Gauss and Mercator projections by complex numbers are given in this paper.Based on these expressions,direct and indirect formulas of the analytical transformation between Gauss and Mercator projections are derived.These formulae are symbolical forms which include the first eccentricity e of the reference ellipsoide.Hence,they can solve problems that deal with transformations between Gauss and Mercator projections when different reference ellipsoids are used.The numerical investigation shows that these formulas are sufficiently accurate up to 0.000 1 m and can satisfy practical applications.
We give two models of VMF1 and GMF derived from ECMWF data based on NMF model,present the space-time analysis of three mapping functions.A real example of ground-based GNSS retrieved water-vapor is given to demonstrate the accuracy of VMF1 and GMF models.It is shown that the application of VMF1 and GMF improves the precision of GNSS retrieved water-vapor.At the same time,many investigations may be concentrated on the repeat rate of baseline length,absolute changes of station heights,and the terrestrial reference frame.
The composition and technical characteristics of low altitude remote sensing system based on unmanned airship are introduced. The unmanned airship automated flies along the predefined routes and captures image sequences under the controlment of autopilot system. Geometric processing of captured low altitude stereo images, such as image matching, relative orientation, bundle block adjustment, panorama and orthoimage generation, are addressed in detail. Experimental results show that the developed system is qualified for high overlap and high resolution stereo imagery acquisition, and has good potential in large scale mapping and precise three dimensional reconstruction areas.
Quality assessment for remote sensing image compression is of great value in many realms.However,there has no quality assessment scenarios in the field of surveying and mapping.This paper suggested that remote sensing image quality assessment experiments centering on subjective assessment and objective assessment should be taken according to application requirements.The experiments show that the compression ratio should be no more than 4∶1 if the improved SPIHT algorithm were employed on board for Resources Satellite 3.
Based on the characteristics of roads on high-resolution remotely sensed imagery,a T-shaped template matching is proposed to track ribbon roads with much vehicles occlusion and shadow of colonnade on roads' edges.The T-shaped template matching integrates the merits of profile matching and template matching.Our tracker uses angular texture signature to locate the starting point and to measure the road width and road direction,and employs a T-shaped template matching to predict the sequential road points.It is proved a more robust semi-automatic road tracker.
A fuzzy ARTMAP model is proposed to solve the problem of sub-pixel mapping with the assumption of spatial dependence,based on the assumption of spatial dependence and the application of the soft classification result.The model was tested on synthetic TM image in Wuhan area.The result is compared with the result from BP,which shows that this method can efficiently resolve the problem of sub-pixel mapping.
A new method is proposed for automated recognzing the change types of residential areas using topological relations between new and old boundaries of residential areas.The residential areas samples on new rectified images are selected by existed boundary of residential areas on old maps.In order to obtain correct ranges of residential areas on the new rectified images,a two-step algorithm is applied.The first step is to do initial extraction of residential areas based on Law's Temples.The second step is to adjust the initial results using Grain table.To recognize the six change types of residential areas,the topology relations of new boundary on the rectified images and old boundary on the existed maps are analyzed by a 4-intersection model.The experimental results show that the proposed method using topology relations can automatically identify the change types of residential areas and provide more accurate change information.
The enormous volumes and valuable applications of MODIS multi-spectral images make it necessary to be compressed losslessly with effective methods.To solve this problem,an optimal linear prediction and band ordering are adopted to exploit abundant spectral redundancy,and SPIHT algorithm is used to eliminate the spatial redundancy of MODIS data.The optimal inter-band prediction sequence is specified by band ordering.Except the first band,only residual error images of other bands need to be encoded after band prediction.To avoid information loss,the optimal linear predictor is improved by rounding the prediction coefficients into integers.The experimental results show that our method has more compression capabilities.
We propose an adaptive clonal selection algorithm,which can adaptively set the mutation rate of each antibody according to its affinity and utilize the non-uniform mutation to decrease the complexity of the algorithm and computational costs.Experiments were performed to evaluate the performance of our proposed algorithm in comparison with other methods,genetic algorithm,simulated annealing algorithm,genetic simulated annealing algorithm.The results show that our proposed algorithm consistently outperforms the traditional algorithms.Compared with traditional CSA,our proposed algorithm can more quickly find the optimal solution and hence provides an effective solution.
To investigate the character extraction from complex background handwritten images,inertia quadrature,which is the second order statistic feature of gray level correlation matrix,is used for speckle reduction and foreground-background separation of document images,Hough transform is used for form frame line detection.The character extraction consists of line detection,speckle reduction,region growing,line removal,and broken stroke mending.The experimental results show that our proposed method is effective.
A real-time dynamic bleeding synthesis and simulation model based on computational fluid dynamics is proposed,which aims at realistic simulation of bleeding in the endoscopic surgical training systems based on virtual reality.Navier-Stokes equations are adopted to simulate blood flow as an incompressible fluid.A faster solution to Navier-Stokes equations is employed to solve the density field and velocity field in order to develop a real-time system.In light of this solution,a prototype of bleeding model with OpenGL was implemented.The results show that this method applied to the bleeding simulation is elucidating and practical.
A method to accelerate 3D texture-based volume rendering is proposed based on hierarchical bounding volumes(BVH).First,a post-classification 3D texture volume rendering is realized using GPU fragment shaders.Then,the original volume data is divided based on space position layer by layer according to the height of BVH tree.In each layer,the volumes corresponding to BVH tree nodes are subdivided into eight sub-volumes along three orthogonal coordinate axes.The bounding volumes are established for sub-volumes and the correlative information is stored in the corresponding BVH tree nodes.Finally,when rendering the volume by traversing BVH tree,information of BVH tree nodes is read for judging whether the corresponding sub-volume should be rendered or jumped.The experimental results show that good accelerating effects can be obtained when combining this method with 3D texture volume rendering based on GPU.
The traditional dynamic representation model has inhibited the increasing needs of 3D dynamic characteristics of house properties information,such as the multi-scale spatiotemporal features,diversity and asynchrony of partial changes in 3D space,high relevancy among change events.We propose a novel dynamic representation of 3D house property based on hierarchical events,which are characterized by land-block event,building event,storey event,unit event and property right event.The experimental results show that this representation is effective to model the detailed 3D dynamic change information of complex buildings and their related house properties.
We define a k-nearest feature based on co-location patterns,and develop k-nearest feature co-location mining(KNFCOM) algorithm to mine this kind of co-location patterns.The experimental results show that KNFCOM algorithm is efficient and scalable for mining spatial co-location patterns from various large spatial datasets.
Geographical area entities are different from geographical point entities,because they have both position feature and shape feature.It is not enough for geographical area entities to be clustered if the clustering criterion just considers distance factor.The clustering criterion designed by us includes distance factor and geometry shape similarity factor.On the basis of this,the corresponding clustering algorithm was implemented.The experimental results show that the algorithm fits to clustering analysis of geographical area entities.
An ontology knowledge representation model for spatial relation is established.Based on point set denotation of SRC-Ontology,arithmetic morphological operators is adopted,and a spatial topological relation widening representation method including 6 species,43 types of three basic spatial entities,namely points,lines,and areas,is proposed.This representation method not only wides SRC-Ontology's 8 topological relation representation method,and provides more explicit formalization representation for spatial relation ontology modeling,but also make the practical application possible.The experimental result proves the feasibilities and validity of the proposed method.
By analyzing the typical geo-spatial information flow process,we propose ward three GISMs: chain model based on linear transfer,star model based on co-construction,and sharing and net model based on Web2.0.The related spatial information applications for every model are also discussed.Moreover,we discuss the geo-spatial information value-added services network,which will be formed on the internet in the future,and the development and prospects of GIServices.The development mechanism of geo-spatial information service models is summarized.The application of geo-spatial information net model used in grid based GIS is also discussed.
One-dimensional river quality system dynamics model is applied to the water quality simulation and conceptual GIS-SD frame is constructed.Based on ComGIS and system dynamics model,the experimental system of water quality simulation in water pollution accident was developed.The Songhua River water pollution accident was taken as an example.The spatio-temporal change of nitrobenzene concentration is dynamically simulated.The results show that the simulation of spatio-temporal distribution of pollutant in water pollution accident,model regulation,scenario analysis can be realized.
We discover and define the order isomorphism characteristics of DEM,then point out that the order isomorphism characteristics of elevation is one of the most important theoretical problems of DEM.Based on it,we prove that the prerequisite qualifications of order isomorphism of DEM are the topological correspondence with ground during interpolation being generated.Moreover,we demonstrate that the order isomorphism characteristics of three main interpolation methods about DEM generation.
An improved algorithm of node refinement scheme called endpoint triangle's circumcircle method(ETCM) is proposed,which has a linear time complexity.Regarding stability,new nodes quantity,time costs and meshes quality as criterions,ETCM and several existing node refinement algorithms were evaluated by simulations.The results show that ETCM has the least time costs,and is more independent of data distribution.Moreover,the performances on other criterions of ETCM are almost the same as those of the best of existing algorithms.
The characteristics of existing approaches to the selection of streets are summarized based on an analysis of the literatures.The metric information,topological information and thematic information are calculated for street networks.From an artificial intelligence perspective,the generalization process can be seen as an optimization problem.A progressive approach to the selection of streets base on information loss is proposed.This approach minimizes the information loss.An experiment was conducted on a partial map of an urban settlement from the compilation specifications for 1∶25 000,1∶50 000 topographic maps.The Results show that our proposed approach can select the streets progressively and dynamically.
We apply support vector machine to simulate the relation between arable land area and datum of driving forces of land use change of Hubei Province from 1986-2004,and compare the test values by GA-SVM with ones by BP and RBF neural networks models.Practice proves the simulation results of land use change by SVM are more effective than those from BP-ANN,and is approximate to the precision of RBF-ANN.
By comparing with current methods,we propose forward a new urban land classification model based on k-order data field point to point-factors.This model has three key techniques links: on the layer's classification,the model provides more flexible policy and expresses the spatial distribution correlation of different class factors.Moreover,we desert the old classification method purely according to property.On the effect area division,we build k-factor influencing environmental effect area which has an advantage in no crack and no cover by k-order Voronoi polygon nearest neighborhood division.With k-factor influencing effect area,we can control model precision and meet the needs of Urban Land Classification in complicated conditions.On the calculation of assessing point effect value,we present a factor value calculating strategy corresponding to k-factor influencing environment,especially in three kinds of approximation as well as more kinds of multi-factor calculating rules.
A two-level taxonomy of slope positions is presented,and a fuzzy inference approach based on similarity to the typical locations to fulfilling the quantification of the spatial gradation between slope positions is proposed,which is normal phenomenon in nature.The new approach overcome a lot of some shortcomings(e.g.,neglecting spatial information) in current approaches to quantifying the spatial gradation of slope positions,and is applied to quantifying the spatial distribution of slope positions with a fuzzy manner.The results show that both the two-level taxonomy and our proposed approach are reasonable.