2009 Vol. 34, No. 1
Intelligent spatial information service is one of the most important area in GIS application and servici,grid based GIS is the key technology for intelligent spatial information service.In grid spatial information service,node is the basic cell of grid spatial information service system.Node construction researching is classify and manage the spatial information resources and GIS software component used to operate spatial information resource.According to the characters of intelligent spatial information system,we classified the spatial information service node as portal node,manage node,spatial information service node and function service node,and discuss the construction of each node.In the end we test the node construct method in an application system,make a conclusion and the future research areas.
By using digital photogrammetry method,A Yuan Dynasty blue-and-white porcelain is reconstructed.Based the profile of object in photos,and the manufacturing technology of porcelain,using a method similar as profile scanning,the accurate profile in multi photo as the constraint,the parameters of object are calculated by using the least square iteration.The best texture range in every photo is selected and the merge line is removed for texture mapping.The result of 3D reconstruction shows that the method is of high accuracy,high reality,and high automaticity.
A new unsupervised texture segmentation method is proposed by using Gabor wavelet.Compared to the classic one,we add Gabor scale relationships and space constraints features to the multi-scale features.In order to find prominent features for segmentation,texture features are integrated by independent component analysis(ICA).The effectiveness of the proposed method is demonstrated by using a set of images from the Brodatz texture album.
In order to reconstructing an ancient tomb of Eastern Han Dynasty,this paper transforms 3D polygonization into 2D situation taking use of the correspondence of 2D picture points and 3D points,and selects generating range,seed point by hand to calculate the difference of sets,determines generating range,maintains the seamless contiguity of TIN,and at last makes the surface model successfully.The authors also make an experiment on a vase and get a good result.
A kernel-based change detection approach in remote sensing images is presented.This algorithm detects change by comparing the probability density(PD) of the feature vector of bi-temporal images.The PD comparison is expressed as kernel functions;and change is detected using a kernel-based similarity measuring.PD is compared by defined kernel functions without PD estimation.
A roof detection method using LiDAR data is proposed based on points' normal with weight.The normal of the plane,which is composed of point and its neighbor points,is counted to find out the high frequency,and the roofs are detected.Each point's weight is considered to determine the contribution to the plane which diminishes the affection of noises to some extent,and increases the accuracy of the small roof detection.In addition,multiple thresholds are adopted to detect roof planes with different sizes.Experiments are given to prove the algorithm proposed.
Based on the traditional single-stereo VLL matching algorithm,MVLL,which is a multi-view image matching algorithm appropriate for the matching of linear-array images,is proposed.MVLL algorithm can integrate the information of multiple overlapping images to avoid blind information area,and thus has a high successful matching rate.Algorithm analysis and experimental results show that,compared with traditional single stereo image matching algorithms,MVLL algorithm can achieve prominent performance in the matching of both similar features and occluded features.
A target detection method based on multi-aperture SAR images is proposed.With this method the magnitude and the phase characteristics of SAR images were jointly used to distinguish artificial target from clutter.A number of sub-aperture images are generated from SAR image.As the energy of artificial target usually masses in partial range of azimuth angle,the local correlation between the sub-aperture images which are corresponding to the partial range of azimuth angle is strong in the presence of targets.So,the use of the coherence between these sub-aperture images is proposed for target detection.Experimental results demonstrate that the proposed method enhances the detection rate and reduces the false alarm rate effectively.
Weak edges are similar to the background in intensity which causes small gradient value.The previous edge extraction algorithms are difficult in detecting weak edges with tight threshold,while with loose threshold will lead to lots of false edges caused by noise and interference.An edge extraction algorithm based on linear features perception is proposed.The visual mode of linear perception is used as reference;and weak edges are selected according to their linear distribution.The experiment results show that the proposed algorithm has a significant enhanced ability to extract weak edges and inhibit false edges comparing with Edison edge extraction algorithm.
Existing classification methods,based on the homogeneous-region,mostly involve the best segmentation criterion choice.Using the so-called best-scale to classify the multi-scale objects defined by human subjectivity,the paper doesn't think it is the best way for classification.So the paper proposes a new multi-scale homogeneous-region model,fully using the longitudinal information which the homogeneous-region model provides,and adopting the scale-span classification method based on decision tree to improve the accuracy,without selecting the best-scale data.The result shows this method can distinguish objects accurately and improve the precision than sole scale classification.
A new method of digital close-range photogrammetry——panning and multi-baseline digital close-range photogrammetry,is presented.This method enlarges the intersection angle and improves the intersection precision by multi-baseline photography;enlarges the angle of view by panning photography,and resolves the difficulty of matching for images with large intersection angle.At the same time,this method applies the classic aerotriangulation and bundle adjustment to the close-range photogrammetry;we need more than three ground control points to compute the exterior orientation elements of all images.The experiments prove that this method can acquire the high accuracy and improves the production efficiency.
The measure of adjacent space's distribution researches into objects' distribution in adjacent space.It is the important basis of geographic analysis,environmental assessment,also location optimization.A Voronoi-diagram based method to measure adjacent spatial distribution is proposed,which dynamically determines the related extent according to measure point's Voronoi adjacent relation,and assesses the adjacent space's distribution based on the index of adjacent distribution.The method can measure any point's adjacent distribution.Furthermore,it can be used to evaluate the dispersion degree at overall level.Finally,an applied example evaluating the development of building lots and landscape protection is given to illustrate the application prospects.
The study of three dimensional geological modeling is a very important topic.Discussing the modeling principle and the advantages and disadvantages of 3D OO-solid model,primitives of OO-solid model,such as node(cru-node,inner-node,isolated-node,reference-node,interpolated-node,and feature-node),arc(feature line),polygon,region,component face(polygon face,component side face,component up-down face) and component,were modified.Conceptual model and logical model of OO-solid model are redesigned.Above research not only benefits muti-source data modeling,upgrades auto-modeling,facilitates dynastic updating of geological model,also favors seamless integrating with other models,such as TIN.In addition,used the methods which integrated object-oriented with set,primitives of OO-solid model and the spatial objects,such as point,line,surface,volume which including simple volume,complex volume,composite volume,were strictly defined and formally described from the topology.
A multidimensional and animated visualization system is proposed;and the significance key techniques,design and implementation of the system are described.Then an application to typhoon is given to explain the functions of the system.At last,the prospects of the system are discussed.
A raster algorithm of minimum spanning tree in space with obstacles is described.Firstly,with the idea of zero initialization,location data,including entity point,obstacle point and ordinary spatial point,are initialized.Secondly,the nearest connected graph in space with obstacles,also known as the Delaunay graph,is gained by trace back algorithm on the basis of Voronoi graph.Lastly,minimum spanning tree is gained by greedy strategy according to the nearest connected graph.
A view-dependent and real-time LOD algorithm is presented,based on the algorithm of surface units in high accuracy surface model(HASM).The grid data in DEM is divided into patches and organized in surface units.In the process of reconstruction of the virtual terrain for DEM,the surface units are interpolated at intervals in proportional to the distance between the units and the view point so that the LOD in the field of vision is produced in real time.The dynamic DEM data delamination and the scene of 3D virtual terrain are implemented by the method to reduce the consumption of system memory without building the hierarchical model for the regular grid DEM data.
This paper used the description frame of two regions with holes which was put forward by egenhofer,based on the 4ID,put forward a new extended model 4-4ID,which can describe the regions with a hole's special topological relations.At the same time,this paper presented the topological relations between simple regions and regions with a hole.
The inner core super rotation(ICSR) rate is 0.27°~0.53°/a,which gives rise to the annual average variation intensity about 0.08~0.16 μGal.Besides seismic data,temporary gravity data might become an important information source for detecting(ICSR).The influences caused by the tide,air pressure,polar motion and variation of the length of day,are drawn out from the gravity data recorded by the superconducting gravimeter(SG) at Jiufeng Station,Wuhan;and corrected temporary gravity signals are obtained.These temporary gravity signals are further analyzed by wavelet approach;and some valuble results are drawn out.Concerning the difficulties existed in detecting ICSR using SG data,some comments and proposals are provided.
Since there are many problems using traditional anti-jamming methods in hardware receiver,such as high cost,big system,high power and environment constraint,two methods are proposed based on software GPS receiver,one is time domain filtering algorithm based on subspace technique and the other is frequency domain filtering algorithm in which the extended extrapolation algorithm is proposed to avoid signal distorted due to component of jamming signal frequency zero set,and the estimated signal within the interference band are acquired after extended extrapolating.The experimental results show these two algorithms all can remove interference effectively and reliably;and frequency domain filtering algorithm based on extended extrapolation is better than time domain filtering algorithm.
The IAU2000 resolution was adopted at the IAU 24th General Assembly in 2000.The new resolution has officially become effective since January 1,2003.Compared with the old system(FK5),which was essentially derived from Newtonian Mechanics;the new system is kinematically defined by the position of the extragalactic radiosources.The two systems are mainly differenced in the definition of the pole,orientation and the models of transformation between celestial frame and terrestrial frame.As a matter of fact,implementing of the new resolution will affect the orbits of artificial satellites,whose trajectories are determined according to the ground observations.The paper describes in detail the impact on GPS orbits due to the introduction of the new models in IAU2000 resolution.GPS data on DOY 186 2005 are analyzed to find out the orbit difference between old and new models.Results show that orbits difference of GPS exhibit a periodical signal in either inertial systems or terrestrial frame,with an amplitude about 2.5 m at X,Z axis and 1 m at Y axis in inertial systems,while that is about 4mm in each axis in terrestrial system.Statistics of orbits difference show that the 3D RMS of orbits difference in inertial systems is around 3m,and the orbits difference is neglect able in terrestrial system.
Terrestrial laser scanning technology has been found a widely application on shape surveying,but its application to langdslide monitoring is tentative.The theory and method of fusion with digital image and scanning data are discussed.The perfect results showed that we can obtain more comprehensive geometric information on landslide surface Soas to provide more foundation for deformation analysis and interpretation.
The method of GPS satellite precise clock estimation is investigated and the contribution of pseudorange and phase measurements in GPS satellite precise clock estimation is analyzed.Based on the PANDA software,about 40 IGS stations are used to estimate the GPS precise clock.The results indicate that the difference of the PANDA clock results from the IGS finial precise clock products is better than 0.2ns,which is the same accuracy level of all IGS analysis centers.
Based on the demand of relative positioning in formation flying missions,the dynamic observation geometry between the global navigation satellite systems and the formation flying satellites is analyzed.The description of relative dilution of precision(RDOP) and its properties are illustrated.The geometric dilution of precision(GDOP) analysis is carried out firstly for a single satellite in the formation.The common visible satellites and the corresponding visible time intervals were then discussed with different formation relative distances.The RDOP for formation flying satellites in certain scenarios is calculated and compared with the values of PDOP.Simulations show that the masking elevation angle of the receivers is a vital factor for GDOP.The formation relative distance has an impact on the selection of common visible satellites.The integrated GPS-Galileo system has advantages over the single GPS navigation system for the relative positioning of formation flying satellites.The former possesses a smaller GDOP value and thus can benefit the high precision inter-satellite position determination.
A new method that calculates ambiguities in GPS short-baseline through the combination with different carrier phase observations when the deformation is relatively large(0.7 m).A condition that should be satisfied to make sure that the ambiguities of L1 carrier phase and L2 carrier phase are integer,is also drived.The DC algorithm proposed in the reference \ can not only be used to large deformation,but also to the ambiguity resolution in GPS short baseline.Furthermore,the difficulty of the quickness and effectiveness of ambiguity resolution in GPS short baseline,is solved.
Many experiments have shown that zenith integrated precipitable water vapor(PWV) can be readily obtained with better than 2 mm absolute accuracy using GPS instruments.However,PWV measurements do not provide any information on the spatial distribution of water vapor.The measurements of slant precipitable water vapor(SWV) along each path contain much information which has the potential to be useful for numerical weather prediction.In order to get precise SWV,firstly the principle of remote sensing of SWV and computed diagram are described;secondly improved algorithm of converting double-differenced residuals to zero-differenced residuals is developed;finally a real example is given to demonstrate the algorithm involved using GPS and WVR data at one site.It is shown that the improved algorithm can be used to estimate SWV and the root-mean square error is less than 4mm between GPS and SWV.The accurately estimated SWV can be used to retrieve the three dimensional information of water vapor which is useful for numerical weather prediction,geodetic surveying and interferometer synthetic aperture radar(InSAR).
Considering the peculiar characteristic of indoor environment,based on specific hardware design which can insure the pseudolites clock synchronization,a precise point positioning model based on improved time-satellites difference for indoor pseudolites is proposed.Computation process of this model is described.At the end,results indicate that the use of 1 000 s static data span can provide a horizontal positioning accuracy at centimeter level in case of no cycle slip.
The wavelet approach for multiple decomposition of gravity anomalies is modified using multiscale edge analysis theory,and a separation method based on multiscale edges is proposed.The experimental results show that the new method has the same advantages of multiple decomposition method,and can be used to simultaneously perform vertical and lateral separation of anomalies.A proper degree for decomposition can be determined according to the distribution of multiscale edges of each source with respect to the scale,it is very useful to isolate single anomaly.Shipborne gravity data in southwest of Ryukyu subduction zone are analyzed.The result has good coherence with the geological tectonics in this area.
Local Geoid with high precision has important practical values.In this paper both the design and realization of the unitary frame and the detailed modules as components of the system are given in order to determine the local Geoid with high precision.Based on this,the systematic software is developed as a tool to process the gravimetric data automatically.As an example,this set of software is applied in certain area to practically calculate its local Geoid.It's proved in the practical use that this software can greatly improve the data processing efficiency and is helpful to standardize the calculation process of local Geoid with high precision.
In the rapid GPS positioning with carrier phase observations,the coordinate parameters and ambiguity parameters are highly correlated so that the float ambiguities resolved by least squares method are seriously biased.Therefore,it is difficult to correctly fix ambiguities.However,in the real applications,the various constraints exist in the coordinates or(and) ambiguities parameters.The constraints for coordinates can always be used to resolve float ambiguities with higher accuracy and the constraints for integer ambiguities can be employed to efficiently search ambiguities.Firstly,the general forms of constraint equations for coordinates and integer ambiguities are given;and the general solution is also derived.Each constraint equation for specialized situation is ulteriorly discussed in detail.At last,the numerical examples are implemented;and the results indicate that most of combinations of ambiguities can be rejected based on these constraints;and consequently success rate and efficiency of ambiguity resolution can be significantly improved.Therefore,the constraints should be fully used in GPS positioning.
An improved classification algorithm is proposed to deal with polarimetric synthetic aperture radar(POLSAR) images.This algorithm is based on a four-component scattering model,compared to the three-component(surface,double-bounce and volume) model introduced by Freeman and Durden,the four-component scattering model introduces the helix scattering as its fourth component,which can describe complex terrains and man-made targets in urban areas;so the four-component scattering model can deal with general scattering cases.In addition,this algorithm emphasizes the existence of pixels with mixed scattering mechanism,and applies the result of the four-component decomposition as feature vector to initial merging and the final iterative classifier.We use L-band AIRSAR data to demonstrate this improved method;and the experimental result verifies the effectiveness of this improved algorithm.