2009 Vol. 34, No. 2
LBS is an improvement of the development from a GIS to geo-spatial information services.Facing to the requirement of the geo-spatial information from the masses and the opportunity provided by next generation Internet and Web 2.0,a new mode of geo-spatial information services based on DMI was presented.Firstly,the concept of LBS and the chance of Web 2.0 were introduced.Then the characteristic of DMI was discussed.Taking Image City·Wuhan as an example,the function of geo-spatial urban information services based on real images was introduced.Finally,the feasibilities of its industrialization were discussed.
We proposed a practical model for water pollution accidents.The four-point implicit difference scheme was used to discretize the governing equations.Then a geographical information system(GIS) was employed to realize the real-time dynamic visualization of pollution simulating results on the ArcGIS platform.Finally,we employed the model in the public safety emergency platform with an example.The model shows simplicity,easy realization,high computing speed,high efficiency and good stability,and provids an effective assistant tool and decision-making foundation for water pollution accident emergency disposal with the intuitive and dynamic visualization of pollution information.
We a proposed a application-oriented model base system,in which objects or phenomenon and process are separately abstracted into descriptive models(DM) and operative models(OM) by object-oriented method.The concepts of model class and model instance were built respectively based on the analysis of relationship between DM and OM.The object-oriented abstraction,encapsulation and heritance mechanism was designed to make convenient for model application,maintenance and composition.The statistic model base system was designed and implemented successfully,and some common statistic analysis models were integrated in order to build a statistics model base system(Sta_MBS).
A urban municipal supervision and management grid system is implemented based on spatial databases.In this system,urban municipal supervision and management area is divided into many continuous anomalistic grids.The establishments in the grid are called components,and the accidents are called events.Then an appointed person will fully take charge of each grid area.The person should go the rounds and report in due course to the functionary once a paroxysmal event happens in the grid area.The grid plot is easy to draw with the ordinary cartography technology.While the whole grid system is hard to evaluate its suitability.Trying to achieve the evaluation,six variables and a model are presented.The six variables are: impactful area(A),time per patrol(T);short-time increase area(S);long-time increase area(L);grid comvex corner number(V);components occupancy percent(P).Based on the six variables,a hierarchical statistics model is built to achieve the evaluation.The model can find an idiographic statistic to show the suitability of a grid system.And the difference cities can be compared by the statistic.Finally,the model's maneuverability is proved by SPSS software and the material data is from Shenzhen urban municipal supervision grid division.The example shows that the hierarchical statistics model works well.
The realization of distributed geographic models sharing may strengthen the functions of GIS analysis,forecasting,decision-making and so on.But the existing distributed geography model resources have not yet realized global sharing.With the rapid development of information technology,the geographic model sharing via Internet has become not only possible,but also essential.We analyzed the present situation and existing problems in geographic models sharing and introduced a new method for distributed geographic models sharing based on Web Services,which is provided to locate,share,and publish model sources.We also defined Web Services for geographic models and its corresponding service framework,and service system in order to overcome the obstacles of model resources derived from the distributed environment.We constructed geographic models sharing gateway as a confirming platform.Experiments proved that the method for distributed geographic models sharing proposed here is practical and feasible based on Web Services.A user can locate,access,and retrieve all geographic models available in the architecture in an easy,flexible,and agile way through Web Services.
Many factors cause incorrect terrain modeling.The vital reason is the ambiguity of DEM quality concept.It causes the faulty for DEM accuracy assessment and the imprecise altitude interpolate model.Hence,perfecting fundamental theory of digital tertian modeling,improving on DEM processing technology and optimization of DEM data structure are key problems of high fidelity DEM establishment.An important basis is provided for high fidelity DEM establishment.
Computer technology,which has experienced 20 years rapid development under desktop-computing paradigm,is gestating one kind of innovatory computing paradigm:ubiquitous computing.Because of the requirement of mobility and location information,ubiquitous computing natively grafts on geographic information.Therefore,studying geographic information in a ubiquitous computing environment is necessary.The concepts and significances of ubiquitous space and ubiquitous geographic information were presented,and the framework of ubiquitous geographic information was established.Finally,we carried out detailed analysis on the components of the framework.
Based on an incremental insertion algorithm for creating of Delaunay triangulations,an improved algorithm of spatial raster index was introduced to judge which triangle the point was inserted in and triangle adjacency was fully used in triangle retrieval.We proposed a new idea for interpolating regular square grids.Experimental results show that the proposed algorithm for creating of Delaunay triangulations and interpolating regular square grid is more efficient.
A progressive representation model for street networks of vector data was presented based on the theory of plane Euclidean graph and abstract complex cell.Abstraction operator and refinement operator were used define the street elimination operator and street refinement operator.Topological consistency is implicit in the progressive representation model built on such operators.This model shows that the accumulation of changes and the execution of atomic operators that produce these changes both have sequences.A progressive generalization algorithm based on the ordered generalization tree structure was proposed.This algorithm brought both the map generalization knowledge and data structure.Hence,the generalization process can be implemented intelligently in such a way.
Digital watermarking algorithms for vector digital maps are an efficient method to counter abuses of the maps.We analyzed current methods of watermarking for digital vector geo-data and presented a new robust blind watermarking approach.The proposed algorithm starts with the area subdivision,then watermarking is embedded into length of vector by changing some x coordinates or y coordinates.The experiments show that the proposed algorithm could effectively resist the attack of noise,removing points,adding points,deleting points,and so on.
When using geo-spatial database and geographic information system,the volumes of map data to be loaded are hard to be estimated and the memory requisition is difficult to be allocated in advance.We proposed a new data scheduling method to solve the problem.The data exchange between memory and secondary storage devices was implemented according to fist in first out(FIFO) strategy in this method.The problem of large volume map data reading and displaying under fixed memory was solved efficiently.
Rapid urbanization area plays an important role in LUCC case study.Based on the reviewing of domestic literatures of LUCC driving forces,we used the Logistic model to analyze the construction land change driving forces of Longgang District of Shenzhen City.The results show that natural factors are key ones to restrict construction land expanding,and urban plan and economy factors are the most important factor in all of social-economic factors.Moreover,distances from urban roads effect the expanding of construction land mostly in location factors.
Land resources optimal allocation is one of the most challenging issues in land science field.Houlcuer the current optimal land use models have many deficiencies.We propose the land use optimal allocation model based on multi-object planning(MOP) and cellular automata(CA).Furthermore,Jiayu City was taken as an example to evaluate the model and to compare it with other models.The result shows that the integrated model based on MOP-CA has a better simulating effect.This integrated model realizs the unification of the quantitative structure and the spatial configuration optimal.
We detected the changes of roads in outdated vector map using updated RS image automatically and semi-automatically.The changes of roads in map can be described by two types: one is partial changed or diminished compared with updated RS image;the other is new.Based on the registration of RS images and road networks map,we detect the changes of the two types as follows: one is,based on old map road networks,partial changes or diminishes in roads are detceted on images automatically,buffer distance is defined and methods of multi-scale template matching and strategy of knowledge is developed in this process;the other is,based on RS images,new roads are extracted semi-automatically.The model of auto-initial-value LSB-Snake is developed to extract new added road for the purpose.Experiments indicate the methods can detect the changes of roads in outdated vector map effectively and automatically.
ADS40 images with high spatial resolution have many more spatial characteristics than low-resolution image except spectral characteristics.We introduced a object-oriented classification method based on multi-scale segmentation to classify ADS40 image of Taiyuan City.Firstly,the whole image is multi-scale segmented to get objects.Then,The features of objects,such as spectral,geometrical and topological characteristics,were measured.The hierarchical structure for classification was built.Finally,we applied a fuzzy rule classifier to extract the classification information of ADS40 images.The research shows that the object-oriented method can improve the overall classification accuracy of ADS40 images,reduce the Pepper and Salt' Pheomenon effectively,and meet the requirement of ADS40 images classification compared with classical classification approaches.
As a new type of aerial digital camera,the airborne three-line array sensor ADS40 now has been more and more popular in the acquisition of high-quality aerial imageries.The object-space back project calculation referring to image point coordinates calculation of the ground points plays a fundamental part in the processing of photogrammetry data.However,the best scanline search is the foremost issue for the object-space back project coordinates calculation algorithm of ADS40 imageries and has becomes the efficiency bottleneck of the current algorithms.We presented a novel object-space back project algorithm for ADS40 images based on central perspective plane of scanline.Experiments proved the feasibility and efficiency of the algorithm,which has currently been applied in the processing module of ADS40 imageries.
With single-temporal MODIS data of Gansu Province,we used a maximum likelihood method and decision tree methed based on data mining software See 5.0 to stuly the land cover classification.The experimental result shows that the accuracy of low vegetation area is improved with the indexes of TVA and TVD,compared with Maximum likelihood classfier,and data mining software See 5.0 is able to build decision tree quickly and improve the precision of miscible classes.
Laser scanner records measured distance,angle and reflected laser intensity by sending and receiving laser impulse.The distance and angle data are widely used to acquire point coordinates.However,laser intensity is not made full use in existing studies because of its uncertainty and instability.We presented a method for extracting and classifying building information based on a vehicle-borne laser scanning system.In this method,intensity is corrected according to different scanning angles and distances.Intensity is divided into certain levels,and this is used to show distributing curves of different objects and determine the peak values of curves.Experimental results show that different kinds of objects can be extracted and classified from the peak values.
According to single-view point cloud,we presented a multi-view metrical data registration method for the industrial sheetmetal part without texture.In the whole registration,the actual corresponding feature lines don't exist between the images as the feature line in every image is shifted because of the turning of rotational table.Therefore no actual corresponding points exist between the points cloud,which is computed for every model.The multi-view metrical data registration method was described based on the combination of the close absolute model network adjustment and iterative closest point algorithm.Experimental results show that the method is robust and valid.
Artificial circular targets are popularly used image features in computer vision and close-range photogrammetry applications.It is vital important to determine their elliptic projections in an accurate manner.A novel technique for accurately determining an ellipse center was presented.The technique,called the moment and curvature preserving(MCP),utilizes the first three intensity moments and the intensity gradient of the image for sub-pixel edge detection,then performs direct least squares fitting(LSF) for ellipse center location.
We mainly presented the modification of the cloud parameters in both temporal and spatial dimensions.The modification leads to a new drought monitoring model with a stable performance to variation of time and space of remote sensing data.This modification function was applied to regulate the 3 cloud impaction functions.Finally,we modified the new drought inspection model by evaluating different weights to the 3 cloud impaction functions.Meanwhile,we applied this new model to the FY-2C data covering the whole China.Compared with the traditional monitoring algorithms,the new model is proved to be capable of providing a more accurate and reliable result in large scale of time and space.
Remote sensing is able to provide the information of crop's growing way and an absence of water quickly,real-timely and in a large area,and make up the shortcoming of measurement in the field.We constructed a relevant statistic model for predicting crop water content based on shortwave angle slope Index(SASI),which uses the equivalent water thickness per unit area at canopy(EWTcanopy) receiving from global vegetation moisture index(GVMI).At the same time,the model was used to retrieve the water content of crop in Huanghuaihai plain in China.The result shows that the angle index model has strong correlation with EWTcanopy,and the water content of crop gets from it has good consistency with the relative moisture of soil at the same term.
Refractivity profiles observed by COSMIC(the constellation observing system for meteorology,ionosphere,and climate) GPS RO(radio occultation) mission were validated with global radiosonde soundings.The COSMIC RO events that occur within 2 h and 300 km of radiosonde soundings were gotten during the period from June 1 to June 30,2007 and more than 4 000 pairs of refractivity profiles were analyzed.The differences between the two types of refractivity profiles are the smallest in high latitude region and the largest in low lat-itude region.The same trend is also found in the comparisons between COSMIC RO and NCEP(National Centers for Environmental Prediction) refractivity profiles.We concluded that the precision of RO refractivity profiles is better in high latitude region than that of in low latitude region.There are systematic biases between RO and radiosonde refractivity pro-files in middle and low latitude region.No systematic bias can be found in the comparison be-tween the corresponding COSMIC RO and NCEP refractivity profiles.We deduced that the quality of radiosonde data could be the main reason for that bias.
In order to have a good understanding of the characteristic of time-domain frequency stability for the atomic clock,the effects of the main error sources on the time-domain frequency stability were studied,including measurement resolution uncertainty,phase steps and frequency spikes,leakage errors and end-of-data,and so on.The approximate formulas for the effects of the main error sources are deduced.The characteristics of the effects are also analyzed.Then the corresponding methods for reducing the error sources are given.The validity of the methods is verified using simulated data.
The influent factors,which should be considered in the analysis of X-ray pulsar visibility,were summarized.The calculation formulas of pulsar elevation angle and the shelter from the three-body were also presented.According to the requirement of navigation,fifty X-ray pulsars were selected based on the rules of pulsar selection.The change of visible pulsar number with position,time,height were analyzed through calculations.The change of visibility of a single pulsar in a single day and the shelter from sun and moon were studied.Finally,conclusion is drawn.
The direct computation with the high-degree gravity field model is time-consuming.We studied a method of fast simulation of GOCE satellite gravity gradient observations along the orbit with high-degree gravity field model.We proposed a method,which uses the gridding data from the gravity field model on the different height spherical surfaces to interpolate the points along the orbit.The numerical analysis results based on the comparison between the interpolated values and the ones from the direct evaluation with the spherical series expansion show that this method is rapid and valid.
We analyzed the difference between bidirectional filter and other methods of precise orbit determination(POD) for LEO using GPS.The theory of GPS-based orbit determination for LEO using bidirectional filter was deduced from satellite motion equation and LEO GPS zero-differential(ZD) phase observation equation.Two GRACE satellites orbits were computed using the software developed by our institute.We compared results with the orbits provided by JPL and independently validated with k-band ranging(KBR) data.We found that POD using bidirectional filter improves not only the accuracy of individual filter result at the beginning of the data arc evidently,but also the accuracy of orbits in the whole data arc.We also found that the method of GPS-based orbit determination for LEO using bidirectional filter is feasible and the orbits of GRACE computed by the software are at a level of better than 5 cm in radial,transverse and normal direction,respectively.
Based on the navigation theory of GPS/DR integrated system,a Kalman filtering model,which integrates the GPS original observation and dead-reckoning information,was presented.Then,we used it to deal with the GPS/DR original data.Experimental results indicats that even only two GPS satellites in view,the GPS observation can be used by this filtering model to improve the positioning precision of dead-reckoning system.
The normal equations of GPS single frequency rapid positioning are seriously ill-conditioned because of a few observational epochs,which causes the inversion of coefficient matrix of normal equations unstable.We converted the ill-conditioned normal equations of GPS rapid positioning into a function optimization problem,and used genetic algorithm to calculate parameters solutions,which avoided the inversion of coefficient matrix of normal equations and could approximately acquire best solutions.A method was developed,which use MSEM(mean square error matrix) matrix of biased estimation to determine the ambiguity search space and use GA(enetic algorithm) method combining with Lambda method to fix integer ambiguities.Experiment shows that the method can correctly fix integer ambiguities with a few several epochs.
Based on the conception of the matrix volume,we presented the definition of the orthogonal degree of the matrices,generalized and extended the determinant method mentioned above.As the orthogonal degree of the matrices was applied to the ill-conditioning problems diagnostics,it is applicable to any matrices,and overcomes the drawbacks of the determinant method.
We presented a novel method for forecasting landslide displacement based on phase space reconstruction and support vector machine.Firstly,based on the chaotic characteristics of landslide displacement time series,mutual information was used to compute the optimal time lag.Then,landslide displacement time series was decomposed into different frequency components through a wavelet transform.We adopted of Cao to compute the optimal embedding dimension of the decomposed series of each component.On the basis of this,phase space reconstruction is performed for each component.Different support vector machines were established to forecast each component.Finally,the predicted results of the components were reconstructed as the final prediction result by wavelet theory.The experimental result show that this method can effectively apply to landslide displacement prediction.