1997 Vol. 22, No. 3
This paper discusses the characteristics of GIS,analyzes the problems existing in the development of GIS system.Based on the theory and practice of software engineering,a paradigm is designed,which is suitable for the development of GIS system.
The lack of compressive theory and formal description methods about 3D spatial features and their topological properties have been a major impediment to practical 3D spatial data model implementation. This paper focused on the research of a topological model based on space partition for 3D GIS. In terms of point-set topology and combination topology, the formal definition of 3D spatial features are described as orientable n-pseudomanifolds(0≤n≤3),and it can be represented by complexes which is the union of same or lower simplexes. From the number of important topological properties of n-pseudomanifolds and continuous map about homeomorphism and homotopy, the topological properties such as space partition, orientability, connectivity and Euler characteristic are determined. According to the formal description of simplexes and complexes, the formal framework of 3D spatial features is presented.
Because the original nine-intersection model for describing spatial relation can't describe ordering relation and adjacency,it is expanded by replacing the object's complement with object's influence range.The new frame for describing spatial relation is introduced.After that, the characters of new intersection model are given.
This paper provides a review of research on uncertainties in geographical information systems(GISs).This is followed by a description of a new method for deriving X-error band models based on the concepts of fields and fuzzy sets.A case study on a suburban land cover mapping confirmed that the proposed method is both theoretically sound and empirically efficient.The new strategy adopted in this paper will be beneficial for further systematic research on GIS uncertainties.
By analyzing the spatio-temporal process of land subdivision, this thesis sums up the properties of spatio-overlap and time-meet of temporal land parcels, summarizes the spatio constriants and temporal constriants of querying this type of parcels. Based on the extended space-time composite model and tuple time stamp, algorithms that query the chain of spatio-temporal of land subdivision are designed in term of the condition of constriants.
In order to model and represent the spatio-temporal processs of land subdivision, a spatio-temporal data model concerning temporal objects is designed in this paper. With the help of three tables:active land parcel, non-active land parcel and future index, and spatio-temporal data of land parcels are maintained in the land-related database and can be accessed by the users even after the land parcels completed their functions. In addition, time is added at two levels:at tuple level and at attribute level.
In this paper, some basic ideas of designing a spatio-temporal data model have been presented from two aspects of storage management and description of spatio-temporal semantics. Meanwhile, spatio-temporal object types and its data structure,spatio tempoal operators about an object-oriented spatio-temporal data model has also been presented.
Based on the test of hypothesis,inner and outer reliability are given from the predicted residuals of Kalman filtering.In the meanwhile,the departing estimation algorithm of model biases is also presented.A software performing the algorithm is developed to test the moving vehicles data of WAPGPS.Some conclusions in processing the dynamic data of WADGPS are obtained.
This paper presents a new approach to detecting man-made object changes in urban area. This approach is more automatic, precise and reliable than the conventional change detection approach, which were mainly used for the analysis of space-borne remote sensing image. The experiment results indicate the effectiveness and reliability of the approach.
A compression method of keeping match consistency on remote sensing image is represented. A lot of results of experiments are presented. The results describe the relation between image compression and match. At the same time, conclusion is drawn that for aerial remote sensing image at 25 μm resolution, when the compression ratio is 8:1,match consistency is kept.
In this paper, a new method for classification of multisource data is proposed. The images formation model, contextual model and reliability factors are taken into account in the method. The performance of the method is evaluated by fusing Landsat TM images and SAR image for land-use classification. Significant improvements in classification accuracy compared to the SAR image classifier are obtained. So it is an effective and robust method for multisource classification of remotly sensed data.
The method for the evaluation of flood disaster damage based on remote sensing is discussed. The remote sensing and geographic information system are combined to analyze the damage situation and derive the necessary information such as the submerged area and volume. Finally the derived information is used for the estimation of the crop (rice) yield decrease. The experiment is completed on REDAS/Imagine and ARC/INFO software systems.
China's coastal lowlands are easily endangered by flood and waterlogging because of the low and flat relief, the concentrated precipitation during the aestival period, and much more water coming from the upper and middle parts of rivers. Taking the coastal lowlands of Jiangsu province as an example, this paper creates a measure model to describe the inundation strength, and furthermore to analyze the significance of disaster mitigation.
Most of recent researchers believe that a lack of awareness and problems of accessibility to spatial data are significant bottlenecks to increasing numbers of users and applications.It is not easy for users to get spatial attribute from image of WWW Geographic Information System(WWW GIS).The image which users have received from server side,has no spatial attribute features and can not be operated easily.In order to solve this problem,the vector graphic seamless link with main database model for WWW GIS with Java and JDBC has been developed.With this model,users may be easy to operate WWW GIS,including pan,zoom,query and analysis.In client side,users operate the GIS like that in server side,and seamless link with main database.
The design and implementation of a symbol base, by object-oriented approach in thematic mapping, is introduced. Then organization of the symbol base, symbol classification and how to develop a symbol base by the user are discussed. Finally,a brief summary about the symbol designing thoughts is presented.
In this paper many primary problems and key techniques are analyzed and discussed on establishing remotely sensed image database,including structure form of image database,extended RDB,seamless mosaicking,generation of orthoimage,data compression,etc.
Today the open network systematic structure is an important direction of network development. The conventional network computer model has gained a tremendous changes with the development of computer network technology. The traditional centralized processing is transforming into the distributed processing. Distributed networking computing will be a main stream.
To make full use of GPS fiducial stations and to adapt them to multipurpose applicaitons such as geodesy, WADGPS, geodynamics and etc., with the aim of resolving the basic problem regarding the adaptability of GPS fiducial stations, this paper employs an orthogonal fitting approach to forming equivalent observations in real time with optional sample rates. Practical tests show that the algorithm is steady and ideal.