| Farmland suitability evaluation is one type of land suitability evaluation. It provides a direct reference to macrocosmic management and microcosmic control of agricultural production, and has important value to sustainable development of agriculture and national economy. Concequently, it's necessary to reinforce the study of farmland suitability evaluation. But traditional farmland suitability evaluation has problems that its results subjectively and its work wastes time and energy. In the other hand, farmland is a complicated system, land information is related to spatial location, and land suitability evaluation is also connected to half-construction issues. As a result, the technologies of geographic information system and decision support system are synthesized in land suitability evaluation. Spatial decision support system bases on geographic information system and decision support system, and can solve problems related to space. But study of spatial decision support system is just beginning, and its theory, method and technology need to improve. It's lack of study on spatial decision support system in connection with farmland suitability evaluation. Therefore, it's necessary to penetrate into such study.The paper studies on the components and their realization of farmland suitability evaluation spatial support system (FSESDSS), probe into all methods and their suitable area used in land suitability evaluation. Then, a FSESDSS is established basing on ArcGIS 9 and ArcObject components using Visual Basic 6.0. Its reliability and applicability are testified in farmland suitability evaluation in a county area. There are 7 chapters in the paper, and can be devided into four parts. The first is the theory bases of FSESDSS; the second part is the designation, development and realization of FSESDSS; the third part is the application of FSESDSS; the forth part is the conclusion and prospect.The first part is composed of three chapters. The need of study on FSESDSS was analyzed, and the theoretical and technological basis of FSESDSS was discussed. Chapter 1 is introduction. The research objects and content, method and technologic route were presented on the base of reaearch background and significance. Chapter 2 is literature summarizing. The trends of land suitability evaluation research are analyzed from three aspects: its content, its methods and the application of modern technology. The content of evaluation becomes extensive; quantitative methods of land suitability evaluation are developed; then, geographic information system is broadly used in land suitability evaluation and has trends of synthesizing with other technology. The weakness of previously study is briefly conmmented, so that the base of this study is made clear. Chapter 3 is the theory and technology that related to FSESDSS. Firstly, the principke of farmland suitability evaluation and technology of spatial decision support system are recommended, following with spatial decision support needs of farmland suitability evaluation. All of the above studies provide the theoretical and technology foundation for design and realize the FSESDSS.The second part is composed of two chapters. A FSESDSS is realized after designation. Chapter 4 is designation of FSESDSS. It has four components: database, model base, knowledge base and interface, and each has its function. The database is designed based on Geodatabase models. The types of system models is discussed, which are expressed by developing components. The evaluation knowledge is distinguished into regulation knowledge and static knowledge. The former is expressed by production regulation, and a reasoning machine completes its transference. The latter is handled by Words whose function established by VBA. Then VB is used to develop programs based on Arcobjects, arrange menus of ArcGIS, and form the system interface. Lastly, the system is integrated by ADO interface. Chapter 5 is the development and realization of FSESDSS. The software and hardware circumstance are provided. Models and knowledge are developed basing on ArcGIS and Arcobjects, and the transference of static knowledge is realized. The interface and dialogue box are established, and the menu function are detailed. After determination of database projection and the way accessing data, the system database is established using Arccatalog.The third part is Chapter 6, which is the application of FSESDSS. The system is used in farmland suitability evaluation of Fengqiu County, Henan Province, to study the suitability degree of paddy, wheat, and maize planting. The study of soil nutrients spatial distribution is fulfilled by using kriging analyse. The land units, the factors and their weights, the factors' marks, and total marks and grades of the units are determined. The results are reported through land suitability grades maps and tables, providing the reference to rural production structure regulation and land use planning of the county.The forth part is Chapter 7,which is the conclusion and prospect. The main content of the system are concluded, as well its performance in application. The aspects of future work were pointed out.A FSESDSS is realized according to above study:(1) A personal geographic database -farmland suitability evaluation database is established using Geodatabase at the help of Arccatalog;(2) Models of farmland suitability evaluation are developed using technique of ArcObject components, and stored in model base. It can be completed that the choice, transference and integratation of models when cooperation with knowledge base and interface.(3) Knowdge of farmland suitability evaluation is classfied into regulation knowledge and static knowledge, and expressed using different ways. A reasoning machine completes transference of regulation knowledge, while programs of static knowledge.(4) In addition to display, select, statistics and export maps and attributes, the interface of FSESDSS provides model choise, data admit, knowledge inquiring and other function using dialog.(5) Data visit of model and knowledge is fulfilled by means of ADO interface, and the components' function completed in DLL.Although it is successfully applied in farmland suitability evaluation in Fengqiu county, the system models are not enough, and the knowledge base needs improving too.
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