The Study Of Key Technologies For Permanent Basic Farmland Delimit Based On GIS

With the rapid development of urbanization and industrialization in China in recent years, the population gravitates towards the city dramatically and the city areas increase greatly. Generally speaking, urban expansion area also is also a good choice for agriculture which makes a contradiction between arable land and urban development. A large number of arable land is occupied for building land which threatens the safety of grain production. In order to ensure food safety and promote stability and sustainability of the national economy and the ecological environment, the national government made a resolution in strategic perspective to protect the basic area of farmland permanently. As an important way to ensure the safety of grain production, protecting basic area of farmland permanently is under delimitation currently which may not only help national government control the overall resource situation of the country, but also guarantee rational use of land resources and promote scientific and intensive use of urban land resource.Fuling District, located in the East Parallel Valley of Sichuan Basin ridge, is typical mountainous and hilly area, and is also the hinterland of the Three Gorges Reservoir Area. With some high quality arable land is drowned by Water storage in the Three Gorges Project and the construction of the new district and expansion of towns, the protection of arable land is much harder. However, this region which is an important food and cash crops output base is an important area for economic development in Chongqing, so it is necessary to strengthen the protection of arable land resources and scientific rational use of land resources. That means we not only need to pay attention to the quantity of arable land resources but also need to know the quality of it clearly, and from the macroeconomic development perspective to allocate the farmland resources of this region scientifically and rationally. The existing researches always focus on qualitative study including raster data analysis method all the time which can not reflect the quantity and quality changes of farmland clearly.In this paper, Fuling District, Chongqing City is used as a example. Firstly, mathematical quantification method including quantitative land evaluation and site assessment (LESA) method, the Delphi method, the analytic hierarchy process(AHP), maximum entropy techniques and TOPSIS order method, based on GIS methods and techniques for data integration, are all used to to select optimal layout of basic area of permanent farmland. Taking arable land delineation from second land survey data as research units. Secondly, using the professional GIS software ArcGIS to build a graphical models to construct basic area of permanent farmland database and making some studies rely on some other professional GIS software for data processing and output outcomes. Some basic area of farmland thematic map researches have been made by ArcMAP. Details as follow.(1) Exploring the significance of delineating basic area of permanent farmland considering geographic and geomorphic conditions of Fuling District and analyzing the current situation of farmland in the region from four aspects:distribution, quantity, quality and the problems of arable farmland. Then discussing evaluation factors for selecting an optimal scheme of basic area of permanent farmland, to provide a foundation for scientific and rational delineation of basic area of permanent farmland.(2) Obtaining the evaluation factors by GIS spatial data integration method and then standardizing them. Getting a comprehensive evaluation index weight by maximum entropy technology method and AHP method and building a system of selecting an optimal scheme of basic area of permanent farmland to make a standardized decision matrix. Using TOPSIS to sort all arable land index, through the index comparison, accumulate the number of permanent arable farmland to the basic farmland requirement and then export the result picture.(3)According to the function of graphical modeling of ArcGIS and permanent basic farmland evaluation results, a permanent basic farmland database is built. Graphic modeling can ensure data loading much more convenient and automatic. This is also a quick and easy method of sharing data and providing technical support for data storage.(4)The implementation of protective measures should be established by protective signs and responsibility agreements of protection. The establishment of protective signs relies on GIS’s spatial analysis function by giving some suggestions about the location of signs. The implementation of responsibility agreements of protection need farmers’ information and the basic function of WORD to ensure a rapid data input.(5)According to protecting data of permanent basic farmland, some studies of permanent basic farmland thematic map have been made. The studies mainly about the surface configuration, surface finishing and giving some analyzing support for key elements technical realization.The study results showed that: (1) The delineation of permanent basic farmland mainly located in west Wujiang and northern regions in Fuling District., for the terrain is relatively flat and it is the main area of permanent basic farmland delineation.(2) Through fully considering quality assessment factor of permanent farmland, the standard of American Land Quality Evaluation System (LESA) which has high public trust, and the result of TOPSIS sort, we found that high quality farmland mainly spread in coastal area of the Yangtze River, along the main traffic arteries and around the construction area of towns. Compared with other projects this project is more convenient for farmland selection.(3)This study select the relevant professional GIS software and graphical modeling function of ArcGIS for basic farmland database construction, compared with fixed software this integrating data can be relatively easy, saving cost, tools modification more flexible and customizable,diversify-cation and flexibility.(4)The farmland protection symbol established on many factors, including using the GIS spatial analysis methods to determine the comprehensive area for pennanent basic farmland protection signs to ensure the judgment for the position of protective signs more scientific; merging protective signs and mail by taking peasant information table as a data source to ensure letters of responsibility more accuracy and efficiency.(5)After the discussion of thematic mapping, the author shows that we should take full account of the complement and accuracy of various elements and mathematical representation method to improve the quality of thematic mapping and to make map elements being represented more complete and visual. Discussing from elements of parts to provide a more intuitive and comprehensive approach for thematic map production.