| Sustainable development has become a fucos matter in the whole world, a variaty of study items is being put in practice. Crop land is the basis of agriculure produce, and which is not a regenerative resourse. It is very important how to make use of and protect it effectively to our coutry, which has many people and little crop land. On the one hand, a lot of high qulity crop lands have been occupied as a result of city expanding, on the other hand, water and soil have been eroding as a result of unreasonable exploitation, zoology environment has beening destroyed. So the work of class assessement of crop land is the premise of reasonable utilizing. The blue print of land use will be according as The assessment result, on the one hand , the excellent land will be proctected, on the other hand, the crop land, which bring to erode of water and soil, will be resume forest.Geographic Information System (GIS) is a wholly new advanced spatial technique, which took its place in 1960s and has been developing swiftly and violently with the development of computer technolgy. So far, it has been applied in almost all areas dealing with geographical or spatial information. A study on the class assessement of crop land has important theory and practice value. It can afford fast,handy and exact information for the land management department because the capablity of linking the spatial data and attribute data.This resarch was conducted at chengguan town in xianju county of zhejiang province. With the support of ArcInfoS.l, ArcView3.1, MapInfoS.O software, basic data in the study area has been established, which including soil map, landuse map, contour map etc. And based on the database, the crop land class evaluation has been attained as follows: basic database establishmentthe design of database includes objectives, principle,demand, analysis conception and logical structure designs, data classification and data coding. It mainly include the foundation of TIN, and the item of the grade, slope and highness has been attained from it. Grade and coding of evaluate itemAccording to the impact of evaluate item to the arable land quality, which were graded. The grade index is different objectively, and grade index has great correlation with arable land quality, which is premise of Grade-Determination of Arable Land. Quantization of evaluate itemOn the base of the grade of evaluate items, which were endowed with number. deciding the impact of itemThere are many methods to decide the impact of item, for example expert analysis method, Fuzzy Integrated Method. This reseach adopt the layer analysis method to decide the impact of item. deciding the evaluate cellThe cell of 10 X 10 meter was conducted in this research, very vector map has been resampled to the same standard grid map. Different scale map can be used in this study, and the grid map can be exactly piled up. the choice of evaluate methodThe index accumulation method has conducted to evaluate land class, the integrated scores were counted and were decided the class of crop land. get the evaluate item's numberget the number of slope .aspect and elevation from tin; get number of soil type from soil map. result of grade-determination of arable landThe arable land , whose slope are less than 25 degree, are graded four grade According to the principle. The first grade arable land 725.41 hectares, the second grade arable land 1283.77 hectares, the third grade arable land 164.04 hectares, he forth grade arable land 34.17 hectares. The arable land whose slope exceed 25 degree would afforestated. compare the result of grade-determination of arable land with the result of basic farmland zonethe result of analyzeing: the basic farmland zone account for the first grade arable land 557.28 hectares, the second grade arable land 817.93 hectares, the third grade arable land 135.86 hectares, he forth grade arable land 31.32 hectares, the afforestated land 86.14 hectares. establishing on Basic farmlan...
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