农用地级别划分的常用方法比较

研究目的:对定级指数确定后的农用地级别划分的常用方法进行比较分析,为农用地定级工作的开展提供借鉴。研究方法:统计分析法,实证研究法。研究结果:(1)数轴法仅适用于定级单元数较少时的级别划分;(2)定级指数频率曲线法所分级别,随着组数n逐渐增大而增加,到一定程度后可分级别将保持不变;(3)定级指数频率曲线法和等间距法划分级别存在的差异仅限于一个级别;(4)定级指数频率曲线法对于定级指数区间中值附近的单元,划分的土地级别较为准确;(5)采用等间距法,级别内单元数量较为平均,可划分的级别数量决定于组距;(6)等间距法对分布于定级指数较高或者较低的定级单元划分的级别较为准确。研究结论:3种常用的级别划分方法适用的条件和参数选择均不同,应根据定级指数的具体情况,选择合适的级别划分方法。

Comparison on the Popular Methods of Agricultural Land Gradation

The purpose of this paper is to compare the popular methods of agricultural land gradation in order to provide theoretical references for the agricultural gradation projects in China. Methods employed include statistic analysis and empirical research. The results indicate:（1）the so-called Number Axis method is applicable when the gradation units are not many;（2）the gradation categories obtained through the method of so-called Gradation Index Frequency Curve will increase along with the enlargement of the assessed units, however after reach a certain degree the gradation categories will remain unchanged;（3）the difference between results obtained through the method of Grading Index Frequency curve and the method of so-called Equal Space is not obvious; in fact it shows only one grade difference;（4）regarding to the units near the mean value of gradation indices, the results are more accurate via the method of Gradation Index Frequency Curve than other methods;（5）the unit numbers within each grade category are averagely distributed when the method of equal space is used, and the total number of grade categories depends on group spaces;（6）when the method of Equal Space is used, the gradation results located in high or low gradation categories are more accurate those located in other categories. It is concluded that the compatibility of the three popular methods for gradation are different in terms of purpose and parameter selections. Therefore it is necessary to choose appropriate grading methods in accordance with practical conditions.