基于空间自相关的耕地等别指数检验方法研究

Test Method of Cultivated Land Grading Index Based on Spatial Autocorrelation

耕地质量等别成果在我国耕地保护中发挥了重要作用,因此对耕地质量等别成果质量检验方法的研究具有重要的现实意义。建立了以耕地面积修正反距离权重矩阵的改进模型,并分别提取了改进模型和反距离模型的疑似异常值单元,得到了县域内所有耕地单元的自然等指数的标准差,选取大于增量空间自相关最大莫兰指数所对应的阈值距离为缓冲区半径,按照研究确定的县域耕地自然等指数疑似异常值判定与选取的标准,对疑似异常值单元与其缓冲区范围内耕地单元的自然等指数进行比较和判断,排除非确定异常值,得到确定异常值,并对最终结果进行了检验。以内蒙古自治区宁城县为例,分析得到自然等指数的标准差为78,缓冲区距离为600 m,结果表明,判定与选取异常值的标准能准确提取确定异常值单元,排除大部分非确定异常值,且检验表明,提取确定异常值的精度较高;在相同阈值距离下,改进模型比反距离权重模型在提取确定异常值单元方面存在一定优势,说明面积和距离都是影响耕地质量相关性的重要指标。该方法可以为县域耕地质量等别成果数据检验提供参考,也为空间自相关分析在相关领域中的应用提供一种新思路。

The cultivated land quality grading results have played an important role in the protection of cultivated land,therefore,research on the test method of cultivated land quality grading results has important practical significance. The main purpose of this study was to prove the rationality of the cultivated land quality gradating results by testing cultivated land natural quality index. This paper presented an improved model,and it was established with inverse distance weighting（ IDW） matrix which was amended by cultivated land area,then suspected outliers of the improved model and the original IDW model were extacted. In order to determine the accuracy of suspected outliers,a further study was carried out to establish a standard for judging and extracting suspected outliers,which included analyzing the standard deviation of cultivated land natural quality index of cultivated land unit,and selecting a distance which is greater than the threshold distance of biggest Moran index as a buffer radius.This new method was illustrated by using Ningcheng County of Inner Mongolia as a case study,the standard deviation was 78 and the buffer radius was 600 m were obtained. The results indicated that the method using standard to judge suspected outliers can accurately judge determined outliers and exclude most non-deterministic outliers. Besides,the improved model was better than the original IDW model on extracting the determined outliers unit in the same threshold distance,which illustrated that both the areaand the distance were important indicators of the quality of cultivated land. This method can provide a reference for testing the cultivated land quality gradating results at county level,and also provide a new way for the application of spatial autocorrelation analysis in related fields.