SAMPLE ADEQUATELY TO ESTIMATE VARIOGRAMS OF SOIL PROPERTIES
SAMPLE ADEQUATELY TO ESTIMATE VARIOGRAMS OF SOIL PROPERTIES
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DOI：
10.1111/j.1365-2389.1992.tb00128.x
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发表时间：
1992-03-01
期刊：
影响因子：
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通讯作者：
OLIVER, MA
中科院分区：
文献类型：
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作者：
WEBSTER, R;OLIVER, MA
变异函数是土壤空间分析的核心，但它往往是从少数数据估计，其精度是未知的，因为不能从一组数据分析确定的置信限。 土壤性质的变异函数的近似置信区间可以通过使用合理模型模拟一个大的值域，然后从中提取许多样本并计算每个样本的观测变异函数来数值计算。 然后，可以获得变差函数的抽样分布及其分布图。 在土壤和环境调查的典型情况下，根据少于50个数据计算的变异函数似乎没有什么价值，至少需要100个数据。 我们的实验表明，对于正态分布的各向同性变量，从150个数据的样本计算的变差函数可能往往是令人满意的，而来自225个数据的变差函数通常是可靠的。
The variogram is central in the spatial analysis of soil, yet it is often estimated from few data, and its precision is unknown because confidence limits cannot be determined analytically from a single set of data. Approximate confidence intervals for the variogram of a soil property can be found numerically by simulating a large field of values using a plausible model and then taking many samples from it and computing the observed variogram of each sample. A sampling distribution of the variogram and its percentiles can then be obtained. When this is done for situations typical in soil and environmental surveys it seems that variograms computed on fewer than 50 data are of little value and that at least 100 data are needed. Our experiments suggest that for a normally distributed isotropic variable a variogram computed from a sample of 150 data might often be satisfactory, while one derived from 225 data will usually be reliable.