3. Integrated analysis of spatial and attribute data - RTC, Regional ...

Understanding a semivariogram—the range, sill, and nugget‣ Sample locations separated by distances closer than the range are spatiallyautocorrelated, whereas locations farther apart than the range are not.‣range= The distance where the model first flattens out‣sill = The value that the semivariogram model attains at the range (the valueon the y-axis).Theoretically, at zero separation distance (i.e., lag = 0), the semivariogram valueshould be zero.However, at an infinitesimally small separation distance, the difference betweenmeasurements often does not tend to zero.This is called the nugget effect.For example, if the semivariogram model intercepts the yaxis at 1.34, then 95thenugget is 1.34.