What is sample variogram?

Description. The function sample. variogram computes the sample (empirical) variogram of a spatial variable by the method-of-moment and three robust estimators. Both omnidirectional and direction-dependent variograms can be computed, the latter for observation locations in a three-dimensional domain.

What is a variogram used for?

A variogram is an effective tool for describing the behavior of non-stationary, spatial random processes. It is used primarily in spatial statistics, geostatistics, and statistical design; In geostatistics, it is an “essential step” for analyzing spatial variability (Gómez-Hernández et al., 1999).

What are variogram parameters?

Most variograms are defined through several parameters; namely, the nugget effect, sill, and range. These parameters are depicted on the generic variogram shown in figure 4.1 and are defined as follows: • nugget effect-represents micro-scale variation or measurement error.

What is a nugget in a variogram?

The nugget is the y-intercept of the variogram. In practical terms, the nugget represents the small-scale variability of the data. A portion of that short range variability can be the result of measurement error. The range is the distance after which the variogram levels off.

What is a variogram GIS?

The okapi (theoretical) variogram is a function describing the degree of spatial dependence of a spatial random field or stochastic process . It is defined as the expected squared increment of the values between locations and. (Wackernagel 2003): itself is called semivariogram.

What is variogram cloud?

Using all sample pairs in a data set (up to a distance of half the diameter of the region), a plot of the dissimilarities ,* against the spatial separation h is produced which is called the variogram cloud.

What is directional variogram?

A directional variogram is a variogram where point pairs are only included into the semivariance calculation if they fulfill a specified spatial relation. This relation is expressed as a search area that identifies all directional points for a given specific point.