Semivariance
Encyclopedia
In spatial statistics, the empirical semivariance is described by
where z is a datum
at a particular location, h is the distance between ordered data, and n(h) is the number of paired data at a distance of h. The semivariance is half the variance of the increments
, but the whole variance of z-values at given separation distance h (Bachmaier and Backes, 2008).
A plot of semivariances versus distances between ordered data in a graph is known as a semivariogram rather than a variogram
. Many authors call
a variogram, others use the terms variogram and semivariogram synonymously. However, Bachmaier and Backes (2008), who discussed this confusion, have shown that 
should be called a variogram, terms like semivariogram or semivariance should be avoided.
where z is a datum
Datum
A geodetic datum is a reference from which measurements are made. In surveying and geodesy, a datum is a set of reference points on the Earth's surface against which position measurements are made, and an associated model of the shape of the earth to define a geographic coordinate system...
at a particular location, h is the distance between ordered data, and n(h) is the number of paired data at a distance of h. The semivariance is half the variance of the increments
, but the whole variance of z-values at given separation distance h (Bachmaier and Backes, 2008).A plot of semivariances versus distances between ordered data in a graph is known as a semivariogram rather than a variogram
Variogram
In spatial statistics the theoretical variogram 2\gamma is a function describing the degree of spatial dependence of a spatial random field or stochastic process Z...
. Many authors call
a variogram, others use the terms variogram and semivariogram synonymously. However, Bachmaier and Backes (2008), who discussed this confusion, have shown that should be called a variogram, terms like semivariogram or semivariance should be avoided.See also
- VarianceVarianceIn probability theory and statistics, the variance is a measure of how far a set of numbers is spread out. It is one of several descriptors of a probability distribution, describing how far the numbers lie from the mean . In particular, the variance is one of the moments of a distribution...
- Sampling variogram
- GeostatisticsGeostatisticsGeostatistics is a branch of statistics focusing on spatial or spatiotemporal datasets. Developed originally to predict probability distributions of ore grades for mining operations, it is currently applied in diverse disciplines including petroleum geology, hydrogeology, hydrology, meteorology,...
- KrigingKrigingKriging is a group of geostatistical techniques to interpolate the value of a random field at an unobserved location from observations of its value at nearby locations....
- Post-Modern Portfolio TheoryPost-modern portfolio theoryPost-modern portfolio theory is an extension of the traditional modern portfolio theory...
External links
- Shine, J.A., Wakefield, G.I.: A comparison of supervised imagery classification using analyst-chosen and geostatistically-chosen training sets, 1999, http://www.geovista.psu.edu/sites/geocomp99/Gc99/044/gc_044.htm