Stratified mode

Stratified kriging or simulation (each variable with it's direct variogram applies to a specific area in the mask map) is the default action if the following conditions hold (example 12):

• more than one data variable is defined
• only for the first data variable output maps (predictions, variances) are defined
• the (first) mask map defined has more than one category

Data variables are numbered in the order they appear in the command file, starting at 0. Let the minimum grid value of the (first) mask map be $m$, If at a specific grid cell the mask map has value $j$, then for that cell the stratified prediction map (and variance map) will have predictions for variable $j - m$ (rounded to the nearest integer). Thus, predictions at mask map cells having value $m$ will get predictions for the first variable.

In case of universal kriging or least squares prediction with user-defined base functions, the maps with base function values should follow the category map: in the stratified mode the first mask map is the map with the categories.