Calculation of default sill, range and other parameters for the variogram model when Kriging or Cokriging in Surfer

When gridding data using kriging or cokriging in Surfer, the variogram defaults to a Linear component type with Slope equal to the data variance divided by the maximum Lag distance. The maximum Lag distance is defined by the Lag size multiplied by the Number of lags.

The Autofit tool assumes that the correct variogram model (Component type) has been chosen by the user. If the correct model is not applied, the Autofit tool may give unsatisfactory results. Autofit is only available for modelling kriging variograms, not for cokriging variograms or cross-variograms.

In Surfer 16 and previous:

The default parameters for Slope and Anisotropy are set to 1 with a Linear model in the Kriging Advanced Options dialog

• To model your data and get values for your dataset, click Grids | New Grid | Variogram | New Variogram, select your data file and click Open. Click OK in the New Variogram dialog to create the variogram.
  
  
• After the variogram is created, you can transfer the calculated parameters from the variogram to the kriging algorithm using the steps below.
  1. Click Grids | New Grid | Grid Data, selecting the data file and clicking Open.
  2. In the Grid Data dialog, select the Kriging gridding method.
  3. Click the Advanced Options button.
  4. In the Kriging Advanced Options dialog, click the Get Variogram button to transfer the calculated parameters from the variogram to the kriging algorithm.
  5. Click OK and OK to create the grid file.
     
     

For more information about variograms, please review this article. 

Updated October 2021