3d Surface - External Data
This tab allows the user to select the interpolation scheme and the parameters of the interpolation method. The correct selection of interpolation parameters is critical for generation of contours that accurately reflect the field data and our expectations of how the values vary between the measured data points. The default parameters are frequently adequate, although some improvement can be anticipated through trial and error.
The kriging routines are derived from the kt3d routine of the Geostatistical Software Library (GSLIB) authored by Clayton Deutsch and Andre Journel (www.gslib.com).
The reference, GSLIB: Geostatistical Software Library and Users' Guide is highly recommended. Here are the spherical semivariogram models used by EnviroInsite for an isotropic system, where h is the lag, c is the sill, and a is the (practical) range. This is from this link to an introductory text on kriging: Click here for an introductory text on the variogram models
For anisotropic systems h/a in the previous is calculated as
Natural Neighbor Parameters
The natural neighbor interpolation makes use of an adapted version of the public domain nn code developed by Pavel Sakov of CSIRO Marine Research.