3d Contours - External Data
This contour-points routine generates 3d contours or 2d-profile contours from point data stored in text files. Each record has the x-y-z coordinates and a data value. The values can be comma-delimited or space delimited. The contouring control options are the same as the 3d contour routine options used in contouring measured data from the EnviroInsite database.
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