Choose whether to grid the original data or its logarithmic (base 10) form. Gridding in log space can help reduce distortion in highly skewed data, such as geochemical measurements.

Available options:

• linear: Grid the data as-is.
• log, save as linear: Grid the base-10 log of the data (in logarithmic space). Any values below Log minimum are clipped at that threshold. The resulting grid is converted back to linear space before being saved to a grid file.
• log-linear, save as linear:
• Values above the positive Log minimum and below the negative Log minimum are gridded in logarithmic space.
• Negative values are temporarily sign-flipped to compute logs, then flipped back.
• Values outside the ± Log minimum range are converted back to linear space post-gridding and scaled to ensure boundary continuity.
• Values within the ± Log minimum range remain intact and are gridded linearly.
• Finally, the linear representation of the data (in both ranges) is saved to the grid file.
• log, save as log: Same as log, save as linear, but grid values are kept in log space - the gridded data is saved to the grid file in its logarithmic representation.
• log-linear, save as log: Same as log-linear, save as linear, but the grid values are not converted back from log space. The output grid remains in logarithmic space with large amplitude anomalies being somewhat moderated.

Script Parameter: RANGRID.LOGOPT
  linear: 0
  log, save as linear: -1
  log-linear, save as linear: -2
  log, save as log: 1
  log-linear, save as log: 2

When gridding in logarithmic space (see Log option above), this parameter sets the minimum threshold value. The default is 1.

Script Parameter: RANGRID.LOGMIN

The de-sampling factor is defined as a function of the grid cell size. Before any further calculations, all points within cells of dimension cell_size x desampling_factor are averaged into a single value and placed in the center of the cell.

The default desampling (desampling_factor) is set relative to the contributing points as:

Desampling has two impacts:

• Effectively it acts as a low-pass filter. The larger this parameter the smoother the output grid.

• Speeds up the variogram calculation when the input database is very large.

If the database contains less than 100000 contributing points, the default is set to 1, and the only pre-filtering consists of de-aliasing at the cell level.

The variogram calculation duration is a function of the square of the contributing points. Increasing this factor visibly cuts down the variogram calculation time while little impact is seen on the variogram curve.

Script Parameter: RANGRID.DSF

All grid cells farther than the blanking distance from a valid point will be set to dummies in the output grid.
The default blanking distance is calculated as:

Preferably this parameter should be set to just greater than the maximum distance through which interpolation is desired.

Script Parameter: RANGRID.BKD

Specify the allowable absolute error per grid cell (in grid data units). The default is 0.1% of the observed data's maximum range.Lowering the tolerance increases grid accuracy.

Script Parameter: RANGRID.TOL

The minimum percentage of points that must meet the specified tolerance. The default is 99%. For a higher-quality grid, consider increasing this threshold.

Increase this percentage for a more accurate grid.

Script Parameter: RANGRID.PASTOL

Iterations at the finest coarseness level will stop when the maximum number or iterations is reached. At each greater coarseness, the maximum iterations is reduced by 2.Increase this value if more iterations are required to produce a more accurate grid.

Script Parameter: RANGRID.ITRMAX

Select a value of 16, 8, 4, 2, or 1 to set the desired coarseness of the starting iteration level relative to the final grid cell size. By starting with a coarser grid, the algorithm is able to produce a reasonable result in under-sampled areas. As the coarseness decreases, the algorithm becomes more sensitive to local features. Only reduce the starting coarseness from 16 if faster processing time is required.

Script Parameter: RANGRID.ICGR

Set the maximum search radius used to establish starting grid values for the coarse grid. Default: four times the coarse grid size set by the Starting coarse grid parameter. If no data is found within this radius, the mean of all data is used as the starting value. If the search radius is too small, the starting grid can be a poor approximation of the desired grid, resulting in excessive processing time. A radius that is too large may unnecessarily delay coarse grid generation.

Script Parameter: RANGRID.SRD

The degree of internal tension (between 0 and 1). Default: 0, resulting in a true minimum curvature grid with no tension.Increasing tension can be used to prevent overshooting of valid data in sparse areas; however, curvature in the vicinity of real data will increase. In general, the sparser the areas in the data—with localized highs and lows— the higher the tension should be set.

Script Parameter: RANGRID.IT

Edge clipping parameter, the number of grid cells to extend beyond the outside limits of the data. The default (-1) is not to apply edge clipping to the blanking distanced grid. Use this parameter to ensure the grid does not extend too far beyond the actual data limits, which can occur when using a large blanking distance with widely spaced data.

Script Parameter: RANGRID.EDGCLP

Weighting power is used to generate the coarse starting grid. Within each coarse cell, values are weighted by the inverse of their distance from the coarse grid nodes, raised to this power.The two weighting settings, weighting power and weighting slope, can be used to reduce high-frequency aliasing that may occur when gridding at overly coarse intervals.

Script Parameter: RANGRID.IWT

Weighting can be further refined using the slope parameter. The overall weighting is determined by the following expression:

Where:

• distance is in grid distance units.
• power is applied to the distance.
• slope is in cell units; the default is 0.0, meaning only the nearest data points influence the weight at each grid node.

Script Parameter: RANGRID.WTSLP