Define Search Volume - Existing Estimations

To access this dialog:

Using the Advanced Estimation dialog, select the Define Search Volume menu item. The Estimation area is found on the left of the panel.

The summary information for each Estimation includes:

· Estimation number

· Summary description

· Grade

· Zone

· Search volume reference number

· Search volume dimensions

· Minimum number of samples

· Optimum number of samples per sector

If the estimation method is Inverse Distance or Nearest Neighbour, search parameters will not be defined automatically. In this case a new search volume can be created as described in the Available Search Volumes section below.

Create from variograms: if the default set of search volumes has been cleared (Clear list button at the bottom of the central area) then a new set can be generated using the Create search volumes from variograms button at the bottom of the left area.

Variance %: create a search parameter file at a given % of the total variogram variance by entering a value from >0 to 100 in this field. The total variance is calculated (NUGGET + sum of ST*N*PAR4 values, for N structures), then the distance at the specified % of that is determined. This length is determined through the range length of the spherical model.

This setting allows for the sizes of search parameters to be determined from variogram models, at ranges given a percentage of the total variance. These ranges are calculated directly from the variogram model, in the X, Y and Z directions. Each of these distances are used for the in the search parameters (SDIST1, SDIST2 and SDIST3), with the same rotation as the variogram model. This is for cases where you wish to limit the search neighbourhood based on the variogram ranges, but retain the anisotropy ratios determined in the variogram modelling.

A rule of thumb for interpolation is that samples selected for a robust neighbourhood might be found at ranges which are 70 % - 80 % of the total variance. This setting allows you to quickly identify distances at selected percentage variances and set those ranges to limit your primary search neighbourhood.

Where you see good continuity in your variogram, you might expect to find optimal ranges at lower percentage variance values (i.e. a smaller search neighbourhood would provide a robust estimate). In cases where you see a more nuggety variogram with poor continuity, you might expect to find optimal ranges at higher percentage variance values (i.e. a larger search neighbourhood would provide a more robust estimate, although your estimates will be more smoothed). The ellipsoid factors can be used to extend the secondary / tertiary searches by a ratio of the primary search neighbourhood.

The example below shows distances given variances of 75 % of the total variance (sill). In such an example we would samples for the primary search neighbourhood to fall within 19 m of the block being estimated, and thus would use those to limit the primary search at that distance:

Apply to estimations: if this box is ticked, search volumes will automatically be assigned to the Estimation from which the search volume has been derived.

	Related Topics
	Define Search Volume Define Search Volume - Available Define Search Volume - Parameters