Define Custom Zones

To access this screen:

Using the Advanced Estimation wizard, select Define Custom Zones from the left-hand menu system.

Note: This panel requires that at least one zone has been defined for your estimation scenario.

This panel is used to define custom zones based on the unique attribute values (or combinations of values) found in the selected Zone 1 and Zone 2 fields on the Select Samples screen. Values on this screen are derived from the input samples.

You can select any of the sample zones listed on the left and combine them into a single Custom zone. This is useful when you want to review or report on broader groupings of zones without changing the source coding of the samples.

Note: Custom zones remain available for review and summary statistics, but semi-soft boundary estimation is configured using the wireframe and search-volume settings elsewhere in the workflow rather than from this panel. See Select Samples.

For example, if both Zone 1 and Zone 2 attributes were chosen, where Zone 1 contains values 1, 2 and 3 and Zone 2 contains values A and B, the following combinations are generated:

1/A, 2/A, 3/A, 1/B, 2/B, 3/B

You can then assign any of these combinations to a custom zone. For example, 1/A and 2/B.

If only one zone field is specified on the Select Samples panel, the unique values of that zone (including absent, if absent zone values exist) are listed.

Once a custom zone has been defined, the Bivariate Statistics screen can be used to generate zone statistics.

Zone Information in Output Files

If zone control is required and you choose to output a SAMPOUT file (containing information about which samples contribute to a block estimation), the following fields in that file can help you understand more about how zonal control has been applied to the estimation. The following fields are included in the SAMPOUT file for this purpose:

I_{Zone}	The {Zone} from which the sample originates (the input zone).
O_{Zone}	The {Zone} that the sample effects (the output zone).
O_IJK	the IJK value of the block model.

Similarly, the output model will contain a COUNTFLD field, the value of which will be defined by the Zone Parameter (ZPAR) file, where used. There will be one column for each zone combination configured in the model and, if set up using the Advanced Estimation wizard, will be set in the format {Zone1}/{Zone2}_N.

Custom Zone Sample Summary

The summary table displays the following columns:

Custom Zone Sample Summary – This command group contains a table showing, for each distinct zone.
Zone – Custom zone identifier(s) for each combination of zone values. If two zone fields have been selected then the zone values will be separated by the “/” symbol. The bottom row will be shown as zone “All”, giving statistics over all zones or in the case where no zones have been selected.
Samples – The total number of samples for the specified zone(s).
2D – Will state "Yes" if , for each zone, the z-span of all the coordinates in the zone is close to zero. It will show "No" if this isn't the case, and the data will be treated as 3D.
No of Holes – If a Hole ID field has been selected above, this column contains the number of holes for which zone values have been detected.
Range dist – The span of the data hull enclosing all samples. This distance is normally greater than the maximum distance between any samples (unless the hull has a sample exactly at the opposing corners).
Mean length: – The average sample length, calculated as TO - FROM
Absent lengths: – The number of samples with an absent data FROM or TO value.
Calculate distance statistics – Statistics are normally calculated when a new Samples file is specified, but you can use this button to calculate the following additional statistics for the samples file:
- Max dist – The maximum distance between samples, per zone (if one or more zones is specified).
- Mean dist – The average distance between samples, optionally per-zone.
- Min dist – The closest distance between sample pairs, optionally per-zone.

SAMPOUT File Data

If you choose to output a SAMPOUT file (classifying samples relative to the domain) the fields I_Domain and O_Domain are generated:

I_Domain references samples inside the domain and considered during estimation.
O_Domain references samples that are within a tolerance distance outside of the domain, and not considered during domain estimation.

See Run Estimations.

Hard, Soft and Semi-Soft Boundary Estimation

In many estimation studies there will be a 1:1 match between the zone in which the model cell is located and the zone in which the samples are located. In this scenario, only samples in zone N are used to estimate model cells in zone N. These zone boundaries are defined as Hard boundaries.

If the geostatistical characteristics of two or more zones are similar it may be beneficial for estimation to include samples from other zones. This is particularly useful if some zones have few samples. Defining soft boundaries allows zones to be defined according to input sample attribute values, and the estimation to use samples from more than one zone. For example, samples in zones 2, 4 and 6 are used for estimating model cells in zone 2; samples in zones 4 and 6 for cells in zone 4, and samples in zones 2 and 6 for cells in zone 6. In this situation the zone boundaries are defined as Soft boundaries.

Another option is to use soft boundaries, but constrain the extent to which neighbouring zone samples are considered for estimation by the specification of one or two wireframe volumes within a tolerance distance. These act as limiting boundaries, ensuring only samples within the wireframe shape (or shapes) contribute to cell estimation. This constricted form of soft boundary estimation is known as semi-soft boundaries. In this scenario, samples outside a domain can still influence estimates inside the domain, but influence is limited to a defined distance from the boundary, where the distance is defined as a tolerance using the Define Search Volumes screen. The semi-soft approach can result in a more controlled transition between domains.

Important: Input wireframes for semi-soft boundary estimation require a domain field, and the domain code must match the block model.

Note: If you are using two wireframes for two zones, they must not overlap.

Optionally, soft boundaries can be modelled by defining Custom zones of two or more sample zones. Each custom zone is then assigned to a model zone when the estimations are defined using the Define Estimations screen.

Alternatively, you can use the hard boundaries approach by not defining custom zones.

Create Custom Zones

To define or edit custom zones for estimation:

Display the Advanced Estimation wizard.
Select input samples and, if required zone data on the Select Samples screen.
Display the Define Custom Zones screen.
Select one or more of the sample zones listed on the left (Select zones). These are the zones that will be considered when assessing sample values as part of estimation.
Click Add Zoneto create a Custom zone representing the currently selected zones on the left. The Custom zone name is a concatenated string of all selected zones.

Tip: You can call a Custom zone anything you want by selecting it and clicking Rename.
Select a custom zone to update the list on the left to show which sample zones make up that custom zone (highlighted by a selected check box). You can change custom zone assignments by editing the check boxes on the left and clicking Update.

Note: If there is a Custom zone you no longer need, you can Delete it. If this custom zone is already being used elsewhere in the current scenario, deleting it may require you to review estimation settings before running the estimate.

Note: You can remove all custom zones using Clear list. This cannot be undone.
The Custom Zone Sample Summary table at the bottom of the panel displays statistics of all defined custom zones. See "Custom Zone Sample Summary", above.
To assess custom zones further, you can generate statistics for them using the Bivariate Statistics screen, where they are listed alongside standard zones (or zone combinations).