Select Samples

To access this screen:

Define the sample files and fields for estimation.

This screen is divided into two key areas:

  • Input Samples – Select the input sample file or, if you need to unfold data for estimation, an unfolding parameters file.

    By default, coordinate fields are auto-detected, but you can set them yourself if fields aren't recognized.

    Once an unfolding parameters or sample file is selected, choose one or more grade fields for the estimation.

    See UNFOLD in Advanced Estimation.

  • Input Zones – If zonal control is required, zones can be defined either using drillhole attributes or by specifying zone wireframes. In each case, up to 2 zones can be defined (Zone 1 and Zone 2). In either case, custom zones can be defined, although drillhole-based zoning will be performed using the "soft boundary" approach and, where wireframes are used, a distance-based "semi-soft boundary" technique is used.

    See Hard, Soft and Semi-Soft Boundary Estimation.

  • Sample Summary – Once you have defined your fields, a summary table displays with basic statistics such as the number of samples and distances between samples.

Sample Summary Statistics

When samples, at least one estimation variable and (optionally) zones are defined, the Sample Summary table shows summary statistics:

  • Zone – If one or two zones are specified, the statistics relating to either a zone, or a zone combination are listed on separate table rows. If two zone fields have been selected then the zone values will be separated by the “/” symbol. The bottom row is shown as zone “All”, giving statistics over all zones or in the case where no zones have been selected.

    Note: An All record always displays, showing summary information for the entire samples data.

  • Samples – The number of samples contributing to the estimation within the zone.
  • 2D – This shows "Yes" if , for each zone, the z-span of all the coordinates in the zone is close to zero. It shows "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, 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.

  • Absent lengths – The number of samples with an absent data FROM or TO value.

You can also Calculate distance statistics, which can take a few minutes to calculate for large data files (hence they aren't calculated by default):

  • 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.

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.

Select Samples for Estimation

The following activities assume the Advanced Estimation wizard is displayed, and that a scenario has been configured, and is active.

To specify input sample data for an estimation study (no unfolding):

  1. Browse for a Samples file. This will be a desurveyed drillholes or sample points file in either .dm or .dmx format.

    The grade/variable list below populates with the file's numeric fields, and if possible, the coordinate fields are selected below. A Hole ID field and FROM and TO fields are also automatically picked if they are recognized.

  2. Review the Select grade/variables fields list and check any grade or variable that will contribute to the estimation.
  3. Check that the X, Y and Z fields represent the coordinates of the samples. If not, select them.
  4. Decide whether zone control is performed, and if so, whether hard, soft, or semi-soft boundary estimation is used:
    • To perform estimation without zone control, leave both Input Zones as <none>. Estimation will only consider samples within the target domain when estimating.
    • To perform hard boundary estimation using the samples domain, ensure Wireframe Triangles is empty. Select a sample Zone 1 and (for multiple zones) Zone 2. In this scenario, no custom zones are defined.

    • To use custom zones for estimation, select the samples data domain (leaving Wireframe Triangles blank) for Zone 1 and (optionally) Zone 2. Custom zones are then defined on the Define Custom Zones screen. Including adjacent zones can result in soft boundary estimation.

    • To use soft or semi-soft boundary estimation, select a wireframe file or files for the input zone(s). The Tolerance distance for estimation is then above zero and defined using the Define Search Volumes screen. Setting a tolerance distance to equal or greater than the longest search range can result in soft boundary estimation.

      Note: Custom zones are not considered for semi-soft boundary estimation, even if defined.

    • To perform hard boundary estimation using one or two wireframes, select a wireframe file or files for the input zone(s). The wireframe files must define closed, non-overlapping zones and contain Zone 1 and, where applicable, Zone 2 values that match the prototype model. The Tolerance distance for estimation is then set to zero using the Define Search Volumes screen.

      Note: Custom zones are not considered for semi-soft boundary estimation, even if defined.

  5. Review and confirm the Hole ID, From and To fields. These denote independent holes and interval break points, so make sure they are set to the right fields.
  6. Review the Sample Summary statistics.
  7. Optionally, Calculate distance statistics.

To specify input sample data for an estimation study (with unfolding, hard boundaries):

  1. Check Use Unfolding.

  2. Browse for a Unfolding parameters file. This is typically output from the UNFOLD process but can also be exported from a previous session of the Advanced Estimation wizard.

    See UNFOLD in Advanced Estimation.

    The samples file, if it can be derived from the unfolding parameters file, is automatically set.

    The grade/variable list below populates with the file's numeric fields, and if possible, the unfolded coordinate fields are selected below. A Hole ID field and FROM and TO fields are also automatically picked if they are recognized.

  3. If you intend to adjust unfolding parameters, unfold data and save a parameters file, check Show Unfolding Parameters.

    1. Activate the Unfolding screen.

    2. Adjust or set unfolding parameters. See Unfolding.

    3. Click Run and Display.

    4. Activate the Parameters screen and check Export.

    5. Browse for a location and specify a name for your Unfolding parameters file.

    6. Return to the Select Samples screen and select the updated file.

  4. Review the Select grade/variables fields list and check any grade or variable that will contribute to the estimation.
  5. Check that the X, Y and Z fields represent the coordinates of the samples. If not, select them.
  6. Define your Input Zones either from drillhole or wireframe data.
  7. Review and confirm the Hole ID, From and To fields. These denote independent holes and interval break points, so make sure they are set to the right fields.
  8. Review the Sample Summary statistics.
  9. Optionally, Calculate distance statistics.

Related topics and activities