Creating an Indicator Interpolant

An indicator interpolant is a useful way of creating a region of interest in which further processing can be carried out. For example, you can use an indicator interpolant to define a volume that encloses the values that are likely to be above a cut-off threshold and then carry out further interpolation inside that volume.

This topic describes how to create and edit an indicator interpolant. It is divided into:

Creating an Indicator Interpolant

To create an indicator interpolant, right-click on the Interpolants folder and select New Indicator Interpolant. The New Indicator Interpolant window will be displayed:

This window is divided into four parts, which determine the values used to create the interpolant, the interpolant boundary, any compositing options and general interpolant properties.

If you are unsure of some settings, most can be changed later. However, the Numeric values object selected when the interpolant is created cannot be changed.

Selecting the Values Used

In the Values To Interpolate part of the New Indicator Interpolant window, you can select the values that will be used and choose whether or not to filter the data and use a subset of those values in the interpolant.

You can build an interpolant from either:

  • Numeric data contained in imported drillhole data.
  • Points data imported into the Points folder.

All suitable data in the project is available from the Numeric values dropdown list.

Setting the Cut-off

The Cut-off value will be used to create two output volumes:

  • An Inside volume that encloses all values likely to be above or equal to the Cut-off value.
  • An Outside volume that enclose all values likely to be below the Cut-off value.

If you are unsure of what Cut-off value to use, you can view statistics on the distribution of the data and change the Cut-off value once the interpolant has been created.

You can change the names of the Inside and Outside volumes once the interpolant has been created.

Applying a Query Filter

If you have defined a query filter and wish to use it to create the interpolant, select the filter from the Query filter list. Once the model has been created, you can remove the filter or select a different filter.

Applying a Surface Filter

All available data can be used to generate the interpolant or the data can be filtered so that only the data that is within the interpolant boundary or another boundary in the project influences the interpolant. The Surface Filter option is enabled by default, but if you wish to use all data in the project, untick the box for Surface Filter. Otherwise, you can select the Interpolant Boundary or another boundary in the project.

You can use both the Query Filter option and the Surface Filter option together.

The Interpolant Boundary

There are several ways to set the Interpolant Boundary:

  • Enter values to set a Custom boundary.
  • Use the controls in the scene to set the Custom boundary dimensions.
  • Select another object in the project from the Enclose Object list, which could be the numeric values object being interpolated. The extents for that object will be used as the basis for the Custom boundary dimensions.
  • Select another object in the project to use as the Interpolant Boundary. Click the Existing model boundary or volume option and select the required object from the dropdown list.

Once the interpolant has been created, you can further modify its boundary. See Adjusting the Interpolant Boundary.

Compositing Options

When numeric values from drillhole data are used to create an interpolant, there are two approaches to compositing that data:

  • Composite the drillhole data, then use the composited values to create an interpolant. If you select composited values to create an interpolant, compositing options will be disabled.
  • Use uncomposited drillhole data to create an interpolant, then apply compositing settings to the interpolated values. If you are interpolating uncomposited values and do not have specific Compositing values in mind, you may wish to leave this option blank as it can be changed once the model has been created.

If you are interpolating points, compositing options will be disabled.

See Numeric Composites for more information on the effects of the Compositing Length and Minimum Coverage settings.

General Interpolant Properties

Set the Surface resolution for the interpolant and whether or not the resolution is adaptive. See Surface Resolution in Leapfrog Geo for more information on the effects of these settings. The resolution can be changed once the interpolant has been created, so setting a value in the New Interpolant window is not vital. A lower value will produce more detail, but calculations will take longer.

An indicator interpolant produces a single isosurface that is used to determine the likelihood of values falling inside or outside of the cut-off threshold. The Iso value can be set to values from 0.1 to 0.9. Clicking the arrows changes the Iso value in steps of 0.1. To use a different value, enter it from the keyboard. Again, this option can be changed once the interpolant has been created.

Enter a Name for the new model and click OK.

The Indicator Interpolant in the Project Tree

The new interpolant will be created and added to the Interpolants folder. The new interpolant contains other objects that represent different parts of the interpolant:

  • The Boundary object defines the limits of the interpolant. See Adjusting the Interpolant Boundary.
  • The Trend object describes the trend applied in the interpolant. See Changing the Trend for an Indicator Interpolant.
  • The points data values object contains all the data used in generating the interpolant. See Adjusting the Values Used.
  • The isosurface is set to the specified Iso value.
  • The Indicator Volumes legend defines the colours used to display the volumes.
  • The Output Volumes folder contains the Inside and Outside volumes.

Other objects may appear in the project tree under the interpolant as you make changes to it. See Editing an Indicator Interpolant for more information on the changes you can make.

Indicator Interpolant Display

Display the interpolant by:

  • Dragging the interpolant into the scene or right-clicking on the interpolant and selecting View Output Volumes. Both actions display the parent interpolant’s output volumes.
  • Right-clicking on the interpolant and selecting View Isosurfaces.

You can also display the values () used to create the interpolant, which is useful in making decisions about the Cut-off value and the Iso value:

Indicator Interpolant Statistics

You can view the statistics for the indicator interpolant by right-clicking on the interpolant and selecting Statistics. Use the information available to adjust the cut-off value and other interpolant properties:

You can copy the information displayed in the Statistics tab to the clipboard for use in other applications.

Once you have created an interpolant, you can adjust its properties by double-clicking on it. You can also double-click on the individual objects that make up the interpolant. See Editing a Numeric Interpolant for more information.

See also: