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3D Interpolation


The Scene Viewer is able to display and animate 3D volumetric plumes of one or more soil or groundwater contaminants. The plume is generated using the 3D Interpolation tool, then displayed with the Scene Viewer. The following section describes how to interpolate 3D points data in order to create 3D plumes; for details on viewing the plume, see the Scene Viewer section.

The 3D Interpolation starts with a data set - the data set must be created by building, executing, and saving a query with the Query Builder. The query must contain the data set your are interested in analyzing, along with the fields containing the data required by the 3D Interpolation, which include the following:



Z (elevation of sampling point)

Value (concentration value for one or more constituents)

Sample Date (if transient plume display is desired)


The Z value should be a field that represents the depth or elevation at which the data value (sample) was observed. If you want to display the plume on the same elevation scale as your cross sections (where data are displayed as an elevation) you may need to convert your sample depths to sample elevations. This can be done in the query builder, by adding a calculated display field, as shown below:


The last display field in the screenshot above, combines the sample elevation, and the screen depth (from) fields; the screen depth is subtracted from the station elevation (or station TOC elevation if desired), using the Expression below:

Expression: station.elevation - soil_sample.end_depth

Alias:        Z


Executing this query, will produce the results shown below:


The last column displays the calculated sample elevations (Z). This value should be mapped to Z in the 3D Interpolation to generate your plume.


Please Note: It is recommended that the X, Y, and Z fields all be displayed with the same length units.


Once you have created a data query, you may use the 3D Interpolation module to generate a plume. To access the 3D Interpolation tools, select Tools / 3D Interpolation from the main menu, and the following dialog will appear:


In the 3D Interpolation window, specify the various settings related to the grid size, extents, and data mappings.


3D Plume Project Name: Define the plume project name. One plume project can contain multiple plumes (e.g. for one or more contaminants).


Data Source

Define the various properties relating to the data source:

Data Source: select a field from the data query that contains the data to be interpolated (e.g. concentration, or result value)

Name: define a name for the parameter

Date Field: select the field that contains the sampling date (if available)

Date Granularity: This option controls how to accumulate the data items of various date stamps. For example, assume you have data for the following sample dates (could be from the same, or other stations):


5 stations sampled on 03/05/99

6 stations sampled on 03/14/99

4 stations sampled on 03/19/99

5 stations sampled on 03/27/99

6 stations sampled on 04/04/99

5 stations sampled on 04/15/99

4 stations sampled on 04/25/99


If you select Day for date granularity, you will obtain 7 data sets to interpolate.


If you select Month for date granularity, you will obtain 2 data sets to interpolate:

20 stations sampled in March, and

15 stations sampled in April


If you select Year for date granularity, you will obtain only one data set, which will effectively result in a static plume for this dataset.

In each case (day/month/year), the first observation from a given location (station) will be included in the interpolation.


Grid Region

Define the various properties relating to the grid size:

X Value: select a field from your query to be used for the X axis

# of nodes: define the number of grid nodes in the X direction

X min, X max: define the minimum and maximum X values for the interpolated grid; by default, these will be read from the data source, however you may modify these values if necessary

Similar parameters exist in the Y and Z directions.


Interpolation Method:

Available interpolation methods include:

Krigging (default), and

Inverse distance


Advanced Settings

Press this button to see advanced settings for the selected interpolation method:

Advanced Settings for Kriging

Advanced Settings for Inverse Distance Settings Inverse Distance


Interpolate log values

This option will interpolate the log values of the data points and then invert the log value distribution. This option is useful when interpolating data with a high degree of variance.


When you are finished, click on the [OK] button.

HGA will create a 3D plume file, in the "Plumes" sub-directory for your project, with the file name provided, and the extension .nc. For example,, in the directory:

 D:\Program Files\HGAnalyst\Projects\Demo_Project\Plumes


To display the plume, proceed to the instructions in Scene Viewer.

In addition to the *.nc file, HGA will save a *.txt file that stores the results from the query (x, y, z, value) that is used by the interpolator in generating the interpolation using the same file name, and in the same "Plume" sub-directory.


Please Note: Currently there is no method of opening plume projects in the Interpolation tool to make modifications. Therefore, it is suggested that you save the data query so the 3D Interpolation can be quickly re-created if necessary.



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