Geophysical Data

The types of geophysical points and grids that can be imported into Leapfrog Geo are:

• 2D Grids
• ASEG_DFN Files
• UBC Grids
• GOCAD Models

2D Grids

Leapfrog Geo imports the following 2D grid formats:

• Arc/Info ASCII Grid (*.asc, *.txt)
• Arco/Info Binary Grid (*.adf)
• Digital Elevation Model (*.dem)
• Intergraph ERDAS ER Mapper 2D Grid (*.ers)
• ESRI .hdr Labelled Image (*.img, *.bil)
• SRTM .hgt (*.hgt)
• Surfer ASCII or Binary Grid (*.grd)
• Grid eXchange File (*.gxf)
• Geosoft Grid (*.grd)

To import a 2D grid, right-click on either the Geophysical Data folder and select Import 2D Grid. Navigate to the folder that contains grid and select the file. Click Open to begin importing the data.

The Import 2D Grid window will appear, displaying the grid and each of the bands available. Select the data type for each band and set the georeference information, if necessary. See Importing a Map or Image for information on georeferencing imported files.

Once the grid has been imported, you can set its elevation, which is described in Setting Elevation for GIS Objects and Images.

When you display the grid in the scene, select the imported bands from the shape list:

Grids can be displayed as points () or as cells and the values filtered, as described in Displaying Points.

ASEG_DFN Files

Leapfrog Geo imports ASEG_DFN points in *.dfn format. To import an ASEG_DFN file, right-click on the Geophysical Data folder and select Import ASEG_DFN. Leapfrog Geo will ask you to specify the file location. Click Open to import the file. In the window that appears, enter a name for the file, then click OK. Next set the X, Y and Z coordinates and click OK. If you select no column for the Z coordinates, all Z values will be set to zero.

The file will appear in the Geophysical Data folder.

UBC Grids

Leapfrog Geo imports UBC grids in *.msh format, together with numeric values in properties files in *.gra, *.sus, *.mag and *.den formats. UBC grids can be evaluated against geological and numeric models, which can then be exported with the grid.

Importing a UBC Grid

To import a UBC grid, right-click on the Geophysical Data folder and select Import UBC Model. In the window that appears, click Browse to locate the file to be imported. Click Add to add any properties file, although these are not required.

For any properties file, click the Inactive Value field to mark cells as inactive. Doing so does not change the data but ensures that cells with the inactive value can be hidden when the grid is displayed in the scene. If you do not set this value when importing the grid, you can set it later by double-clicking on the grid in the project tree.

Click Import. The grid will appear in the Geophysical Data folder.

Evaluating UBC Grids

UBC grids can be evaluated against geological and numeric models as described in Evaluations. However, UBC grids cannot be evaluated against fault blocks and mutli-domained RBF interpolants, although they can be evaluated against the parent geological model and the parent numeric model.

Mapping Category Evaluations

When a UBC grid is exported with a category evaluation, category data is mapped to an editable numeric value. You can edit this by double-clicking on the grid in the project tree, then clicking on the Export Mappings tab:

Change the numeric value assigned to each lithology, if required. You can also change the value assigned to blocks that have no lithology.

Exporting a UBC Grid

To export a UBC grid, right-click on it in the project tree and select Export. Select the evaluations to export with the grid, then select a folder. Click OK to export the grid.

A UBC grid can also be exported as points to a CSV file. To do this, right-click on the grid and select Export as Points. You will then be prompted to select a file name and location. Once you have clicked Save, select the CSV export options for null values and numeric precision, then click OK.

The CSV file will contain:

• X, Y and Z columns, which represent the centre of each grid block
• I, J and K columns, which is the grid block index. I is in the range 1 to NI, J is in the range 1 to NJ and K is in the range 1 to NK, where NI, NJ and NK are the grid dimensions.
• One or more data columns

GOCAD Models

To import a GOCAD model, right-click on the Geophysical Data folder and select Import GOCAD Model. Leapfrog Geo will ask you to specify the file location. Click Open to import the file.

In the window that appears, set the Subsample Rate and enter a Name for the model. Click OK to import the model, which will appear under the Geophysical Data folder.

You can then evaluate geological models, interpolants and distance functions in the project on the model. In the case of geological models, you can also combine two or more models to evaluate on the model. To evaluate a model, right-click on the model object in the project tree and select Evaluations. See Evaluations for more information.

A GOCAD model can be exported as points to a CSV file. To do this, right-click on the grid and select Export as Points. You will then be prompted to select a file name and location. Once you have clicked Save, select the CSV export options for null values and numeric precision, then click OK.

The CSV file will contain:

• X, Y and Z columns, which represent the centre of each grid block
• I, J and K columns, which is the grid block index. I is in the range 1 to NI, J is in the range 1 to NJ and K is in the range 1 to NK, where NI, NJ and NK are the grid dimensions.
• One or more data columns

 

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