The Grids | Calculate | Isopach command can be used to generate an isopach or an isochore grid and map. Both maps show thickness between two surfaces. An isopach map is also referred to as True Stratigraphic Thickness (TST) map. This type of map represents the true thickness of a stratigraphic unit. An iso chore map, also known as True Vertical Thickness (TVT), shows the vertical thick ness of a unit. If the unit was horizontal, this would be the same as TST, but if units have a dip or incline, the vertical thickness is different from the strati graphic thickness.
Follow these steps to create an isopach or isochore map, for example to generate a contour map representing the thickness of a coal seam using drillhole data that provides the elevation of the upper surface and lower surface of the coal seam.
- Create grid files of the upper and lower surfaces (for example, grid files that define the elevation of the top and bottom of a coal seam). Both grids must use the same XY ranges and have the same number of rows and columns.
- Click the Grids | Calculate | Isopach command.
- In the Grid Isopach dialog, click the Browse button next to Upper Surface. In the Open Grid dialog, select the grid file for the upper surface and click Open or click the Download button to download a grid file.
- Click the Browse button next to Lower Surface. In the Open Grid dialog, select the grid file for the lower surface and click Open or click the Down load button to download a grid file.
- Based on the type of map that you want, click Isopach or Isochore from the Calculation Type section.
- Click the open folder button in the Output Grid section, enter the name for the thick ness grid file in the Save Grid As dialog, and click Save.
- Check the Add grid as layer to check box to display the grid or leave unchecked to just create the grid file listed in Output Grid.
- Select the layer type for the new grid from the New layer type list. 9. Click OK to generate the selected grid.
Created May 2021