How to Create Gridded surface using Encom Discover 9.0

This tutorial shows how gridded surfaces and contour plans are created and used in Discover. A topographic dataset containing spot heights is used as the data source.
An Exercise in Surface Modelling and Analysis Elevation data, stored as a series of spot height points, are located in the table called SPOT HEIGHTS in the \Discover Tutorial \Surfaces folder. The objectives of this tutorial are to interpolate a surface grid and generate a contour plan, create a profile, determine grid slope and aspect, perform sun-shading and clip the grid to a region.

 Step 1 – Configure Grid Handlers
Discover can create surface grids in 3 widely used grid formats: Geosoft *GRD, ER Mapper *.ERS and Surfer *.GRD. Apart from creating grids in these formats, Discover can also import grids created in other gridding software applications including the following:
•Geosoft
•ER Mapper
•Surfer
•Vertical Mapper
•ESRI ASCII
•Other ASCII grids
•USGSDEM
•Minex
•BIL
Discover supplies a number of Grid Handler files which enable it to create or import grids in any of these formats.
Select Discover>Configuration>Grid Handlers and make sure that the following grid handlers are listed. Check the Use MapInfo Grid Handlers (when possible) box and highlight either the ERMapper, Geosoft or Surfer grid to be the default output grid type. The default output grid type can be overwritten when a new grid is created. Click OK.

Step 2 – Generate a Surface Grid
Open the table SPOT HEIGHTS. Choose Map>View Entire Layer. From the Discover menu, select Surfaces menu. The Surfaces menu is added to the MapInfo menu bar.
Choose Surfaces>Create Grid…. Select the SPOT HEIGHTS table to be gridded and click OK. Note that if only a portion or subset of the displayed data points is to be gridded, an additional Selection option appears in the dialog list.

The Gridding Tool consists of a series of tab dialogs for grid parameter set-up that create a surface grid. Accompanying each dialog box is a preview window of the grid as it is created.
The Gridding Tool consists of a series of tab dialogs for grid parameter set-up that create a surface grid. Accompanying each dialog box is a preview window of the grid as it is created.

On the Input tab of the Gridding dialog, select Elevation from the list of available fields to grid. The image appears on the right hand side of the dialog. Above the grid preview are 6 buttons and a pull-down list. These buttons control the display properties of the grid in the Preview window. Ensure that the Apply histogram equalisation button is selected and select pseudocolor from the drop down list of colour tables.
Right-mouse click in the Preview window to display the pop-up menu:



On the Method tab, set the Method to Triangulation. The gridding methods provided use different algorithms in order to interpolate values for grid cells from and between the input data points. Triangulation uses the Delaunay triangulation method which creates triangles between all the data points. Grid cell values are then assigned based on the coplanar values of the triangle in which each grid cell is located. This gridding method is best suited to datasets which need to honour the original data input points as accurately as possible: e.g. elevation data.
Other types of datasets such as geochemical data can be gridded using different interpolation methods such as Minimum Curvature or Inverse Distance Weighting.
The Grid Geometry tab specifies the grid cell size which may be altered manually if required. The extents of the data to be gridded can also be altered under the Data Coverage options.
On the Output tab save the grid in a Geosoft format [.GRD] named TOPO_GRID.TAB. Click the OK button and Discover will save the grid and open it up into a new map window or the map window containing the SPOT HEIGHTS data.
Step 3 – Contour Elevation Grid
Select Surfaces>Contour a Grid and the Contour a Grid dialog appears. Choose TOPO_GRID as the Grid to contour, check the Contour Smoothing box and the Specify minimum/maximum values to contour between box, leaving the range as 0 and 1200. Click on Output Contour Table and save the table as GRID_CONTOURS in the Discover Tutorial\Surfaces folder.

Click OK and Discover adds the new contour table to the TOPO_GRID grid map window. You can use the Surfaces>Label Contour Lines menu option to add contour labels to your contours.
Close the GRID CONTOURS table on completion of this exercise.