| iTool User's Guide: Working with Surfaces |

## Contouring a Surface

Contour lines can be drawn directly on a surface to provide information about the levels of the surface, such as elevation. Two types of contours can be applied: multiple-level contour operations that apply to the surface in general, and single-level contour objects applied at a specific location on the surface.

To add contour lines to a surface:

1. Select the surface in the iTools window. For example, select the `isurfdemo.dat` surface data previously visualized.

2. Select Operations Contour.

3. The Contour dialog appears (shown below) allowing you to adjust contour setting, including:

- N_LEVELS: Set the number of contouring levels

- Value: Set the contour value to use

- Projection: Choose the contour type (Planar or 3D)

Figure 11-4: The Contour Dialog

Figure 11-4: The Contour Dialog

4. After making any contour property changes, select OK to contour your surface.

5. Contour lines are applied to the surface at the interval specified in the contour dialog.

Figure 11-5: Surface with Contours Added

Figure 11-5: Surface with Contours Added

6. To adjust the properties of the contour, double-click the contour in the iTool window or in the Visualization Browser to display the Contour property sheet. For information on the contour properties, see Contour.

To insert a contour object at a specific location on a surface:

1. Select a surface in the iSurface window.

2. Click the Surface Contour button in the Manipulator toolbar.

3. Click the level on the surface at which you would like the contour to appear. Contour lines are displayed on the surface at that level.

4. To adjust the properties of the contour object, double-click the contour object in the iTool window or in the Visualization Browser to display the Contour property sheet. For information on the contour properties, see Contour.

IDL Online Help (March 01, 2006)