Lesson Note On Civil 3D Creating Contours From a Surface

Creating Contours From a Surface

To create contours from a surface

1. Build a surface. 

2. From the Terrain menu, choose Create Contours to display the Create Contours dialog box.

3. From the Surface list, select the surface that you want to create contours for. If the surface name is not displayed in the list, then click Browse to search for it. Surfaces have the file extension .tin.

4. Under Elevation Range, define the range of the surface's elevation for which to create contours by entering values in the From and To boxes. The low and high elevations of the surface are displayed as defaults.

TIP If you change the Elevation Range, then you can return to the default range by clicking the Reset Elevations button.

To exaggerate the elevational changes of the contours when you look at them in 3D, enter a value other than 1 in the Vertical Scale box.

NOTE If you exaggerate the vertical scale, the contours are drawn at an exaggerated elevation and are therefore incorrect when labeling or as a basis for future TIN creation.

5. Under Intervals, select one of the following options:

• Both Minor and Major
• Minor Only
• Major Only

6. Define the contour intervals by entering values in the Minor Interval and Major Interval boxes. For example, if you enter a minor interval of 2, and your drawing units are meters, then a minor contour is created every place there is a 2-meter change in elevation.

7. Specify the layers for the major and minor contours. By placing the minor and major contours on different layers, you can easily control the contour colors and linetypes. You can select a layer or type in a new layer name.

8. Under Properties, select one of the following options:

• Contour Objects: To create contour objects. 
• Polylines: To create polyline contours.

NOTE If you select the Polylines option, then you cannot select a contour style to use.

9. From the Contour Style list, select the contour style to use for the contours.

TIP Click the Preview button to see a preview of the contour style.

10. If you need to load a contour style, edit a style, or create a new style, then click the Style Manager button to display the Contour Style Manager dialog box.

11. Click OK to generate the contours.

The following prompt is displayed:

Erase old contours (Yes/No) <Yes>:

12. Type Yes or No:

• Type Yes to erase any existing contours that may be present on the contour layers.
• Type No to preserve existing contours.

WARNING! If you type Yes to erase the old contours, then existing contours on both the major and minor contour layers are erased. When you develop grading plans, pay attention to the layers that the Create Contours command uses so that your existing ground contours are not erased.