Creating contour lines on a TIN

Contour lines represent constant elevation and show the topography of the landscape. More information on Contour Lines

• Select Home > Map > Add Theme.
• Select the overlay containing the TIN,.
• Select Annotation > Contour theme and click Next.
• In the Contour Styles dialog you can choose the spacing for the Major contours and Minor contours and the Pens to use for them.
   

Option	Description
Major contours Height	Draws major contour lines at each elevation that is a multiple of this height.
Pen	Pen to use for major contour lines.
Minor contours Height	Draws minor contour lines at each elevation that is a multiple of this height, unless the elevation is also a major contour.
Pen	Pen to use for minor contour lines.
Legend Annotation Units	Units to use in theme legend. (SIS Desktop 9 does not automatically place labels on the contour lines.)
Places	Decimal places to show in theme legend.
Show units	Check this tickbox if the units are to be shown in the theme legend.

Filter, Scale and Legend buttons

TIP: Click here for a description of these functions.

Creating smoother contour lines (Method 1)

There are two ways to create smoother contour lines; use Method 1 if there are not too many contours:

1. Use the Explode command to generate joined-up contour lines.
2. These are MultiLineString items, designated as a Static theme. You can use the Labels theme to label these contours if required.
   
3. Select the newly created MultiLineString items and use CAD > Alter > Smooth Vertex. This results in very smooth contours. But beware the contour lines may cross over each other and are not very accurate.
4. Before creating the contours, subdivide the TIN item (ideally more than once) using the TIN item command Subdivide (Edit > TINS). Related Topics

Example

This example illustrates Method 1 and uses Label settings for linear items controls in the Label Styles dialog.

1. Explode the contour theme.
   
   
2. Add a Label theme.
3. In the Label Styles, navigate to Label Placement inside the Advanced settings pane.
4. Choose Along from the drop-down box and set the Move to output drop-down box to True.
   
   
5. The result of exploding the theme are MultiLineStrings with originZ values, one MultiLineString for each contour value. Therefore there will now be very few labels shown on the screen.
   
6. Select Decompose.
7. Each contour line is now broken up into its component lines which were created from a TIN, this results in masses of LineString segments and masses of labels:
   
8. With the results still selected, choose CAD > Alter > Join LineStrings
9. Select the Exact radio button and enter 0 (zero).
   
10. Click Apply if you wish to see the effect in the preview pane:
    
11. Click OK.
12. The result will be as shown:
    

Method 2

Method 2 is theoretically more valid and usually makes more accurate contours which will not cross. However the resulting contours may not be as smooth as Method 1.

The following diagram shows a TIN with contours applied, then the same TIN subdivided twice before having contours applied.

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