Smooth Contours

Smooth out and filter contour lines with tightly curved or angular line segments.

Smoothing is performed using the bSpline algorithm. When using this option, the distance between vertices is shortened by adding additional vertices. By having shorter edges, smoother curves are achieved.

Filtering is based on the Douglas-Peucker algorithm. When using this option, vertices are removed from the lines if they are not necessary.

Interface

The Smooth Contours dialog box contains smoothing and filtering options.

Procedure

1. Select a layer containing contours.

2. Select a contour line.

3. Select the Contour Smoothing command.

4. Click the check box for the Smooth option if you want to smooth the lines.

• If you select the Smooth option, enter the degree of smoothing you wish to apply in the bSpline Order field, with 10 being the largest possible value.

5. Click the check box for the Filter option if you want to remove unnecessary vertices.

If you select the Filter option, you must specify a tolerance to use for the filtering. You can choose to filter by millimetres (mm) at map scale, which requires you to enter a scale, or by metres on the ground.

6. Select the Tolerance Value to apply.

If you chose mm at map scale, enter a value in the map scale field.

7. Enter the number of units by which to perform filtering in the Dopu Filtering Tolerance field.

8. Click OK.