Smoothing Contour lines

An contour lines map generated using traditional analogic methods produce contour lines with the property of being visually smooth. When contour lines are generated from digital systems using regular rectangular grids or triangular irregular networks, sharp borders are observed. A smoothing contour lines method creates a curve approximation for this data.
A Catmull-Rom Spline was selected to smooth the contour lines because of its interpolation properties for the control points and its computation simplicity.

The figure below shows the contour lines smoothed in dotted lines and the original as continuous lines.

 
Smoothing Contour lines:

  • activate, in the "Control Panel", the Information Layer that has the data (samples or contour lines) to be smoothed;
  • click on DTM - Line Smoothing... in the main menu;
  • in Input: click on the representation that will be smoothed: Sample or Contour Line The system enables only the existing representation(s) associated to the active input IL;
  • type the Output Infolayer's name that will have the simplified lines. By default the system presents the name of the active IL. If the user wants to preserve the original data, type another name for the output IL;
  • type the Simplification Factor. This value will be used to filter the input lines. By default the system presents a value computed from the scale defined for the active IL (0.4 mm in the scale). This value can be modified;
  • type the Maximum Distance. This value defines the distance among the simplified lines. By default the system presents a value computed from the scale defined for the active IL (0.4 mm in the scale). This value can be modified;
  • click on Apply to smooth the lines.

NOTE: Output Simplify button: when selecting this button the lines, after smoothing, will be simplified using the Douglas-Peucker method, using as simplification tolerance the same factor used for smoothing.

See also:
DTM Products in the SPRING - What are they and How to execute them?
Numerical Maps Editing