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
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