Smooth
Isolines
A
generated isoline map in traditional analogical methods produces
isolines with visual smooth properties. When isolines are obtained in
digital systems from regular rectangle grid or irregular triangle grid,
it is observed sharp corners. A smooth isoline method creates
curve format to that data.
Catmull-Rom
Spline was selected to smooth isolines due to its control
point interpolation properties and calculation simplicity.
Isolines before smoothing:

Isolines after smoothing:

It is
accessible through:
PROCESSING
→ DTM
PROCESSING
→ ISOLINES SMOOTH...
1.
Select Input
Layer:
-
Use combobox or
to select the layer containing the isolines that will be smoothed .
2. Target
Scale: enter the scale value and click on the OK button
beside the field.
3. Simplification
Factor: this value will be used to do an input line
filtering.
Enter the wanted value in meters.
4. Maximum
Distance: this value will define distance among simplified
line
points. Enter the value in meters.
5. Simplify
output:
click on
this box if after lines being smoothed they will pass through
Douglas_Peuckher simplification method using tolerance for
simplification.
6. Set
Output SRS

to select output layer SRS.
7.
Inform the Output Repository
by clicking on:
7.1.

to select the output
directory
and also inform the new layer name to store the result, or
7.2. 
to select
the Data Source
and Inform
the new
Layer
Name to store the aggregation result.
8. Click OK
to perform the
operation or Cancel to close the interface.