17.30. Interpolation and contouring
Module contributed by Paolo Cavallini - Faunalia
This chapter shows how to use different backends to calculate different interpolations.
The project shows a gradient in rainfall, from south to north.
Let’s use different methods for interpolation, all based on vector
Set cell size to 500 for all analyses.
[Inverse distance to a power; Power: 4; Search radius: Global; Search range: all points]
Then measure variation among methods and correlate it with distance to points:
[Unselect Propagate NULLs, Aggregate operation: stddev]
Thus, areas far from points will have less accurate interpolation.
Various methods to draw contour lines [always step= 10] on the stddev raster:
[NB: in some older SAGA versions, output shp is not valid, known bug]