I tried to get example x21c to work properly on
Windows, using the CSA library. Unfortunately it returns
only zero values as interpolation results.
In the process I noticed that some of the other methods
rely on the index array to have been filled before!
For instance: grid_nnaidw() uses the (static) array
"index" to determine the neighbours, but the function
that fills that array (either dist1() or dist2()) is not called
in that routine.