Re: [ferret_users] Filling in the blanks with interpolation

[Martin Schmidt <mschmidt@xxxxxxxxxxxxxxxxx>]

Hi,
this question was asked repeatedly. Ferret offers methods
for filling zonally or meridionally. The results are not 
always satisfying. 

I have written an external function, which provides two-dimensional
filling. If a point is missing, it is filled with an appropriate 
average over the nearest neigbours. This is repeated, until all 
points are filled. A mask can prohibit filling of selected areas
and the number of cycles may be limited. Some tricks are needed
to prevent artificial structures, because this scheme is a 
"cellular automaton". 

The code is ready for compilation with the external function tools
of ferret. I have implemented it in the AIX-Version 5.41. Some 
adaption of the subroutine names will be needed, because C and
Fortran with AIX require a special handling of underscaores in the
end of function names. This should be simple, because examples 
for external functions are delivered with ferret.

If someone is interested in this code and is able to create
external functions, I would send out the code. It would be great
to have it in a future release of ferret. I have found it
very useful as a simple and robust tool to fill gaps in various datasets.

Greetings,
Martin Schmidt