id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
120	Thinning short profiles	Dave Offiler	Dave Offiler	"From Axel von Engeln 15:30 19/6/2007:
{{{
Previous versions would not thin when less than the requested thinned
levels were given in the unthinned data. So, assuming I want 247 levels
back, but only have 120 in the unthinned data, the thinner would return 120
levels, without modifications to the data. This is of course one of those
annoying extreme cases and should not happen under normal circumstances,
but we currently have this kind of data in some Christian's offline
processor.

Anyway, for batch processing this is not very useful, so what I do now is
to return the 247 levels, but set them all to missing. That was the easy
way to implement this kind of trouble, the more accurate would be to use
the 120 levels and actually thin them were they are providing data. I leave
this update to you if you can bother (as said, should not really happen in
reality if all works well).
}}}

Axel reports that a few GRAS profiles can be generated with only a small number of vertical samples (say 120). The SAMPLE thinning method obviously does not sub-sampling if the user requests (or defaults) to a max. no of output samples greater than the input - ie it would output  the origianl 120 samples. The interpolation methods behave in the same way; any profile with less than the (nominal) 247 samples is unthinned and will also output the 120 samples unchanged.

Axel requests that the 120 samples be mapped onto the 247 fixed levels (thus in effect increasing data volume rather than decreasing it, which latter was the objective of doing the thinning!). However, in this case, mapping all profiles to a common set of fixed levels is the objective for validation purposes. Axel has made a local fix to fill all 247 samples with missing data in these cases.

I consider the existing behavour to be expected - this is not a bug but a 'feature change' request, and a non-urgent minor issue to be investigated when resources allow. "	enhancement	closed	normal	3.0	ropp_io	1.0	fixed	Thinning