[ferret_users] Missing values - interpolation and smoothing

[Szymon Roziewski <szymon.roziewski@xxxxxxxxx>]

Dear Ferreters,
I have such a problem, namely I have data hs as an array (132,145) from hs.cdf file with missing value set as -999.
Then I read those data and try to interpolate (regridding with smoothing). The script follows as:
use hs.cdf
DEFINE AXIS/X=-5.666666667:5.25:0.010416667 xfine 
DEFINE AXIS/Y=-2.0:10.0:0.010416667 yfine 
DEFINE GRID/x=xfine/y=yfine fine_grid 
let/bad=-999 var_hs=hs[i=1:132,j=1:145,k=0,l=1]
let/bad=-999 fine_hs=var_hs[gxy=fine_grid] 
LET/bad=-999 ubox_hs=fine_hs[x=@SBX:19,y=@SBX:19] 
LET/bad=-999 utaper_hs=ubox_hs[x=@SHN:13,y=@SHN:13] 
shade/levels=(0.0)(0.5,1,0.5)(1.0,1.25,0.25)(1.25,2.0,0.75)(2.0,7.0,1.0)(7.0,11,2.0)(15) utaper_hs[g=fine_grid]
frame/file=dd.gif
What I get is completely frustrating me.
I think the missing value doesn't work well. And that's why the interpolation gives such a misleading result on the boundary.
I attach demanded files: hs.cdf and also hs.gif.

I appreciate any help.
Thank You in advance.

Attachment: hs.cdf
Description: Cdf file

Attachment: hs.cdf
Description: Cdf file