[ferret_users] Problems determining indices using CURV_TO_RECT_MAP

[John Schattel <john.schattel@xxxxxxxx>]

Hello All,

I am trying to use CURV_TO_RECT_MAP to determine the index values of a 
subgrid for a curvilinear dataset using the  FAQ 
http://www.ferret.noaa.gov/Ferret/FAQ/custom_plots/subsetting_curvi_data.html.  
When I implement the outlined procedure, Ferret crashes (see below).  
Any thoughts on what might be going wrong?

In advance, thanks for any help you can provide.

John

bash-2.05b$ ferret
       NOAA/PMEL TMAP
       FERRET v5.81
       Linux(g77) 2.4.21-32 - 07/13/05
       29-Aug-05 16:29

yes? go hazmat_subgrid
! Input data on a curvilinear grid
use "http://localhost/cgi-bin/nph-dods/dgom/hazmat.nc";
*** NOTE: Units on axis "sigma" are not recognized: sigma_level
*** NOTE: They will not be convertible:

let lonin = lon[d=1]
let latin = lat[d=1]

! Define the corners of our subset: These will define
! the axes of our output grid

let xmin = -90
let xmax = -82
let ymin = 25
let ymax = 29

def axis/x=`xmin`:`xmax`/npoints=2/modulo/units=degrees xax
!-> def axis/x=-90:-82/npoints=2/modulo/units=degrees xax
def axis/y=`ymin`:`ymax`/npoints=2/units=degrees yax
!-> def axis/y=25:29/npoints=2/units=degrees yax

!  Define a variable on the output grid

let lonlatout = y[gy=yax] + x[gx=xax]

! Compute weights for the mapping

set memory/size=250
Cached data cleared from memory
let map = curv_to_rect_map (lonin, latin, lonlatout, .5)

! The variable <I>map</I> includes the indices within the source
! grid which correspond to coordinates in the destination grid.
! These are the lower lon and lat and upper lon and lat indices:

! e.g. here are the longitude indices (L=2) and latitude indices (L=3)
! the four nearest neighbors (K=1:4) in the curvilinear grid, which map
! to the i=1,j=1 location on the output axes.

! Compute the minimum and maximum indices in I and J needed
! to plot the entire region

show grid map
   GRID (G005)
name       axis              # pts   start                end
XAX       LONGITUDE            2mr   90W(-90)             82W(-82)
YAX       LATITUDE             2 r   25N                  29N
ABSTRACT  Z              9999999 r   1                     9999999
ABSTRACT  T              9999999 r   1                     9999999

let llon = map[i=1,j=@min,l=2,k=@min]
list map[i=1,j=@min,l=2,k=@min]
            VARIABLE : CURV_TO_RECT_MAP (LONIN, LATIN, LONLATOUT, .5)
            LONGITUDE: 90W(-90)
            LATITUDE : 23N to 31N (minimum)
            Z        : 0.5 to 4.5 (minimum)
            T        : 2
         91.00
let llat = map[i=@min,j=1,l=3,k=@min]
list map[i=@min,j=1,l=3,k=@min]
            VARIABLE : CURV_TO_RECT_MAP (LONIN, LATIN, LONLATOUT, .5)
            LONGITUDE: 94W(-94) to 78W(-78) (minimum)
            LATITUDE : 25N
            Z        : 0.5 to 4.5 (minimum)
            T        : 3
         73.00

let ulon = map[i=2,j=@max,l=2,k=@max]
list map[i=2,j=@max,l=2,k=@max]
free(): invalid pointer 0xa193d70!
            VARIABLE : CURV_TO_RECT_MAP (LONIN, LATIN, LONLATOUT, .5)
            LONGITUDE: 82W(-82)
            LATITUDE : 23N to 31N (maximum)
            Z        : 0.5 to 4.5 (maximum)
            T        : 2
         183.0
let ulat = map[i=@max,j=2,l=3,k=@max]
list map[i=@max,j=2,l=3,k=@max]
Segmentation fault