Hey David,
ferret warns you, because you didnt put in the exact coordinate, so it chooses the closest point:
yes? shade/y=0 temp[d=2]-temp[d=1]
*** NOTE: Ambiguous coordinates on Z axis: TEMP[D=2]-TEMP[D=1]
yes? shade/y=0.5 temp[d=2]-temp[d=1]
yes? shade/y=-0.5 temp[d=2]-temp[d=1]
Ferret doesnt say a note, when you put command y=0.5 or y=-0.5 as these are valid points:
yes? show grid temp[d=1]
GRID GMS1
name axis # pts start end
XAXLEVITR LONGITUDE 360mr 20.5E 19.5E(379.5)
YAXLEVITR LATITUDE 180 r 89.5S 89.5N
ZAXLEVITR DEPTH (m) 20 i- 0 5000
normal T
For command y=0, ferret somehow chooses the y=-0.5 (0.5S). i dont know why not the y=0.5 (0.5N). But thats an other topic.
Peter
On Thu, Oct 2, 2008 at 5:41 PM, David Wang
<climater@xxxxxxxxx> wrote:
Hi Ferreters,
It seems to me that if I load two netcdf files whose variables have the identical vertical axis, Ferret will still render them as different ones, and issue a warning message ("*** NOTE: Ambiguous coordinates on Z axis") when calculations are done among variables. I guess calculations are correctly done, but the message is somewhat misleading. Here is an illustrative example:
$ ln -s $FER_DSETS/data/levitus_climatology.cdf .
$ ferret
NOAA/PMEL TMAP
FERRET v6.1
Linux(g77) 2.4.21-32 - 03/25/08
2-Oct-08 11:10
yes? use "$FER_DSETS/data/levitus_climatology.cdf"
yes? use "./levitus_climatology.cdf"
yes? say `temp[d=1],return=zaxis`
!-> MESSAGE/CONTINUE ZAXLEVITR
ZAXLEVITR
yes? say `temp[d=2],return=zaxis`
!-> MESSAGE/CONTINUE ZAXLEVITR1
ZAXLEVITR1
yes? shade/y=0 temp[d=2]-temp[d=1]
*** NOTE: Ambiguous coordinates on Z axis: TEMP[D=2]-TEMP[D=1]
Thanks,
David