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Re: [ferret_users] Extracting data/value from grided data in rotated Mercator projection

Hi Jagadish,
It depends on the way  your grid is listed in the file. Is it coming in on a curvilinear grid?  that is, when you SHOW DATA, are the longitudes and latitudes 2-dimensional variables, similar to this?

yes? show data
     currently SET data sets:
    1> /home/porter/ansley/ans_ferret/curvi/ht_cf.nc  (default)
 name     title                  I         J         K         L
 GEOLON geographic longitude   1:180     1:173     ...       ...
 GEOLAT geographic latitude    1:180     1:173     ...       ...
 VAR     topography            1:180     1:173     ...       ...

If this is the case then you will need to use the SAMPLEXY_CURV function to get the value of the variable at the location in the curvilinear coordinate grid. 

If the variable is a simple variable on a set of coordinate axes defined in longitude and latitude, but irregularly spaced, such as

yes? show data
    2> /home/ansley/data/var.nc  (default)
 name     title                  I         J         K         L
topography             1:180     1:90      ...      ...

yes? show grid sst    GRID GCOADS
 name       axis              # pts   start                end
 LON       LONGITUDE          180mr   21E                  19E(379)
 LAT       LATITUDE            90 i   89S                  89N
 normal    Z
 normal    T

Then you can just say

yes? list/x=80/y=20 var


jagadish karmacharya wrote:
Hi everyone,

I have grided data in rotated Mercator projection. I can properly plot that data using map projection information. I want to know if I need to extract value at  a location say 80E, 20N
it is enough to load the data and just issue  list/x=80/y=20 var command? Does it take care of the shift we see in the map plot automatically? In other word, the shift we see in map plot is limited to  map plot only or is there similar shift in data reading/extraction. If there is some shift how to extract data  in real world coordinate (at the grid with  80E, 20N in above case)


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