[ncl-talk] unable to extract data and plot it for a smaller domain.

[Rick Brownrigg]

Hi,

I *think* the trick here is to compute the i,j indices of the grid that
correspond to your smaller domain. Since it's a mercator projection, and
the original domain is relatively small (60x60 degs), I would think you
could get decent results by using a simple linear scaling to find those
values. So if the grid is NxM (LatxLon), and you extract the min/max
lat/lons from the attributes into variables minLon, maxLon, etc.,  then
something like:

  minI = tointeger( minLonSmallerDomain * (M -0) / (maxLon - minLon) )  ;
truncating
  maxI = tointeger( maxLonSmallerDomain * (M -0) / (maxLon - minLon) )
...similarly for Y...

and then:

 Plot(0)                           =
gsn_csm_contour_map(wks,TIR1_INVERTED(0,minJ:maxJ,minI:maxI),rescount)

and don't forget to substitute appropriate values into the
mpLeft/RightCornerLat/LonF resources.

Does that make sense?

Rick


On Fri, Sep 11, 2020 at 4:22 AM Geeta Geeta via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Hi.
>
> I have satellite data which has a resultion of 4 km (TIR1) and there is projection information provided in the datafile.
> integer Projection_Information ( DIM_000 )
>         DIMENSION_LIST :    <ARRAY of 0 elements>
>         false_easting :      0
>         false_northing :      0
>         grid_mapping_name :    mercatorpor Brightness Temperaturerature
>         longitude_of_projection_origin :      75
>         lower_left_lat_lon(degrees) :    (  -10, 44.5 )
>         lower_right_lat_lon(degrees) :    (  -10, 105.5 )
>         semi_major_axis :    6378137
>         semi_minor_axis :    6356752.3142
>         standard_parallel :    17.75
>         upper_left_lat_lon(degrees) :    ( 45.5, 44.5 )
>         upper_left_xy(meters) :    ( -3234623.003937, 5401854.420193 )
>         upper_right_lat_lon(degrees) :    ( 45.5, 105.5 )
> The lat/lon are not provided.
>
> Plotting the TIR1 (count), radiance and Brightness temperature for the entire domain is happening by using information from the Projection info.
> This INFO is used from the Line numbers 109-114 of the code.
>
> My questions are 1. I am Not able to plot the data for a smaller domain of
> my ineterst
>
>                           2. since I am unable to attch the lat/lon arrays to the variables, I am unable to plot the data for a smaller domain and unable to write the data for a smaller domain of my intererst.
> the Images are attached.
>
>
> Request someone to help me.
>
> Geeta._______________________________________________
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