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

Rick Brownrigg brownrig at ucar.edu
Fri Sep 11 08:18:40 MDT 2020

```Hi,

No, not in meters -- you're trying to find the indices of the grid cells
that correspond to the corners of your smaller domain. For instance, what
are the values i,j that correspond to the corner (-10N,44.5E)

RB

On Fri, Sep 11, 2020 at 8:11 AM Geeta Geeta <geetag54 at yahoo.com> wrote:

> Soory Mr Rick. It is not clear to me.
>
> 4 corners of large  domain are  (-10N,44.5E) , (-10,105.5), (45.5,105.5),
> (45.5,44.5).
> I want small domain to be 10-20N/70-75E.
> So I have to calculate the X Y (distance in meters)?.
> kindly clarify .
>
> Geeta.
>
>
>
>
>
>
>
>
>  On Friday, 11 September, 2020, 07:20:57 pm IST, Rick Brownrigg <
> brownrig at ucar.edu> wrote:
>
>
>
>
>
>  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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