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

Geeta Geeta geetag54 at yahoo.com
Fri Sep 11 08:41:15 MDT 2020

the NxM grid is the larger grid,  of the size 55N and 61E.
will it be minI  = 70* 61/(105.5-44.5) ??

does not seem to be correct, I am not achieving anything

Geeta.

On Friday, 11 September, 2020, 07:48:54 pm IST, Rick Brownrigg <brownrig at ucar.edu> wrote:

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._______________________________________________

ncl-talk mailing list

ncl-talk at mailman.ucar.edu

List instructions, subscriber options, unsubscribe:

https://mailman.ucar.edu/mailman/listinfo/ncl-talk