[ncl-talk] unmatched lats/lons on plotted map

[Setareh Rahimi]

Dear Rick & Dennis,
So many thanks for your help. It was so efficient.
Best wishes,

On Sat, Feb 26, 2022 at 2:22 AM Dennis Shea <shea at ucar.edu> wrote:

> Expanding on Rick's post
> ===
> There are several functions that can be used.
>
> Two are:
>    (1)  *getind_latlon2d*
> <https://www.ncl.ucar.edu/Document/Functions/Contributed/getind_latlon2d.shtml>
> <== get the index values if the four nearest grid points to the user
> specified location(s)
>                                                  return the values of the
> nearest grid point location. No interpolation is performed.
>    (2)  *rcm2points_Wrap*
> <https://www.ncl.ucar.edu/Document/Functions/Contributed/rcm2points_Wrap.shtml>
> <== use the four nearest grid points and use bilinear interpolation to
> obtain values at the user specified location(s)
>
> ===
> I modified Rick's code to use each function:
>
> [1]
>       %>  ncl *extract-LatLonAOD_getind_latlon2d.ncl     *==>
> aod-siri.getind_latlon2d.txt
> [2]
>       %>  ncl *extract-LatLonAOD_rcm2pts.ncl*                  ==>
> aod-siri.rcm2points.txt
>
>
> BOTH scripts have many print statements to facilitate understanding the
> flow. Please examine the outputs.
> ------------------------
> aod-siri.rcm2points.txt  contains values bilinearly interpolated using the
> 4 nearest grid points
>
> 00001 2015040106   25.90    54.55    0.39799
> 00002 2015040112   25.90    54.55    0.40869
> 00003 2015040118   25.90    54.55    0.35409
> 00004 2015040200   25.90    54.55    0.46902
> 00005 2015040206   25.90    54.55    0.55770
> 00006 2015040212   25.90    54.55    0.33024
> 00007 2015040218   25.90    54.55    0.10930
> 00008 2015040300   25.90    54.55    0.06019
> ----------------------
>
> aod-siri.getind_latlon2d.txt   contains values at the nearest  grid point
>
> 00001 2015040106   25.91    54.56    0.39773
> 00002 2015040112   25.91    54.56    0.40965
> 00003 2015040118   25.91    54.56    0.35460
> 00004 2015040200   25.91    54.56    0.46916
> 00005 2015040206   25.91    54.56    0.55682
> 00006 2015040212   25.91    54.56    0.32912
> 00007 2015040218   25.91    54.56    0.10935
>
> ================
>
>
>
>
>
>
>
> On Fri, Feb 25, 2022 at 10:35 AM Rick Brownrigg via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
>> I'm not certain about extracting the values at specific locations. It
>> looks like you were on the right track (at least, a solution that works).
>> I've attached a very slightly modified version of the script fragment you
>> sent. I made the variables lon_pts/lat_pts proper arrays (lines 6-7), and
>> then closed the do-loop so the script is syntactically correct (line 30).
>> The indices returned by getind_latlon2d() seem to be about right, as seen
>> by the added print statement at line 24.
>>
>>  Hope that helps...
>> Rick
>>
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>
>

-- 
S.Rahimi
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