# Re: Plotting CONUS data with NCL with only having the lat/lon points

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Fri Feb 08 2013 - 12:54:43 MST

Actually, not well known because 99.9% of the examples
use gridded data, you can use gsn_csm_contour_map with
'random' (station) data.

See Example 1 at:
http://www.ncl.ucar.edu/Applications/station.shtml
==============================================================
There is no need to put the original data into a netCDF file.
Assuming, -1 is a missing value and the 3 sample lines
you sent are named "hrapy.txt"

data@_FillValue = -1.0

lat = data(3::6)
lon = data(4::6)
val = data(5::6)
delete(data) ; not necessary

;print(lat+" "+lon+" "+val) ; print all values (too long)
print(lat(:9)+" "+lon(:9)+" "+val(:9)); print 1st 10 values

iGood = ind(.not.ismissing(val)) ; subscripts of good values

:
:
res@sfXArray = lon(iGood)
res@sfYArray = lat(iGood)

map = gsn_csm_contour_map(wks,val(iGood),res)
================================================================

When the variable passed to ' gsn_csm_contour_map ' is one dimensional
then the sf{X/Y}Array resources must be set to the appropriate values.
A proprietary software function is used to efficiently perform the
plotting.

D

02/08/2013 12:17 PM, James Scott - NOAA Affiliate wrote:
> Arthur,
>
> You can't use "gsn_csm_contour_map" map with station data. It expects
> the data to be on a monotonically increasing grid. You will have to
> interpolate your station data to a regular lat/lon grid before using
> "gsn_csm_contour_map". I recommend using the "natgrid" function to
> interpolate.
> http://www.ncl.ucar.edu/Document/Functions/Built-in/natgrid.shtml
>
> -Jamie
>
> On Fri, Feb 8, 2013 at 12:00 PM, <ncl-talk-request@ucar.edu
> <mailto:ncl-talk-request@ucar.edu>> wrote:
>
> Hi,
>
> I am trying to plot observed rainfall data from the NOAA's River
> Forecast
> original
> data came on an HRAP grid/format. It had to be decoded from a netcdf
> file
> to ascii text file. The text file gives the observed value of
> precip. for
> each lat/lon point. How can I plot data that only has it's lat/lon
> reference?
>
> The data looks like this with value being the precip. variable:
>
>
> "id", "hrapx", "hrapy", "lat", "long", "value"
> 0, 14, 10, 23.496319, -118.658440, -1.000000
> 0, 15, 10, 23.503891, -118.624420, -1.000000
>
>
>
> I tried putting the data into a netcdf file, then using the
> "gsn_csm_contour_map" function/tool to do it, but I got a segmentation
> fault error. I was using NCL 5.1.0, and saw that this NCL version
> can only
> handle variables no larger than 2 GB. So, I downloaded NCL version
> (6.1.1),
> and I still get the same error (segmentation fault). The size of
> each .nc
> file for the CONUS is 20507540 bytes which is not 2 GB.
>
> Do you have and insight as to how I could solve this issue? It does not
> seem hard to do.
>
> -Arthur Eiserloh
>
>
>
>
>
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Received on Fri Feb 8 12:54:54 2013

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