masking

[Matthias Fripp]

Wow, you used almost exactly the same approach I suggested (but with
more Fortran and less Excel)! Glad to know I was on to something.

I'm not fluent in Fortran, so I had trouble deciphering the
cr_mask_fl.f program that converts an ASCII list of points into an
ASCII masking file that GRADS can read. Would you be able to send a
sample of the final ASCII masking file that you produced and the
command you use to load it into GRADS? Or if there's an obvious place
to look in the instructions, that would be great too. So far I only
know how to get GRADS to read local or remote binary files. It would
be great to have a way to display data from ASCII/text files that I
create myself.

Best,

Matthias

On Oct 28, 2009, at 8:39 AM, Rupak Rajbhandari wrote:

> Hi,
>
> Creating a masking file is not a simple procedure. Here I am sending
> you a masking instruction I prepared (last year  for small training
> group in Nepal). The masking file is for 0.1 resolution, so you need
> to edit a little. The attached RAR file consists of a instruction
> file and two fortran programs. In addition you will need ArcView GIS
> and India shape file (boundary polygon) and fortran compiler. You
> should first edit the program to suit your resolution. The rest
> should be clear from the instruction file.
>
> Once the masking file has been created, simply replace the master
> file with undefined values where grid point point values are zero in
> the masking file.
>
> Hope it helps!
>
> -rupak
>
>
>
>
>
> On Tue, Oct 27, 2009 at 9:04 PM, Matthias Fripp <matthias.fripp at eci.ox.ac.uk
> > wrote:
> It sounds like you will need to do something like this:
>
> 1. Create a file listing all the grid points in or near India (e.g.,
> within a simple latitude and longitude range that covers all of
> India and some surrounding areas).
>
> 2. Import this list into a GIS program and intersect it with India's
> land area.
>
> 3. Export a list of Indian grid points from the GIS program.
>
> 4. Import this list into GRADS.
>
> Step 1 would be easy to do, e.g., in a text (.csv) file created in
> Excel, if your grid is regularly spaced.
>
> Step 2 and 3 are easy if you have a GIS program and difficult
> otherwise. I could help you with that if you want.
>
> I don't know how you would do Step 4. I can easily create a text
> file listing all the relevant points, but I don't know how you would
> reference that text file from GRADS to create a mask variable.
> Anyone else have ideas about this?
>
> Matthias
>
> On Tue, Oct 27, 2009 at 7:23 AM, Sachin Ghude <sachinghude at tropmet.res.in
> > wrote:
> Hi,
>
> I want to plot tropospheric NO2 only over the Indian grid points
> (not Nepal, Pakistan
> and BanglaDesh). Is there any such utility so that it will enable me
> to plot data only
> for  India girds in GRADs. ( my grid size is 0.25 x 0.25 degrees).
>
> please do the needful..
>
> bye..
>
> Sachin
>
>
> <masking.rar>

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