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Re: GrADS IOSP
- Subject: Re: GrADS IOSP
- Date: Tue, 22 Feb 2011 07:03:06 -0700
On 2/17/2011 12:32 PM, Don Murray wrote:
John-
Many people here write out their data in grads binary files. I'd like
to view them in the IDV, so am working on an IOSP for this. I plan on
using the GridServiceProvider framework that I used for the GEMPAK and
McIDAS grid readers. At this point, I'm only going to handle lat/lon
grids.
One question I have is about the RandomAccessFile that gets passed to
the IOSP. For grads, there is a data description file (sometimes
called the ctl file) which describes the structure of the binary data
file (see: http://www.iges.org/grads/gadoc/descriptorfile.html). I've
attached a sample CTL file. My idea is that the user would open the
ctl file which would set up the grid structure for the
GridServiceProvider, but when the data is read, it reads from the
binary file described in the ctl file. So, the initial
RandomAccessFile would be the CTL, but I'm wondering about accessing
the binary file. Do I just hold a handle internally to a
RandomAccessFile and read from that? Are there other IOSPs that
handle metadata in one file and the data in another that I could use
as a guide?
An IOSP is free to open other files, just make sure they get closed on
the close(). check for the existence of the binary file on the
isValidFile() but dont open it until open() is called. You cant keep
any state from the isValidFile() method.
GRIB uses index files which are seperate files. Im working on
ucar.nc2.iosp.noaa.Ghcnm which is also experimenting with index files.
As usual, dont have any great examples.
I also have to figure out where this IOSP lives. Right now I'm just
coding in ucar.nc2.iosp.grads (won't check it in until it works), but
since the code is not being developed at UCAR, I'm not sure I want to
use your licensing which gives all copyright/licensing to UCAR.
Its up to you. If you want to contribute it back, we would need a
compatible license. If you do that, you basically give rights to fork
the code (i think), in which case i dunno if copyright matters all that
much. but i assume you can make copyright anything you want.
Thanks for an help you can give.
Do you want to meet for lunch or a walk next week?
I have my daughter coming in for a visit. let me see what my schedule
looks like. A walk sounds good.
Don