Thank you for correcting my mistake. I forgot to make XDim and YDim
coordinate variables.
However, my question still remains. Regardless of this modification, ncdump
can open and dump data. However, I don't know if this is standardized way
and netCDF4 recognizes "lon" and "lat".
Thanks,
Choonghwan Lee
-----Original Message-----
From: tomw.ssec@xxxxxxxxx [mailto:tomw.ssec@xxxxxxxxx] On Behalf Of Tom
Whittaker
Sent: Thursday, April 03, 2008 6:47 PM
To: Choonghwan Lee
Cc: netcdfgroup@xxxxxxxxxxxxxxxx
Subject: Re: [netcdfgroup] 2D coordinate variables
If I am not mistaken, you need to define your variable XDim and YDim
as the "coordinate variables", such that the ncdump (or equivalent)
shows:
XDim(XDim);
YDim(YDim);
See section 5.2 of the CF 1 conventions in the document you referenced.
Hope that helps.
tom
On Thu, Apr 3, 2008 at 4:59 PM, Choonghwan Lee <cholee@xxxxxxxxxxxx> wrote:
> Hello,
>
> While converting HDF-EOS2 files to files that can be read by netCDF4, I
got
> a question regarding coordinate variables. There is a variable that has
two
> coordinate variables: XDim and YDim. I found the following webpage
defines
> what coordinate variable is, but it doesn't mention my case.
>
>
https://www.unidata.ucar.edu/software/netcdf/guidec/guidec-7.html#HEADING7-6
> 7
>
> The problem is that longitude and latitude cannot be represented as 1d
> array. To handle this, I referred to CF convention which can be found
from
>
>
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.1/cf-conventions.html#id
> 2617539
>
> According to the above convention, I generated a file like the following:
>
> group: Data Fields {
> dimensions:
> XDim = 2400 ;
> YDim = 2400 ;
> variables:
> ubyte Snow_Cover_Daily_Tile(YDim, XDim) ;
> Snow_Cover_Daily_Tile:coordinates = "lon lat" ;
> double lon(YDim, XDim) ;
> double lat(YDim, XDim) ;
>
> It seems this file is a legal netcdf4 file in that ncdump in the latest
> netCDF4 snapshot does not reject this file. However, I'm wondering if
netcdf
> library recognizes "coordinates" attribute and relates "lon" and "lat" as
> coordinate variables. If netcdf library does not recognize them, is there
> any standardized way to inject two-dimensional coordinate variables? I
read
> one draft written in 1997, but I have no idea if this draft was
published.
>
>
> Thanks,
> Choonghwan Lee
>
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--
Tom Whittaker
University of Wisconsin-Madison
Space Science & Engineering Center (SSEC)
Cooperative Institute for Meteorological Satellite Studies (CIMSS)
1225 W. Dayton Street
Madison, WI 53706 USA
ph: +1 608 262 2759
