.ctl for MODIS HDF file

[Jennifer Adams]

I can't allow misinformation to go out to the list uncorrected: GrADS
can read any HDF file containing gridded fields.
This particular HDF file contains swath data. It's gridded -- there
are 406 cells in the along-swath direction, and 270 cells in the
across-swath direction. GrADS will read this data, but only onto an
abstract x,y grid. The lat/lon values of each grid point are read in
as data variables. A full 'dtype hdfsds' descriptor file would include
the following lines:

xdef 270 linear 1 1
ydef 406 linear 1 1
tdef 1 linear ...
...
vars 4
Latitude=>scanlat 0  y,x  Geodetic Latitude
Longitude=>scanlon 0 y,x Geodetic Longitude
Scan_Start_Time=>scantime 0 y,x International Atomic Time at Start of
Scan replicated across the Swath
Surface_Temperature=>tsfc 0 y,x Surface_Temperature
endvars

You can add more variables, including some that have a Z axis,
depending on what you'd like to look at in the file. The rest of the
required descriptor file entries are discussed in the documentation
page http://iges.org/grads/gadoc/SDFdescriptorfile.html

--Jennifer


On Oct 19, 2009, at 10:49 AM, Yan Libin wrote:
> a ctl is not enough

On Oct 19, 2009, at 10:49 AM, Jayakrishnan PR wrote:
> ... we cannot open them through grads by writing a ctl file.


On Oct 19, 2009, at 10:26 AM, Hao He wrote:

> Hi,
>  I want to read MODIS HDF file by GrADS. Unfortunately both sdfopen
> and
> xdfopen do not work for me, so I need to write a complete .ctl file.
> But

> I am confused after reading the MODIS data set
> (http://modis-atmos.gsfc.nasa.gov/MOD07_L2/format.html)

> I am wondering if anyone has experience on it.
> Thanks a lot!
>
> Hao
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