[netCDF #WJK-294679]: Regarding projections of a netcdf file

Hi Naveen,

> I am new to netcdf data format.How to know the projection of a netcdf
> file.The grid types
> 
> shum.1948.nc
> 
> <https://docs.google.com/file/d/0B1Hf3oUhHj5tS0NxS0VmYjdxRGM/edit?usp=drive_web>
> 
> of  netcdfs file i am having with me is global lon lat and gaussian grids.
> 
> I wanted to retrive data from the netcdf file using Arc GIS 9.3. So,
> in arcgis 9.3, I need to give projections like lambert conformal conic
> etc.my doubt is
> 
> 1. Is global lon lat grid is same as WGS 1984.
> 2. How do i know the projection of a given netcdf file.
> 
> I am here by attaching a netcdf file below.Pls say its projection.

The netCDF file you attached is defined on a latitude-longitude grid, and no
projection is specified, so it's a spherical earth.  The only parameter needed 
for
such a coordinate system is the assumed earth radius, which isn't specified
in the file you attached.  The standard way to specify coordinate reference 
systems including earth radius or other projection parametrs for netCDF files 
is by using the CF Conventions, in particular see section 5.6 on horizontal 
coordinate systems in:

  http://cfconventions.org/

The data you attached uses an older convention, "COARDS", which doesn't
have a standard way to identify projections or coordinate systems:

  http://ferret.wrc.noaa.gov/noaa_coop/coop_cdf_profile.html

With such a coarse global grid and an assumed spherical earth, what you use
for earth radius probably doesn't matter much, so you could probably safely
assume something like 6371000 meters.

--Russ

Russ Rew                                         UCAR Unidata Program
address@hidden                      http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: WJK-294679
Department: Support netCDF
Priority: Normal
Status: Closed