If the grid is not a rectangular lat/lon grid then the conventions
described in section 5.2 need to be used. This provides for 2D lat/lon
arrays. Section 5.6 also applies to your data, and the example for Lambert
conformal projection is probably very close to what you need. The only
thing missing is the definition for the Azimuthal Equidistant Projection
which is not currently contained in Appendix F. I propose adding the
following entry to Appendix F:
---------------------------------------------------------------------------
Azimuthal equidistant
grid_mapping_name = azimuthal_equidistant
Map parameters:
* longitude_of_projection_origin
* latitude_of_projection_origin
* false_easting
* false_northing
Map coordinates: The x (abscissa) and y (ordinate) rectangular coordinates
are identified by the standard_name attribute values
projection_x_coordinate and projection_y_coordinate respectively.
Notes: Notes on using the PROJ.4 software package for computing the mapping
may be found at
http://www.remotesensing.org/geotiff/proj_list/azimuthal_equidistant.html
---------------------------------------------------------------------------
Brian
On Mon, Feb 27, 2006 at 06:08:24PM +0100, sdj at tiscali.it wrote:
> Dear All,
>
> Please accept my apologies for yet another querie.
>
> I have browsed through the documentation to find the way to represent
> data in Azimuthal Equidistant Projection, but unfortunately had no
> success.
>
> Considering I have two arrays which specifiy the values of my
> longitudes and latitudes, how do I represent my data ?
>
> With a simple equidistant cylindrical projection I had the following
> notation:
>
> dimensions:
> longitude = x ;
> latitude = y ;
> variables:
> float longitude(longitude) ;
> longitude:standard_name = "longitude" ;
> longitude:long_name = "Longitude" ;
> longitude:units = "degrees_east" ;
> longitude:step = "lon_delta" ;
> longitude:valid_min = "lon_min" ;
> longitude:valid_max = "lon_max" ;
> longitude:axis = "X" ;
> float latitude(latitude) ;
> latitude:standard_name = "latitude" ;
> latitude:long_name = "Latitude" ;
> latitude:units = "degrees_north" ;
> latitude:step = "lat_delta" ;
> latitude:valid_min = "lat_min" ;
> latitude:valid_max = "lat_max" ;
> latitude:axis = "Y" ;
> short variable_mean(latitude, longitude) ;
> variable:standard_name = "standard_name" ;
> variable:units = "units" ;
> variable:cell_method = "mean (interval: 1 month)" ;
> variable:scale_factor = "scale_factor" ;
> variable:add_offset = "offset" ;
> variable:valid_min = "valid_min" ;
> variable:valid_max = "valid_max" ;
> variable:missing_value = "missing_value" ;
>
> What do I need to do in order to construct a netCDF file following the
> CF conventions for data projected on an azimuthal equidistant
> projection.
>
> Many thanks for your help.
>
> Best Regards,
> Pepe
>
>
>
>
> Tiscali ADSL 4 Mega Flat
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Received on Mon Feb 27 2006 - 18:23:26 GMT
