Re: [netcdf-java] Data in British National Grid coordinates

• To: netcdf-java@xxxxxxxxxxxxxxxx
• Subject: Re: [netcdf-java] Data in British National Grid coordinates
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Wed, 14 Mar 2012 15:49:56 -0600

Hi Jon:

It should understand transverse_mercator, see

http://www.unidata.ucar.edu/software/netcdf-java/reference/StandardCoordinateTransforms.html

you might also want UTM which is not CF compliant.

if you send the file, i can check whats the problem.

John

On 3/14/2012 3:41 PM, Jon Blower wrote:

Hi,

Does NetCDF-Java understand the "British National Grid" CRS 
(http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#british-national-grid)?
  A user of ncWMS has data in this CRS and nj seems to treat it as a generic curvilinear 
grid (the latest 4.2 version of ToolsUI seems to confirm this if I'm using it correctly).

I've put the CDL header of the dataset at the end of this email.  This seems to 
match the CF documentation, unless I've missed something.

TIA,
Jon

netcdf file:C:/Users/Jon/Desktop/test.ncml {
  dimensions:
    X = 2000;
    Y = 2000;
    lat = 4000000;
    lon = 4000000;
  variables:
    double X(X=2000);
      :standard_name = "projection_x_coordinate";
      :units = "m";
    double Y(Y=2000);
      :standard_name = "projection_y_coordinate";
      :units = "m";
    float lat(Y=2000, X=2000);
    float lon(Y=2000, X=2000);
    float variable(Y=2000, X=2000);
      :coordinates = "lat lon";
      :grid_mapping = "crs";
    int crs;
      :grid_mapping_name = "transverse_mercator";
      :semi_major_axis = 6377563.396; // double
      :semi_minor_axis = 6356256.91; // double
      :inverse_flattening = 299.3249646; // double
      :latitude_of_projection_origin = 49.0; // double
      :longitude_of_projection_origin = -2.0; // double
      :false_easting = 400000.0; // double
      :false_northing = -100000.0; // double
      :scale_factor_at_projection_origin = 0.9996012717; // double
      :_CoordinateTransformType = "Projection";
}

--
Dr Jon Blower
Technical Director, Reading e-Science Centre
Environmental Systems Science Centre
University of Reading, UK
Tel: +44 (0)118 378 5213
http://www.resc.reading.ac.uk


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• References:
  • [netcdf-java] Data in British National Grid coordinates
    • From: Jon Blower