sdfopen filename <template #timesteps>    (GrADS version 1.9* and earlier)
sdfopen filename                          (GrADS version 2.0* and later)

Opens a NetCDF or HDF-SDS format file that conforms to the COARDS conventions. The sdfopen command does not support the HDF5 format, but is does support netcdf4. The template and#timesteps arguments were eliminated starting with version 2.0. The arguments and options are as follows:

Usage Notes

  1. The template option with sdfopen was removed in version 2.0. If you want to aggregate multiple files together use the xdfopen command with the 'options template" keyword and a complete TDEF entry.
  2. Here's a brief summary of the metadata that sdfopen is looking for when it tries to open a self-describing file. As it goes through the list of dimension variables in the file, it checks each one for attributes named "units", "axis", and "grads_dim". Acceptable values for these attributes and the GrADS dimension the coordinate variable maps to are outlined in this table:

    GrADS Dimension
    Acceptable Attribute Values
    units: degrees_east, degree_east, degrees_E, degree_E
    axis: x, X
    unit: degrees_north, degree_north, degrees_N, degree_N
    axis: y, Y
    Z (pressure)
    units: mb, millibar, hybrid_sigma_pressure
    Z (not pressure)
    units: sigma_level, degreesk, degrees_k, level, layer, layers
    axis: z, Z
    units: yyyymmddhhmmss, yymmddhh, or a Udunits-acceptable time unit
    axis: t, T
    grads_dim: e
    axis: e, E

  3. If the sdfopen command fails to open your self-describing file, try using the xdfopen command which requires a special descriptor file to supplement or override the metadata in the file, or use the open command with a complete descriptor file.


  1. If you had daily U-Wind data in two files, and, you could access them both as one GrADS data set by entering:

    sdfopen /data/ 730