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What is netCDF?

Unidata's Network Common Data Form (netCDF) is a set of software libraries and machine-independent data formats that support the creation, access, and sharing of array-oriented scientific data. It is also a community standard for sharing scientific data.
Data in netCDF format is:

  • Self-Describing. A netCDF file includes information about the data it contains.
  • Portable. A netCDF file can be accessed by computers with different ways of storing integers, characters, and floating-point numbers.
  • Scalable. Small subsets of large datasets in various formats may be accessed efficiently through netCDF interfaces, even from remote servers.
  • Appendable. Data may be appended to a properly structured netCDF file without copying the dataset or redefining its structure.
  • Sharable. One writer and multiple readers may simultaneously access the same netCDF file.
  • Archivable. Access to all earlier forms of netCDF data will be supported by current and future versions of the software.

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Description Improvement

NetCDFs are self describing, but the structure for descriptions are extremely flexible. We can improve these descriptions using the Attribute Conventions for Dataset Discovery (ACDD). Use of the conventions will support interoperability and understanding when we share our data with other THREDDS catalogs and translate to other standards, such as ISO.

Recommended Practices

  • Use ACDD Conventions for global attributes
    • e.g. “metadata_link” instead of “metadata_url”
  • Use CF convention names when available for each variable
    • :standard_name= “longitude";
  • Use ISO 8601 date formats
  • Start with NODC templates if applicable to your datatype

How to Evaluate

1. Create or save NcML file - below are some options.

  • Open NetCDF file in ToolsUI and save the NCML with .xml extension
  • Download NCML from NGDC Thredds server
  • Generate from the command line

2. Evaluate XML file with NcML Rubric - below are some options.

  • Transform in Oxygen Editor
  • Use Docucomp Record Services