CF-netCDF

From Federation of Earth Science Information Partners

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CF-netCDF Description: [[TermDesc:=CF-netCDF is the Climate and Forecast Metadata Convention for NetCDF Files. Names in NetCDF don't have any meaning associated in them, CF Conventions standardizes the semantic meaning of names, and physical dimensions. CF-netCDF files can be read with semantic meaning associated to the data.]]

Glossary Domain: WCS

Related Links

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[[Links:=CF Conventions Data Configuration for Cubes]]

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Term Details

NetCDF file format contains four kinds of information:

  • Global attributes
    • Simple name=value pairs
  • Dimensions
    • Only declares the length of the dimension
    • Contains no dimension data.
  • Variables
    • Array data with any number of dimensions.
    • Zero dimensions meaning scalar data.
  • Variable Attributes:
    • Simple name=value pairs associated to a variable.

While these are enough to describe any data, it's not easy to interpret what the data actually means. What is self-evident for humans is difficult for a computer program to reason. If you have a NetCDF viewer, it should be possible just open the file and display the data on a geographic map. But making a program that can automatically get the geographic dimensions from a NC file, is very difficult.

Conventions come to rescue. CF Standardizes many things:

  • Standard name: what is the measure data about
  • Units
  • How to tell, that a variable is one of the following:
    • Data Variable, containing real data.
    • Dimension Coordinate Variable, containing dimension coordinates.
    • Dimension Bounds Variable, containing lower and upper bounds of a dimension coordinate.
  • Projection

With this part standardized, your program can list the data variables for you and tell you exactly what you can filter by.

Links:

CF 1.0 - 1.5 contain conventions for cube data and 1.5 contains some station data.

Unofficial CF-1.5 contains point data encoding. Expired certificate, add security exception.

CF Conventions

NetCDF Conventions

Unidata NetCDF documentation

Creating NetCDF CF Files