NetCDF

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== summary ==
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{{FormatInfo
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|formattype=electronic
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|subcat=Scientific Data formats
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|extensions={{ext|nc}}
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|mimetypes={{mimetype|application/netcdf}}
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|locfdd={{LoCFDD|fdd000330}}, {{LoCFDD|fdd000332}}, {{LoCFDD|fdd000339}}
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|pronom={{PRONOM|fmt/282}}, {{PRONOM|fmt/283}}
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}}
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== General description ==
  
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The Network Common Data Form (netCDF) is a long-lived set of file formats and associated APIs designed by UCAR for multi-dimensional datasets. (Though its name resembles that of CDF, and their original designs were similar, the two products have greatly diverged.) The various versions are widely used in environmental science, especially atmospheric and oceanographic research. Currently it has two main versions, netCDF-3 and netCDF-4, which are quite different in implementation, and moderately different in API. There are also "subversions" of netCDF-3, notably "netCDF Classic." Tool support for netCDF-3 continues to exceed that for netCDF-4; but the latter, based on HDF5, is generally considered technically superior, so its tool support is increasing rapidly.
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The Network Common Data Form (netCDF) is a long-lived set of file formats and associated APIs designed by UCAR for multi-dimensional datasets. (Though its name resembles that of [[Common Data Format|CDF]], and their original designs were similar, the two products have greatly diverged.) The various versions are widely used in environmental science, especially atmospheric and oceanographic research. Currently it has two main versions, netCDF-3 and netCDF-4, which are quite different in implementation, and moderately different in API. There are also variants of netCDF-3, notably "netCDF Classic." Tool support for netCDF-3 continues to exceed that for netCDF-4; but the latter, based on [[HDF5]], is generally considered technically superior, so its tool support is increasing rapidly.
  
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Notable features of netCDF include
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Notable features of netCDF include:
  
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* incorporation of metadata. netCDF is said to be "self-describing," in that the file format provides for a header describing the structure of the data. In practice, the utility of its metadata depends on the extent to which the data author provides and maintains it.
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* incorporation of metadata. NetCDF is said to be "self-describing," in that the file format provides for a header describing the structure of the data. In practice, the utility of its metadata depends on the extent to which the data author provides and maintains it.
 
* platform independence via API: provided the user manipulates netCDF files via supported APIs (which are numerous), the user can effectively ignore issues such as endianness.
 
* platform independence via API: provided the user manipulates netCDF files via supported APIs (which are numerous), the user can effectively ignore issues such as endianness.
 
* backward compatibility. Software and API capable of manipulating netCDF-4 is also capable of manipulating netCDF-3, though of course advanced features of the later version are not accessible to files written for the earlier version.
 
* backward compatibility. Software and API capable of manipulating netCDF-4 is also capable of manipulating netCDF-3, though of course advanced features of the later version are not accessible to files written for the earlier version.
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According to the [https://docs.unidata.ucar.edu/netcdf-c/current/faq.html#formatsdatamodelssoftwarereleases FAQ], there are five main versions of netCDF:
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*    the netCDF-3 classic format (CDF-1)
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*    the 64-bit offset format (CDF-2)
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*    the 64-bit data format (CDF-5)
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*    the netCDF-4 format
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*    the netCDF-4 classic model format
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Any of the first three may be referred to as netCDF-3.
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NetCDF is described on the [https://www.unidata.ucar.edu/software/netcdf/ Unidata pages] of the UCAR web site. A short document [http://www.esdswg.org/spg/rfc/esds-rfc-011/ESDS-RFC-011v1.00.pdf describing early versions] has been accepted as a standard by NASA.
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NetCDF-4 based on [[HDF5]] has been endorsed as a standard by NASA's Earth Observing System Data and Information System (EOSDIS).  See [http://earthdata.nasa.gov/our-community/esdswg/standards-process-spg/rfc  Endorsed set of EOSDIS approved standards.]
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== Other information ==
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The format is referenced in the Wikipedia [https://en.wikipedia.org/wiki/NetCDF page on netCDF).
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NetCDF claims full backwards compatibility.
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Software and information are available under a [https://github.com/Unidata/netcdf-c/blob/main/COPYRIGHT permissive BSD 3-Clause "New" or "Revised" License].  Commercial and private purposes are both permitted.
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== Software ==
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There is a wide range of software available to create and process netCDF files. The Wikipedia article mentioned above has a starter list.
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== Sample files ==
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Sample netCDF files are available on the [https://archive.unidata.ucar.edu/software/netcdf/examples/files.html Unidata web site].
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== Identification ==
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Magic numbers:
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*    NetCDF-3 classic format: CDF\001
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*    64-bit offset format: CDF\002
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*    64-bit data format: CDF\005
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*    NetCDF-4 formats, HDF5-based: \211HDF\r\n\032\n (Same as [[HDF5]])
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The preferred file extension for all NetCDF variants is .nc (originally .cdf).  An alternate .ncf is less common.
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The MIME Type is application/netcdf or application/x-netcdf.
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== References ==
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* The User's Guide is: Rew, R. K., G. P. Davis, S. Emmerson, and H. Davies, NetCDF User's Guide for C, An Interface for Data Access, Version 3, April 1997.
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* [https://docs.unidata.ucar.edu/netcdf-c/current/faq.html#formatsdatamodelssoftwarereleases NetCDF FAQ 2026]
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* [https://deepblue.lib.umich.edu/bitstream/handle/2027.42/145724/Public-Data-CurationFormat%20Profile-netCDF.pdf Data Curation Format Profile: netCDF] (Research Data Services, University of Michigan Library)
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[[Category:HDF based file formats]]

Latest revision as of 23:55, 12 June 2026

File Format
Name NetCDF
Ontology
Extension(s) .nc
MIME Type(s) application/netcdf
LoCFDD fdd000330, fdd000332, fdd000339
PRONOM fmt/282, fmt/283

Contents

[edit] General description

The Network Common Data Form (netCDF) is a long-lived set of file formats and associated APIs designed by UCAR for multi-dimensional datasets. (Though its name resembles that of CDF, and their original designs were similar, the two products have greatly diverged.) The various versions are widely used in environmental science, especially atmospheric and oceanographic research. Currently it has two main versions, netCDF-3 and netCDF-4, which are quite different in implementation, and moderately different in API. There are also variants of netCDF-3, notably "netCDF Classic." Tool support for netCDF-3 continues to exceed that for netCDF-4; but the latter, based on HDF5, is generally considered technically superior, so its tool support is increasing rapidly.

Notable features of netCDF include:

  • incorporation of metadata. NetCDF is said to be "self-describing," in that the file format provides for a header describing the structure of the data. In practice, the utility of its metadata depends on the extent to which the data author provides and maintains it.
  • platform independence via API: provided the user manipulates netCDF files via supported APIs (which are numerous), the user can effectively ignore issues such as endianness.
  • backward compatibility. Software and API capable of manipulating netCDF-4 is also capable of manipulating netCDF-3, though of course advanced features of the later version are not accessible to files written for the earlier version.

According to the FAQ, there are five main versions of netCDF:

  • the netCDF-3 classic format (CDF-1)
  • the 64-bit offset format (CDF-2)
  • the 64-bit data format (CDF-5)
  • the netCDF-4 format
  • the netCDF-4 classic model format

Any of the first three may be referred to as netCDF-3.

NetCDF is described on the Unidata pages of the UCAR web site. A short document describing early versions has been accepted as a standard by NASA.

NetCDF-4 based on HDF5 has been endorsed as a standard by NASA's Earth Observing System Data and Information System (EOSDIS). See Endorsed set of EOSDIS approved standards.

[edit] Other information

The format is referenced in the Wikipedia [https://en.wikipedia.org/wiki/NetCDF page on netCDF).

NetCDF claims full backwards compatibility.

Software and information are available under a permissive BSD 3-Clause "New" or "Revised" License. Commercial and private purposes are both permitted.

[edit] Software

There is a wide range of software available to create and process netCDF files. The Wikipedia article mentioned above has a starter list.

[edit] Sample files

Sample netCDF files are available on the Unidata web site.

[edit] Identification

Magic numbers:

  • NetCDF-3 classic format: CDF\001
  • 64-bit offset format: CDF\002
  • 64-bit data format: CDF\005
  • NetCDF-4 formats, HDF5-based: \211HDF\r\n\032\n (Same as HDF5)

The preferred file extension for all NetCDF variants is .nc (originally .cdf). An alternate .ncf is less common.

The MIME Type is application/netcdf or application/x-netcdf.

[edit] References

  • The User's Guide is: Rew, R. K., G. P. Davis, S. Emmerson, and H. Davies, NetCDF User's Guide for C, An Interface for Data Access, Version 3, April 1997.
  • NetCDF FAQ 2026
  • Data Curation Format Profile: netCDF (Research Data Services, University of Michigan Library)
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