NetCDF

NetCDF

Introduction to the NetCDF

NetCDF (Network Common Data Form) is a set of software libraries and self-describing, machine-independent data formats that support the creation, access, and sharing of array-oriented scientific data. It supports a view of data as a collection of self-describing, network-transparent objects that can be accessed through a simple interface. "Self-describing" means that a file includes information defining the data it contains. "Network-transparent" means that a file is represented in a form that can be accessed by computers with different ways of storing integers, characters, and floating-point numbers. The physical representation of netCDF data is designed to be independent of the computer on which the data were written.

The project homepage is hosted by the Unidata program at the University Corporation for Atmospheric Research (UCAR). They are also the chief source of netCDF software, standards development, updates, etc. The format is an open standard.

 

Collections of named multidimensional variables can be randomly accessed, without knowing details of how the data are stored. Auxiliary information about the data, such as what units are used, can be stored with the data. Generic utilities and application programmes can be written that access arbitrary netCDF files and transform, combine, analyze, or display specified fields of the data. Using the netCDF interface may lead to improved accessibility of data and improved reusability of software for scientific data management, analysis, and display.

 

A netCDF file contains three basic components:

  • Dimensions: provide information on the size of the data variables
  • Variables: store the actual data, the dimensions give the relevant dimension information for the variables, and the attributes provide auxiliary information about the variables or the dataset itself. All components have both a name and an ID number by which they are identified. These components can be used together to capture the meaning of data and relations among data fields in an array-oriented dataset; and
  • Global attributes: provide information about the data set as an entity. These attributes provide information about the spatial and temporal coverage of the data, where the data came from, who produced the data, and what has been done to them.

 

Tools

A wide range of application software has been written which makes use of netCDF files. A selected number of applications, into which GTN-P netCDF data formats can be integrated, is listed below:

ncBrowse: a Java application that provides flexible, interactive graphical displays of data and attributes from a wide range of netCDF data file conventions.

HTML I Download

ArcGIS versions after 9.2: The Multidimensional Tools toolbox can be used to create raster layers, feature layers, and table views from netCDF data in ArcMap, or convert feature, raster, and table data to netCDF.

ArcGIS tutorial "An overview of netCDF data": HTML I PDF

QGIS: load a netCDF file into QGIS using the python plugin "NetCDF Browser

 

Standards and convention

The conventions for CF (Climate and Forecast) metadata are designed to promote the processing and sharing of files created with the netCDF Application Programmer Interface. The conventions define metadata that are included in the same file as the data (thus making the file "self-describing"), that provide a definitive description of what the data in each variable represents, and of the spatial and temporal properties of the data.

CMIP5 Coupled Model Intercomparison Project

CF conventions version 1.6 (2011): HTML I PDF

NetCDF Attribute Conventions for Dataset Discovery: Wiki

 

GTN-P NetCDF Components

Dimensions:

Variables:

Global attributes:

Groups/types

Table GTN-P variables (in progress)

 

GTN-P NetCDF

In progress.

 

 

 

ISSN 2410-2385
Key title: GTN-P database