An integral part of GCMD’s mission is the development and maintenance of GCMD keywords.
These keywords ensure that metadata are described in a consistent manner and allow for precise
searches of metadata records and subsequent retrieval of data and services. GCMD keywords are
also used in other applications within the broader scientific community. Given the wide adoption
of GCMD keywords within the broader community, it is critically important to document the
processes NASA employs to ensure keywords continue to be relevant to the user and provider
communities and evolve with their changing needs.
The GCMD keywords are organized into 12 sets, (including Earth science keywords, platforms,
instruments, data centers, locations, projects, services, and data resolution) described in Section
4. The term controlled refers to keywords that are predefined in a precise manner and
continually evaluated for their usefulness and logical consistency in relation to the other
keywords. Initiated over 20 years ago, these controlled GCMD keywords will be periodically
analyzed for relevancy and will continue to be refined and expanded in response to user needs
following the governance process defined in this document.
Unless otherwise stated, the terms GCMD keywords and keywords should be understood to mean
the controlled keywords that comprise the keyword vocabularies defined and maintained
specifically by GCMD.
A citation should be referenced when using GCMD keywords in scientific literature, websites,
software tools, etc. Citation guidance and text is available on the GCMD Keyword Forum.
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Description
NASA's Global Change Master Directory (GCMD) holds more than 34,000 Earth science data
set and service descriptions that cover subject areas within the Earth and environmental
sciences. The mission of GCMD is to help researchers, policy makers, and the public find and
access data and related services relevant to global change and Earth science research. Within this
mission, GCMD offers online tools for providers of data and services to facilitate its use by the
Earth science community. In addition, citation information to properly credit data set
contributions is offered, along with direct links to data and services.
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Initial created on
March 28, 2025.
For additional information, contact
Earth Data Team (support@earthdata.nasa.gov).
