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Global Attributes

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John Kerfoot edited this page Mar 30, 2023 · 23 revisions

Wiki ▸ NetCDF Format Specification ▸ Global Attributes

The following is the list of global attributes required and recommended in the NetCDF specification. The goal of the NetCDF specification is to align with and adhere to the following conventions where possible:

Where applicable, the specfication relies on the of use controlled vocabularies to standardize attribute values. This standardization allows cataloging services to harvest data set metadata, which improves data set discovery and archiving:

Descriptions of required and recommended global attributes are found below.

Global Attributes

acknowledgment

Acknowledgement of funding agencies and sources used to produce the data

  • Example: "Funding provided by NOAA"
  • Role: required
  • Conventions/References:

comment

Additional information about the deployment not captured elsewhere. Typically includes deployment information including, but not limited to the deployment team, shoreside support, deploying boat, marine, etc.

  • Example: "Glider deployed by Bill Graham aboard the R/V Furthr out of San Francisco, CA. Shoreline support provided by Dick Latvala"
  • Role: required
  • Conventions/References:

Conventions

Comma separated list of conventions followed in creation of the file.

contributor_name

First and last names of all persons contributing the production of the data set. Multiple contributor names are separated by commas

  • Example: "Jerry Garcia,Bob Weir,Phil Lesh,Mickey Hart,Bill Kreutzmann,Keith Godchaux,Ron McKernan,Dick Latvala"
  • Role: required
  • Conventions/References:

contributor_role

The roles of all individuals or institutions that contributed to the creation of the data set, including glider preparation, deployment, shoreside support, data processing, etc. Multiple contributors are separated by commas. We recommend using the contributor roles provided in the NERC Vocabulary Server Contributor Roles G04 Collection as this controlled vocabulary provides standardized contributor roles.

  • Example: "principalInvestigator,collaborator,collaborator,collaborator,collaborator,collaborator,processor"
  • Role: required
  • Conventions/References: NERC contributor roles

contributor_role_vocabulary

URL for the vocabulary used to describe contributor_role. Multiple vocabularies are separated by commas.

creator_email

Email address(es) of the person or institution that collected the data. Multiple email addresses are separated by commas.

creator_institution

Institution(s) responsible for the collection and processing of the data. Multiple institutions are separated by commas. Current approved institution names can be found in the NCEI/GDAC Approved Institutions Authority Table. You may request adding a new/missing institution by Contacting the Glider DAC administration team.

creator_institution_url

URL of the institution responsible for the collection and processing of the data. Multiple URLs are separated by commas.

creator_name

Name(s) of the individuals responsible for the collection and processing of the data. Multiple names are separated by commas.

date_created

ISO-8601 formatted date and time at which the file was created.

date_issued

ISO-8601 formatted date and time at which the file was issued

date_modified

ISO-8601 formatted date and time at which the file was modified.

  • Example: "1977-05-09T08:00:00UTC"
  • Role: recommended if applicable
  • Conventions/References: ISO-8601 dates/times|

geospatial_bounds

Describes the data's 2D or 3D geospatial extent in OGC's Well-Known Text (WKT) Geometry format. The meaning and order of values for each point's coordinates depends on the coordinate reference system (CRS). The ACDD default is 2D geometry in the EPSG:4326 coordinate reference system. The default may be overridden with geospatial_bounds_crs and geospatial_bounds_vertical_crs. EPSG:4326 coordinate values are latitude (decimal degrees_north) and longitude (decimal degrees_east), in that order. Longitude values in the default case are limited to the [-180, 180) range.

geospatial_bounds_crs

Coordinate reference system for the geospatial_bound.

geospatial_bounds_vertical_crs

Coordinate reference system for the geospatial_vertical* attributes.

geospatial_lat_max

String containing the northernmost latitude of the profile.

  • Example: "39.44806115541661"
  • Role: required

geospatial_lat_min

String containing the southernmost latitude of the profile.

  • Example: "38.053496217125875"
  • Role: required

geospatial_lat_resolution

  • Example: "0.00001 degree"
  • Role: required

geospatial_lat_units

Latitude units.

  • Example: "degrees_north"
  • Role: required

geospatial_lon_max

String containing the easternmost longitude of the profile.

  • Example: "-73.04047803782304"
  • Role: required

geospatial_lon_min

String containing the westernmost longitude of the profile.

  • Example: "-74.76908104289834"
  • Role: required

geospatial_lon_resolution

Approximate longitude resolution.

  • Example: "0.00001 degree"
  • Role: required

geospatial_lon_units

Longitude units.

  • Example: "degrees_east"
  • Role: required

geospatial_vertical_max

Maximum depth of the profile.

  • Example: "97.8563"
  • Role: required

geospatial_vertical_min

Minimum depth of the profile.

  • Example: "0.01984897"
  • Role: required

geospatial_vertical_positive

Direction of increasing positive depth.

  • Example: "down"
  • Role: required

geospatial_vertical_resolution

Approximate resolution of the profiled depth measurements.

  • Example: "1"
  • Role: required

geospatial_vertical_units

Profile depth units

  • Example: "m"
  • Role: required

gts_ingest

Specifies whether the data is intended to be harvested by NDBC for release on the Global Telecommuncation System. Data released to the GTS are available for assimilation into local, regional and global ocean models to increase the accuracy of the forecasts and hindcast validation. In order for NDBC to harvest the dataset, this attribute must have a value of "True". If not included, the Glider DAC will automatically set this attribute to "True", indicating that the data is available for GTS release.

history

A string containing the processing and modification history for the data set. Each entry should begin with the ISO 8601:2004 Extended Date/Time Format (EDTF) and the name and command line parameters of the program used to create or change the data and/or other information about the change.

  • Example: “1977-05-08T20:00:00Z: Raw data processed to NetCDF with /bin/writeIoosNc.py
    1977-05-10T00:00:00Z: conductivity corrected for thermal lag with /bin/correct_thermal_lag.py”
  • Role: required
  • Conventions/References: CF Conventions

id

A unique identifier for data set. We recommend using the trajectory variable string name, which must have the following format:

  glider-YYYYmmddTHHMM-mode

Where glider is the name of the glider and YYYYmmddTHHMM is the deployment date/time and the mode is either "rt" or "delayed". The combination of the naming_authority and the id should be globally unique, but the id can be globally unique by itself also. IDs can be URLs, URNs, DOIs, meaningful text strings, a local key, or any other unique string of characters. The id should not include blanks.

institution

Institution(s) responsible for the collection and processing of the data. Multiple institutions are separated by commas. Current approved institution names can be found in the NCEI/GDAC Approved Institutions Authority Table. You may request adding a new/missing institution by Contacting the Glider DAC administration team.

ioos_regional_association

Acronym or full name of the IOOS regional association under which the deployment was funded, if applicable. This attribute may be omitted if the deployments is not IOOS funded.

  • Example: "MARACOOS" or "Mid-Atlantic Regional Association of Coastal Ocean Observing Systems"
  • Role: optional
  • Conventions/References: IOOS Regional Associations

keywords

A comma separated list of keywords in a keyword vocabulary collection. We do not require a specific keyword_vocabulary, but do suggest using one of the vocabularies contained in the Conventions/References. If no keywords are specified, the DAC will attempt to add pertinent keywords, but we cannot guarantee the accuracy or inclusion of all relevant keywords.

  • Example: “AUVS > Autonomous Underwater Vehicles, Oceans > Ocean Pressure > Water Pressure, Oceans > Ocean Temperature > Water Temperature, Oceans > Salinity/Density > Conductivity, Oceans > Salinity/Density > Density, Oceans > Salinity/Density > Salinity”
  • Role: required
  • Conventions/References: GCMD Keywords, NERC Vocabulary Service

keywords_vocabulary

The unique name or identifier of the vocabulary from which keywords are taken. If more than one keyword vocabulary is used, each may be presented with a prefix and a following comma, so that keywords may optionally be prefixed with the controlled vocabulary key. If no keywords are specified, the DAC will attempt to add pertinent keywords, but we cannot guarantee the accuracy or inclusion of all relevant keywords.

license

Description of the restrictions to data access, distribution and citation.

  • Example: "This data may be redistributed and used without restriction. Data provided as is with no expressed or implied assurance of quality assurance or quality control."
  • Role: required
  • Conventions/References: ACDD Conventions, IOOS Metadata Profile

mode

Identifies the data set as realtime ("rt") or delayed ("delayed"). Real-time data sets are typically decimated, lower resolution as compared to a delayed mode data set which is undecimated and high resolution. If omitted, the mode is set by the type of the data set specified on the data set registration page.

  • Example: "rt"
  • Role: required

naming_authority

The organization that provides the id for the dataset. The combination of the naming_authority and the id should be a globally unique identifier for the dataset. A reverse-DNS naming is recommended; URIs are also acceptable.

platform_type

Glider make and model.

processing_level

Description of the processing and quality control level of the data.

  • Example: "Level 0 data extracted from raw Slocum glider data files with QARTOD quality control algorithms applied."
  • Role: required
  • Conventions/References: ACDD Conventions

project

The name of the project(s) principally responsible for originating this data. Multiple projects are separated by commas.

  • Example: "LTER,CONVERGE"
  • Role: required
  • Conventions/References: ACDD Conventions

publisher_email

Email address of the publisher of the data. Multiple values are separated by commas. Individuals or group email addresses are allowed.

  • Role: required

publisher_name

Name of the publisher of the data. Multiple values are separated by commas. Individual or group names are allowed.

  • Role: required

publisher_url

A URL for the publisher of the data.

  • Role: **recommended, if available. Multiple values are separated by commas.

references

Published or web-based references that describe the data or methods used to produce it. Recommend URIs (such as a URLs, DOIs or Accession Records) for papers, references or archived records. Multiple references are be separated by commas.

sea_name

The names of the water body(s) in which the data were collected.

sea_name_vocabulary

URL of the vocabulary containing the sea_name

source

The input data sources regardless of the method of production method used.

  • Example: “Observational data from a profiling glider.”
  • Role: required
  • Conventions/References:

standard_name_vocabulary

Version of CF standard names used for variables. The vocabulary can be named or contain a url. If a variables does not have an existing standard name in the CF-managed list, the variable should not include a standard_name attribute. In these cases, a standard name can be proposed to the CF community for consideration.

summary

Provide a useful summary or abstract for the data in the file. This summary is used as the primary piece of information describing the data set for discovery and archiving purposes. As such, careful thought should be put into constructing the summary. The summary should contain the goals of the project, the planned track of the glider and the parameters measured and contained in the data set.

  • Example: “Slocum glider dataset gathered as part of the TEMPESTS (The Experiment to Measure and Predict East coast STorm Strength), funded by NOAA through CINAR (Cooperative Institute for the North Atlantic Region). The glider will be deployed in the coastal waters of New Jersey and perform onshore to offshore transects from the shelf across the shelf slope. This dataset contains physical oceanographic measurements of temperature, conductivity, salinity, density and estimates of depth-average currents.”

The following addendum is added to this attribute prior to archiving by NCEI:

“Addendum: The Integrated Ocean Observing System’s National Glider Data Assembly Center receives sets of individual NetCDF files comprising an individual glider deployment from data operators and providers around the world. These files are checked for compliance and then aggregated into a single data set representing the entire deployment and made available via ERRDAP and THREDDS end points, making the data sets available to the public. Currently, the data sets provide measurements of physical oceanographic properties (temperature, salinity, conductivity and density). Future plans, currently under development, include providing access to biological and chemical properties. Once the deployment has been completed, as specified by the glider operator or data provider, the data set is marked for archiving, at which point it is added to the National Centers for Environmental Information (NCEI, formerly NODC) data archive to create a permanent archive of the data set.”

time_coverage_duration

Duration/length of the profile specified in the ISO 8601:2004 duration format

time_coverage_end

ISO-8601 formatted timestamp specifying the end time of the profile.

time_coverage_resolution

Describes the targeted or approximate time period between each measurement in the profile specified in the ISO 8601:2004 duration format.

time_coverage_start

ISO-8601 formatted timestamp specifying the start time of the profile.

title

Title of the data set. We recommend using the same value as that used for the id attribute.

wmo_platform_code

Important Update: for previous versions of the Glider DAC NetCDF specification, this attribute was previously called wmo_id. Please update your processing code to change the attribute name.

The unique WMO ID code for the glider platform, specified as a string. This code must be requested for the specific platform and this code must only be used to identify the specific platform for which it was requested. Inclusion of a value for this attribute, combined with gts_ingest, enables the harvest and distribution of profiles from this data set to GTS. See the IOOS Metadata Profile documentation on GTS distribution for more information.

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