Real Time File Description

Introduction

netCDF file

CF 1.6 Discrete Sampling Geometry (Trajectory)

Attribute Conventions for Dataset Discovery (link)

Main objective is aggregation of these files for web service distribution via THREDDS Data Server.

Global Attributes

The Global Attributes that are included in the real time glider files are listed and defined below. These attributes derive from several sources as indicated in the square brackets next to the terms. More information on these sources can be found at the following locations.

• CF1.6 Section 2.6 of the current (v1.6) Climate and Forecast conventions
• ACDD Attribute Conventions for Dataset Discovery Home page and Current Standard
• NODC Guidance from NOAA's National Oceanographic Data Center on netCDF templates to promote good stewardship and archiving. NODC Templates and global attribute suggestions. In addition to listing useful attributes NODC provides a style guide to help in populating the global attributes with useful and clear information.
• IMOS/ANFOG IMOS Data Management manual version 3.1
• IOOS Internal discussion within the IOOS Glider Data Team.

acknowledgement [ACDD]

A place to acknowledge various type of support for the project that produced this data.

cdm_data_type [ACDD]

The THREDDS data type appropriate for this dataset.

comment [CF/ACDD]

Miscellaneous information about the data.

contributor_name

A comma separated list with the names of any individuals or institutions that contributed to the creation of this data.

contributor_role

A comma separated list with the roles assumed by the individuals or institutions that are referenced in contributor_name.

creator_email

Email address for the person principally responsible for creating the digital data set.

creator_name

Name of the person principally responsible for creating the digital data set. The data creator's name, URL, and email. The "institution" attribute will be used if the "creator_name" attribute does not exist.

creator_url

URL to a page with reference information describing creation of the data set.

date_created

The date on which the data was created. [Following ISO 8601](http://en.wikipedia.org/wiki/ISO_8601)

date_issued

The date on which this data was formally issued.

date_modified

The date on which this data was last modified.

featureType

The CF 1.6 DSG featureType used to encode the data in the data set (e.g trajectory)

file_version [IOOS]

The version of the IOOS RT Glider template. (e.g. IOOS_Glider_NetCDF_Trajectory_Template_v0.1)

geospatial_bounds

Describes geospatial extent using any of the geometric objects (2D or 3D) supported by the Well-Known Text (WKT) format.

geospatial_lat_max

The values of geospatial_lon_min and geospatial_lon_max reflect the actual longitude data values. Cases where geospatial_lon_min is greater than geospatial_lon_max indicate the bounding box extends from geospatial_lon_max, through the longitude range discontinuity meridian (either the antimeridian or Prime Meridian), to geospatial_lon_min.

geospatial_lat_min

Describes a simple latitude/longitude bounding box. geospatial_lat_min specifies the southernmost latitude; geospatial_lat_max specifies the northernmost latitude; geospatial_lon_min specifies the westernmost longitude; geospatial_lon_max specifies the easternmost longitude of the bounding box.

geospatial_lat_resolution

geospatial_lat_units

Further refinement of the geospatial bounding box can be provided by using these units and resolution attributes.

geospatial_lon_max

geospatial_lon_min

For a more detailed geospatial coverage, see the suggested geospatial attributes.

geospatial_lon_resolution

geospatial_lon_units

geospatial_vertical_max

geospatial_vertical_min

Describes a simple vertical bounding box. For a more detailed geospatial coverage, see the suggested geospatial attributes.

geospatial_vertical_positive

TODO: Better represented as a variable attribute for depth?

geospatial_vertical_resolution

geospatial_vertical_units

history [CF/ACDD]

Provides an audit trail for modifications to the original data. Well-behaved generic netCDF filters will automatically append their name and the parameters with which they were invoked to the global history attribute of an input netCDF file. We recommend that each line begin with a timestamp indicating the date and time of day that the program was executed.

id [ACDD]

An identifier for the data set, provided by and unique within its naming authority. 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 [CF/ACDD]

Specifies where the original data was produced.

keywords

A comma separated list of key words and phrases.

keywords_vocabulary

If you are following a guideline for the words/phrases in your "keywords" attribute, put the name of that guideline here.

license

Describe the restrictions to data access and distribution.

metadata_conventions

TODO: Research this term.

metadata_link

URL that gives the location of more complete metadata than is available in the file. It may include, among other things, more detailed sensor metadata or a high level collection record. TODO: Check the ACDD docs. Capitalization?

naming_authority

TODO: Find def

processing_level

A textual description of the processing (or quality control) level of the data.

project

The scientific project that produced the data.

publisher_email

publisher_name

The data publisher's name, URL, and email. The publisher may be an individual or an institution.

publisher_url

references [CF]

Published or web-based references that describe the data or methods used to produce it.

sea_name [NODC]

Contains information on the large scale oceanographic name in which the glider is deployed.

source [CF]

The definition from [CF](http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#description-of-file-contents): The method of production of the original data. If it was model-generated, source should name the model and its version, as specifically as could be useful. If it is observational, source should characterize it (e.g., "surface observation" or "radiosonde"). Recommended usage: "Observational data form a profiling glider".

standard_name_vocabulary

The name of the controlled vocabulary from which variable standard names are taken. As of 05 July 2013 the most current version of the [CF controlled vocabulary](http://cf-pcmdi.llnl.gov/documents/cf-standard-names) list is v25. Recommended usage: CF v25

summary

A paragraph describing the dataset.

time_coverage_duration

time_coverage_end

time_coverage_resolution

time_coverage_start

Describes the temporal coverage of the data as a time range.

title [CF]

A succinct description of what is in the dataset.

File Naming Convention

The following list specifies the 4 file types which will be accepted by the IOOS National Glider Data Acquisition Center and the proposed naming conventions for each:

• glider-SN_yyyymmddTHHMMSS_rt0.nc: Real-time data with no QC. This is the minimum processing level accepted by the DAC and contains the raw data values with no operator provided quality control.
• glider-SN_yyyymmddTHHMMSS_rt1.nc: Real-time data with operator provided QC
• glider-SN_yyyymmddTHHMMSS_delayed0.nc: Delayed-mode data with no QC
• glider-SN_yyyymmddTHHMMSS_delayed1.nc: Delayed-mode data with operator provided QC

where

glider

Identifying name or type abbreviation for the glider

SN

vehicle serial number as provided by the manufacturer

yyyymmddTHHMMSS

http://en.wikipedia.org/wiki/ISO_8601 [ISO 8601](http://en.wikipedia.org/wiki/ISO_8601) formatted date representing the start time of the data acquisition

'rt' or 'delayed'

string specifying real-time (during deployment) or delayed mode (post-recovery) data acquisition

0 or 1

quality control level where 0 corresponds to none and 1 corresponds to some level of operator applied quality control

Ideally, the glider-SN_yyyymmddTHHMMSS_rt1.nc files will be provided by the individual operators during the deployment and the glider-SN_yyyymmddTHHMMSS_delayed1.nc files will be provided after the glider has been recovered and the full data set processed. It is expected that all files containing operator QC'd data will provide the appropriate VARIABLE_qc variables with corresponding attributes from the CF specification.

Axis/Dimension Definitions

Trajectory

Variable Description

Mandatory Variables

Dimensionless Container Variables

The NODC netCDF templates have introduced a convention that is very useful for encoding platform and instrument metadata in a modular way. Dimensionless container variables act as place-holders for platform and instrument metadata and are easily referenced from geophysical variables with variable attributes. For example, the following variable, platform, contains information describing the glider platform used to collect the measurements.

int platform
  platform:type = "spray"
  platform:wmo_id = "NNYYXX" ;
  platform:comment = "Spray Glider sp111" ;
  platform:id = "sp111" ;
  platform:long_name = "Spray Glider sp111" ;
  platform:instrument = "instrument_ctd" ;

Similarly, the following instrument container variable contains metadata for the CTD sensor that is mounted on the above "spray" glider platform.

int instrument_ctd
   instrument_ctd:comment = "Unpumped CTD with a nominal sampling rate of 1Hz." ;
   instrument_ctd:serial_number = -1 ;
   instrument_ctd:long_name = "Seabird SBD 41CP Conductivity, Temperature, Depth Sensor." ;
   instrument_ctd:platform = "platform"

Optional Variables

Discussion topic: Optional variables are acceptable to the DAC and will be passed through without further processing.

Codes and External References

QC Codes

Platform Types: The platfrom:type attribute is selected from the following controlled vocabulary.

1. slocum
2. spray
3. seaglider

Quality Control