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Lowered Instrument DataContents |
Background
Measurements such as those made with in-situ instruments lowered from ships (CTD, bottles, XBT, etc.) may require a multi-step process to get the data distributed in real-time. The JCOMM Ship Observation Team (SOT) coordinates activities for ships participating in the Ship Of Opportunity Programme (SOOP ) There is much useful information at the SOOP web site even though the SOOP does not cover all platforms collecting data of this type. Questions can also be directed to the SOT Technical Co-ordinator at JCOMMOPS (see “Contacts” in right hand menu).
A description of the programme is available in an OceanObs'09 Community White paper.
Step 1: Getting platform identifiers
In order to report data on the GTS, the ship must use an identifier called a call sign. This is assigned to a ship by each country with due notification provided to the International Telecommunication Union (ITU). Each country has a member and this information is available from the ITU web site. They can help if you need to set the ship’s identification. Alternatively, and a more straightforward route, is to consult the SOT Coordinator.
Step 2: Getting data ashore
The data gathered on board the platform needs to be sent ashore. The ship can use the facilities promoted by the SOOP. To do so, contact either the SOT Chair or SOT Technical Coordinator.
Alternatively, countries may choose to get data ashore through other methods. For example,
data collected from research vessels will sometimes send data ashore through email. Alternatively, for cruises of short duration (shorter than the 30 day cut off for ocean data on the GTS), the cruise operator may bring the data back to port before any preparation for dissemination occurs. Contact your national co-ordinator for ocean data management or IODE (select “contact us” in the left hand menu) for advice or assistance.
Step 3: Formating data
After the data come ashore, they must be converted to the appropriate character code form (usually BATHY or TESAC) or into BUFR. If your country already has systems in place for this, your only task is to contact the people operating them. To identify them, it is simplest to contact the SOT technical Coordinator, or the SOOP Chair.
Step 4: Assistance in formatting data
If there are no systems in place in your country, then it may be that there is some international system already in place that can assist you in this task. For ocean profiles, you should consult the Global Temperature and Salinity Profile Project (GTSPP); they may be able to direct you to an organization that can assist.
If there is no existing organization that can help you, then you will need to take steps to convert the data into appropriate data formats for the GTS. These are generally described in the document “Formats for Real-time Data Exchange”. This document also describes how to get the data to the GTS.
Step 5: Quality Control
Data providers are encouraged to examine the data they collect and to remove the most egregious errors that are present. However, it is encouraged to be cautious in doing this since outliers may be real and to miss these will skew our perception of what is happening in the ocean. Users of GTS data are aware that very detailed quality control cannot take place before the data are distributed in real-time and they accept that they will need to carry out quality control procedures on the data that are distributed.
The Argo program has defined a minimum set of automated procedures that have been agreed to be carried out before data from profiling floats are distributed in real-time. These procedures are described in the Argo Quality Control Manual.
The GTSPP has published a quality control manual as well that describes an extensive set of tests that are applied after the data are distributed. A number of these can be automated and used to assess the quality of the data.
The BATHY and TESAC code forms have no capability to carry quality control flags so it is impossible for a data provider to describe what has been done to the data if they are distributed in these formats. The BUFR format does allow for reporting quality control flags, and if BUFR is used for distribution, data providers are strongly encouraged to use the facility.
If quality control is carried out on the data before distribution, it is vital that a very precise description of the tests are provided in easily accessible documentation. This can be available on an organization website, or provided to IODE as a central repository of such information.
An older document, Manuals and Guides #3, describes procedures for quality control that may also be of interest.
Additional Resources
GTSPP OceanObs'09 Community White Paper: http://www.oceanobs09.net/proceedings/cwp/cwp86/index.php
International Telecommunication Union: http://www.itu.int/
SOT: http://www.jcommops.org/sot/
Subsections of this Article
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Information about this article
Short title: Real-time Exchange of Lowered Instrument Data
Description: Step-by-step instructions for getting such data on the GTS.
Expertise level: beginner
Author: bob.keeley
Approval status: approved
Approved by: bob.keeley
Last change: 2012-2-9
Subsection of: Exchanging Ocean Data in Real-time
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