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UnidataTHREDDS Data Server

Overview

The THREDDS Data Server (TDS) is a web server that provides metadata and data access for scientific datasets, using OPeNDAP, OGC WMS and WCS, HTTP, and other remote data access protocols. The TDS is developed and supported by Unidata, a division of the University Corporation for Atmospheric Research (UCAR), and is sponsored by the National Science Foundation.

Some of the technology in the TDS:

  1. THREDDS Dataset Inventory Catalogs are used to provide virtual directories of available data and their associated metadata. These catalogs can be generated dynamically or statically.
  2. The Netcdf-Java/CDM library reads NetCDF, OpenDAP, and HDF5 datasets, as well as other binary formats such as GRIB and NEXRAD into a Common Data Model (CDM), essentially an (extended) netCDF view of the data. Datasets that can be read through the Netcdf-Java library are called CDM datasets.
  3. TDS can use the NetCDF Markup Language (NcML) to modify and create virtual aggregations of CDM datasets.
  4. An integrated server provides OPeNDAP access to any CDM dataset. OPeNDAP is a widely used, subsetting data access method extending the HTTP protocol.
  5. An integrated server provides bulk file access through the HTTP protocol.
  6. An integrated server provides data access through the OpenGIS Consortium (OGC) Web Coverage Service (WCS) protocol, for any "gridded" dataset whose coordinate system information is complete.
  7. An integrated server provides data access through the OpenGIS Consortium (OGC) Web Map Service (WMS) protocol, for any "gridded" dataset whose coordinate system information is complete. This software was developed by Jon Blower (University of Reading (UK) E-Science Center) as part of the ESSC Web Map Service for environmental data (aka Godiva2).

The THREDDS Data Server is implemented in 100% Java, and is contained in a single war file, which allows very easy installation into a servlet container such as the open-source Tomcat web server. Configuration is made as simple and as automatic as possible, and we have made the server as secure as possible. The library is freely available and the source code is released under the under the (MIT-style) netCDF library license.

Much of the realtime data available over the Unidata Internet Data Distribution (IDD) is available through a THREDDS Data Server hosted at Unidata on motherlode.ucar.edu. You are welcome to browse and access these meteorological datasets. If you need regular access to large amounts of data, please contact support-idd@unidata.ucar.edu.

System Requirements

Downloads

TDS version 4.0 is the stable release.

TDS 4.0 has many bug fixes and improvements "under the covers" that are not in the 3.17 release. Besides using the netcdf-java 4.0 library, the main new feature is the addition of an OGC WMS service, thanks to our collaborators Jon Blower (Univ. Reading UK) and Pauline Mak (Australian Research Collaboration Service) who did the hard work.

TDS version 4.1 is the development (alpha) release.

TDS version 3.17 is the previous stable release. It requires Java 1.5+. It is no longer being improved, and only critical bugs are being fixed.

Documentation

Experimental TDS Services

THREDDS Catalogs

THREDDS Catalogs are logical directories of on-line data resources, encoded as XML documents, which provide a place for annotations and other metadata about the data resources to reside. This is how THREDDS-enabled data consumers find out what data is available from data providers.

THREDDS Catalogs were originally designed for clients to use to access remote data. They have been extended to allow the TDS to use them for its own configuration. In this mode they are called TDS Configuration Catalogs, or server-side Catalogs. They contain information needed only on the server, which is removed when the TDS sends the catalog to the client, called the client-side or client-view catalog.

The TDS dynamically generates THREDDS catalogs based on the TDS configuration catalogs. For more information:

For client-side catalogs, the current specifications are:

 

Other TDS Services

Show Remote Catalog as HTML

CDM Coordinate System Validator

The Common Data Model (CDM) coordinate system validator is no longer part of the TDS distribution. Instead it comes as a separate distribution.

 

Other ways to use TDS

 

This document is maintained by John Caron and was last updated Sep 2009
 
 
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