Opendap

What the Opendap can do?

Opendap handles transport, translation and subsetting of data. Opendap allows you to access remote data over the internet:

  • using familiar data analysis and visualization packages like Matlab, Ferret, IDL,... as if the data were on your computer
  • without worrying about data storage formats, translating them on-the-flight (including in ascii), if necessary
  • accessing only the data of interest (extracting geographical area, time series...).

How to use the Opendap ?

Since August 2010, an authentication is required to access all the Ssalto/Duacs data (see Upgrade and modifications on the Opendap and Extraction Tool, 2010/08/26). If you are not registered and want to access those services (NB. for scientifc uses only), we request you to fill in the online form. Then, an individual hostname and a password will be sent.

For example, to use Ssalto/Duacs merged near-real time sea level anomaly data (merged NRT-MSLA) with Ferret software :

  • launch Ferret
  • type : use "http://USERNAME:PASSWORD@tds.aviso.altimetry.fr/thredds/dods/dataset-xxx..."  (see Aviso Opendap for another data http addresses)
  • then "show data" shows the file characteristics.

Sea Level Anomalies are in "sla". This grid includes all available msla_merged_h data from the beginning. "show grid sla" returns number of points, beginning and end value, in longitude, latitude and time. sla can be used as a local data source; network access are completely transparents, and concern only selected data.
For more information, look at an exemple of command lines and of maps in a Lively Data: Direct access to the data behind the LAS

You thus can plot a map, a longitude-time diagram, etc. What can be done with Ferret is also possible with other "client" software like ncBrowse, IDL, Matlab... (see OpenDap website for the complete software list)

Have a look at Aviso Opendap products