OPeNDAP Servers Tutorials

OPeNDAP (DODS) allows users seamless access to remote data using various analysis and visualization packages such as Ferret, GrADS, and MATLAB. The user also can use user-friendly client tools such as Panoply, IDV, and EDC without the user having to write scripts. OPeNDAP stands for Open-source Project for a Network Data Access Protocol. It is a data transport medium that allows access and subseting of data across the internet.

Who should use OPeNDAP?

Anyone who uses an OPeNDAP enabled client tools to analyze data. An advantage of using OPeNDAP clients over web-based servers is that the user has more control of the data and the resulting graphics.

Why use OPeNDAP?

OPeNDAP saves time and storage space. Users no longer need to download entire datasets and convert them to a format that is compatible to their application.

Which OPeNDAP servers are used at the APDRC?

GrADS Data Server (GDS)

The GrADS Data Server (GDS, formerly known as GrADS-DODS Server) is a stable, secure data server that provides subsetting and analysis services across the internet. The GDS subsetting capability allows users to retrieve a specified temporal and/or spatial subdomain from a large dataset, eliminating the need to download everything simply to access a small relevant portion of a dataset.


Dapper is an OPeNDAP web server developed by the EPIC group at PMEL that provides networked access to in-situ and gridded data. With Dapper, OPeNDAP enabled clients now have remote access to millions of previously unavailable in-situ oceanographic or atmospheric observations.

THREDDS Data Server (TDS)

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.

How to use OPeNDAP?

The first step would be to determine the OPeNDAP URL of the dataset of interest. The APDRC utilizes four different OPeNDAP servers:

DODS Extentions - There are 3 files associated with each set of data:

  1. Information (info): contains detailed information about the data in a more readable format.
  2. Dataset Descriptor Structure (dds): contains a description of the structure of the data.
  3. Data Attribute Structure (das): contains information about the data such as the name of the variable, its unit, and its type.

The OPeNDAP URL is found in the Information (info) page.

After determining the OPeNDAP URL, users can access data by referring to their favorite client tool's tutorial.

For more information, visit the OPeNDAP website and DODS website