The Marine Modeling and Analysis Programs (MMAP) branch of the Coast Survey Development Laboratory is implementing a Live Access Server (LAS) to offer web access to MMAP’s hydrodynamic model output. The Live Access Server (LAS) is a highly configurable Web server designed to display and download model data. It can present distributed data sets as a unified virtual database through the use of OPeNDAP/DODS networking. OPeNDAP/DODS is a data system intended to allow researchers transparent Internet access to oceanographic data—stored in any of several different file formats. In MMAP, Network Common Data Format (NetCDF) is chosen as the standard to store model outputs.

MMAP currently serves the NOS Gulf of Mexico (NGOM) model output data via the LAS.   Other model output datasets will be added later as the system is expanded. By accessing this URL in any web browser, users can easily request NGOM output files, subsets of output files, and aggregated data. This allows model output to be quickly and efficiently disseminated to a broad audience in numerous configurations. Users also can access metadata which describes the characteristics of the data set. The key point of LAS is that web users can easily visualize model output data with on-the fly graphics. Ferret is the visualization application used by MMAP LAS to create dynamically generated images of model data at the user’s request. The figure below demonstrates the capability of this approach.

The MMAP LAS serves data 24 hours a day, 7 days a week, to web users. Users locate the desired dataset by navigating the hierarchical data structure. After selecting the desired variable, users will see an initial image of model domain, and be able to select any region of the model by using the moveable resize box. The products can be saved as either images or NetCDF files. Users can also grab metadata information by clicking on the OPeNDAP link on the right top of page. Without LAS, model outputs are usually distributed in separate files produced by sequential model runs. LAS offers aggregated data as a whole, so that users don’t need to download separate files one by one. Currently, aggregation is completed in real-time by the Ferret default aggregation server, which is not very efficient for large size files. In the near future, a Thematic Realtime Environmental Distributed Data Services (THREDDS) server will be enabled to aggregate data, which will allow users to make a single query to get large volumes of aggregated data in a flash.