Web Service Access and Display of USGS Oceanographic Time-Series Data Using the NOAA Earth Research Division's Data Access Program (ERDDAP)

The sediment transport group of the U.S. Geologic Survey Coastal Marine Geology Program (USGS CMGP) maintains an archive of more than 4400 NetCDF files collected over the last 30 years (Montgomery et al, 2007). The conventions used in these NetCDF files were determined long before the emerging standard Climate and Forecast (CF) conventions for NetCDF, and web access has been traditionally been limited to simple downloading of the NetCDF files. To take advantage of a growing suite of software that works with CF-compliant data, A combination of NcML and the THREDDS Data Server were used to allow web services access of CF compliant data via the OGC WCS service and OPeNDAP. The primary users of these coastal oceanographic measurements are modelers who are facile with netCDF files and URL references. Other users, however, may prefer to obtain the data in another format or perhaps just plot a variable. To assist both groups of users, we have evaluated NOAA's Earth Research Division's Data Access Program (ERDDAP) as a potential method of providing a more flexible and powerful interface to the data. This versatile program is able to access data from a variety of web services, including OPeNDAP, and then deliver the data using web services in a very wide variety of formats, from common image formats such as PNG and JPG (pictures of plots), to NetCDF, Matlab, text and spreadsheet formats. Installation and configuration of ERDDAP was straightforward. The software written in Java, and delivered as a War file that runs on a standard Tomcat server. Configuration of the user interface and the dataset list is controlled by XML files. The documentation is well written and much of the XML generation is handled by the supplied autogen function that reads a netCDF file and generates XML based on the file attributes. We are working on a Matlab program that will completely automate the process by interrogating our data holdings and producing the completely formed XML. Our initial assessment is that the ERDDAP server does indeed enable a more versatile way for users to interact with our data. Allowing users to select specific variables, time ranges and plot or data formats is a huge improvement. References Montgomery, E., Martini, M., Lightsom, F.L., and Butman, B., 2008, Documentation of the U.S. Geological Survey Oceanographic Time Series Measurement Database: U.S. Geological Survey Open-File Report 2007- 1194 (http://woodshole.er.usgs.gov/pubs/of2007-1194/)

enviro.er.usgs.gov/erddap