Coastal and Marine Geoscience Data SystemSingle Point of Access for Digital Geophysical and Lidar Data of the USGS Coastal and Marine Geology Program
The Coastal and Marine Geoscience Data System (CMGDS) is now online and will eventually provide a single point of access to geophysical and lidar (light detection and ranging) data collected by the U.S. Geological Survey (USGS) Coastal and Marine Geology Program (CMGP). The CMGDS uses a “technology stack” or suite of open-source Web services and protocols to help users easily discover and access CMGP data. Initial efforts are focused on adding the most recent seismic-reflection, bathymetric, and lidar data to the system, which will eventually also include sidescan-sonar mosaics and gravity and magnetic data.
Users are helped to find data by various search methods, including interactive global map displays for data type or field activity; publication listings that can be sorted by data type, geographic area, data-access method, or date of acquisition; and a catalog of published metadata. (Metadata is information about the data, such as how, when, where, and by whom they were collected.) These methods can be accessed through tabs at the top of each Web page or from the body of the homepage, which provides more detail about each data-discovery or data-access method.
Where appropriate, access to data types will be provided via several methodologies: file download; the Open Geospatial Consortium (OGC)’s standard Web Map Service (WMS), Web Coverage Service (WCS), and Web Feature Service (WFS) (learn more at http://www.opengeospatial.org/standards/); THREDDS (Thematic Realtime Environmental Distributed Data Services); and GeoMapApp and Virtual Ocean (see related article on GeoMapApp and Virtual Ocean, this issue).
If the data are already posted online, the CMGDS will point to that source. Otherwise, the CMGDS provides data storage for direct data download. OGC Web services are provided via an open-source-software server called GeoServer, which allows users to view and integrate geospatial data via a wide variety of geographic-information-system (GIS) software. In addition, a THREDDS service is provided for NetCDF (Network Common Data Form, http://www.unidata.ucar.edu/software/netcdf/) access to some bathymetric datasets. Links are also provided for some NetCDF viewers, such as Integrated Data Viewer (IDV), NetCDP-Java Tools UI, and Godiva2.
What else is under the Web site’s hood? For the Global Map Search function, shapefiles are created and displayed for each data type collected for each field activity and are served up using OpenLayers interactive Web mapping software. Each shapefile is linked by a popup window to more information about the dataset, such as field-activity ID, data type, date collected, online publication, data-download location, and a link to more general information about the field activity. A similar display, called “Field Activity Map Search,” uses Google Maps to show the location of each field activity by CMGP Center, with field activity ID and data coverage revealed when the cursor is positioned over the marker. Clicking on the marker displays a popup window with information similar to that provided in the Global Map Search display. These easy-to-use GIS displays allow the user to search geospatially for CMGP data by data type.
The same shapefiles are also served via a WMS to allow use in other GIS software. The Data Publications function is controlled by a mySQL database, which generates the publication listings sorted by geographic location, data type, acquisition date, or data-delivery method. The GeoNetwork Metadata Search function uses the GeoNetwork open-source metadata-cataloging software to search and retrieve Federal Geographic Data Committee (FGDC) metadata previously uploaded from the publications. CMGDS OGC Web services are also harvested into this metadata catalog. (Web “harvesting” is the use of Web-crawling software to automatically copy and collect Internet content, such as Web-site pages, to create a more focused set of information.) GeoNetwork allows local searches of the metadata and also facilitates metadata harvesting by other metadata-cataloging systems, such as the new prototype Geoportal used by the Interagency Working Group for Ocean and Coastal Mapping (IWG-OCM) inventory project and, in the future, Data.gov.
Population of the CMGDS is an ongoing task. Initial efforts are focusing on seismic-reflection (single-channel and multichannel), bathymetric, sidescan-sonar, and lidar datasets.
Recent single-channel seismic and lidar datasets are nearly complete. Many older datasets will need to be published before inclusion. Frequently-asked-question (FAQ) pages and video demonstrations of services are being developed to aid in the use of this site. The site currently contains 148 single-channel seismic datasets, 20 multichannel seismic datasets, 67 lidar datasets, 70 bathymetric datasets, 42 sidescan-sonar datasets, 59 magnetic datasets, and 45 gravity datasets. More data will be added over time.
in this issue:
Coastal and Marine Geoscience Data System