NOS Hydrographic Survey Data

The National Geophysical Data Center (NGDC) maintains the National Ocean Service Hydrographic Data Base (NOSHDB) and Hydrographic Survey Meta Data Base (HSMDB). Both databases are populated by Office of Coast Survey with information acquired from its surveys and National Geodetic Service remote sensing. The databases provide extensive survey coverage of the coastal waters and exclusive economic zone of the United States and its territories.

The NOSHDB contains digitized data from smooth sheets of hydrographic surveys completed between 1837 and 1965, and from survey data acquired digitally on NOAA survey vessels since 1965.

Over 76 million soundings from over 6,600 surveys are included in the NOSHDB. NGDC has developed an interactive map and data discovery tool, the Bathymetry Map Service, and a text-based search engine, the Hydrographic Survey Text Search, which enable rapid data discovery and download. The NOSHDB data with search and retrieval software are also available on DVD-ROM.

The HSMDB provides ISO metadata records, text search, and display of NOAA data and products.

Hydrographic Survey Rap Sheets display survey summaries and locations, cross references, statistics, comprehensive platforms and correctors, processing and archive information. Survey types include Hydrographic, Field Edit, Reconnaissance, Lake, and Non-NOS sources.

Data products from NOS surveys, including BAG files, Descriptive Reports, smooth sheet images, survey data images, textual gridded data, and geo-referenced sidescan sonar mosaics, FGDC/RSE metadata, and survey statistics are available for download from NGDC.

Bathymetric Attributed Grid (BAG) is a non-proprietary file format for storing and exchanging bathymetric data developed by the Open Navigation Surface Working Group. BAG files are gridded, multi-dimensional bathymetric data files and is the standard NOS hydrographic data file for public release. Current versions of the BAG file contain position and depth grid data, as well as position and uncertainty grid data, and the metadata specific to that BAG file, providing end users information about the source and contents of the BAG file. Please visit the Open Navigation Surface Working Group for additional information on BAG files.

NGDC has developed the capability to output data from BAG files as American Standard Code for Information Interchange (ASCII) xyz files. Empty space in BAG files is not included in xyz output files. On NGDC's web site, individual files, or entire surveys spanning multiple BAG files, can be selected, extracted, processed to xyz format, and zipped for shipment using the new conversion capability. Each conversion also creates an Extensible Markup Language (XML) metadata file.

Descriptive Reports (DRs) are approved metadata documents relevant to survey level hydrographic data and are available in Portable Document Format (PDF) form. The DR serves as a narrative document that describes the conditions under which the hydrographers performed the work and discusses various factors affecting the adequacy and accuracy of the results.

Smooth Sheets are available from NGDC as images in Tagged Image File Format (TIFF) or Multi-resolution Seamless Image Database (MrSID) format. A smooth sheet is the final, neatly drafted, accurate plot of a hydrographic survey using verified or corrected data.

NGDC archives and disseminates over 11,000 smooth sheets and over 8,000 DRs dating from the mid-1800s to the present. The survey data images, gridded data, and sidescan sonar mosaics are available only for recent surveys where NOS collected high-resolution data.

Related Links:

• NOS Office of Coast Survey (OCS) - home page
• OCS Chart Viewer - view current navigational charts online
• OCS RNCs - obtain navigational charts online
• OCS ENCs - view/download navigational chart layers online