Single-beam bathymetry, magnetics, and gravity data along with transit satellite navigation data was collected as part of field activity 84015 (L-9-84-CP) from Majuro to Honolulu, Central Pacific from 07/27/1984 to 08/16/1984.
These data are reformatted from space-delimited ASCII text files, located in the former Coastal and Marine Geology Program (CMGP) InfoBank field activity catalog, into MGD77T format for NOAA's National Geophysical Data Center (NGDC). The MGD77T format includes a header (documentation) file (.h77t) and a data file (.m77t). More information regarding this format can be found in the publication listed in the Cross_Reference section of this metadata file.
These data and information are intended for science researchers, students, policy makers, and general public. These data are not to be used for navigation purposes. The data are reformatted into MGD77T standard format for inclusion into NOAA's NGDC geophysical database.
The navigation data are digitally collected using a Satellite Integrated Navigation (SINS) system. The system is a space-based satellite navigation maintained by the United States government and is accessible using a satellite receiver. This system provides navigational accuracy of approximately 200 m.The Data Acquisition, Processing, and Storage (DAPS) group performs a number of processing steps to the navigation data once it is collected which can vary by cruise. These steps are outlined within the header information in each individual digital navigation (.05x) space-delimited ASCII data file. The header information rows are indicated by lines beginning with the character "!". There is no information on how the single-beam bathymetry, gravity, and magnetic data were collected. For each data gathering cruise leg, the available data in the following categories are forwarded to NGDC: navigation, gravity, magnetics, bathymetry, and seismic shot points. The available data for each cruise leg are re-formatted and combined into the Marine Geophysical Data Exchange Format (MGD77) and into the internal NGDC SEIS-NAV format by USGS using several USGS developed FORTRAN programs.The FORTRAN programs sample the navigation to every integer minute of the cruise. When necessary, the latitudes and longitudes are linearly interpolated. If the time between the actual navigation fixes exceeds five minutes, no data are included in the MGD77 file.To build the MGD77 file, gravity, magnetics, and bathymetry are added to this sampled navigation. When necessary, gravity, magnetics, and bathymetry data are linearly interpolated if the time between the actual data samples does not exceed five minutes. If a time gap exceeds this, the data are not reported.The navigation data are merged with the seismic shot point data in a SEIS- NAV format file. For this file, navigation data are interpolated for each shot point. Both types of files are written to magnetic tape and sent to NGDC.
Additional information about the field activities from which these data were derived is available online at
https://cmgds.marine.usgs.gov/fan_info.php?fan=1984-015-FA
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology.
