Single-beam bathymetry, gravity, and magnetic data along with DGPS navigation data was collected as part of field activity L-4-77-NC in Northern California from 05/10/1977 to 05/21/1977, http://walrus.wr.usgs.gov/infobank/l/l477nc/html/l-4-77-nc.meta.html These data are reformatted from space-delimited ASCII text files located in the Coastal and Marine Geology Program (CMGP) InfoBank field activity catalog at http://walrus.wr.usgs.gov/infobank/l/l477nc/html/l-4-77-nc.bath.html, http://walrus.wr.usgs.gov/infobank/l/l477nc/html/l-4-77-nc.grav.html, and http://walrus.wr.usgs.gov/infobank/l/l477nc/html/l-4-77-nc.mag.html into MGD77T format provided by the 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.