a100sc.m77t and a100sc.h77t: MGD77T data and header files for single-beam bathymetry data for field activity A-1-00-SC in Southern California from Port Hueneme to Mexican Border from 06/05/2000 to 06/29/2000

Single-beam bathymetry data along with DGPS navigation data was collected as part of the U.S. Geological Survey cruise A-1-00-SC. The cruise was conducted from Port Hueneme, California, to the Mexican border from June 5 to June 29, 2000. The chief scientists were Chris Gutmacher, Stephanie Ross, Brian Edwards all from the USGS Coastal and Marine Geology office in Menlo Park, CA.
The purpose of this cruise was to identify and map active and potentially active faults, folds, and submarine slide-prone areas that may threaten densely populated areas of Southern California. This survey was also taken to determine the pathways through which sea-water is intruding into aquifers of Los Angeles County in the area of the Long Beach and Los Angeles harbors. The geophysical source was a Knudsen 12 kilohertz (kHz) 320B/R echosounder.
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/a/a100sc/html/a-1-00-sc.meta.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.

本数据集包含美国地质调查局（U.S. Geological Survey，USGS）A-1-00-SC科考航次采集的单波束测深数据与差分GPS（Differential GPS，DGPS）导航数据。该航次于2000年6月5日至6月29日期间，从加利福尼亚州休纳梅港（Port Hueneme）出发，航行至美墨边境区域。本次航次的首席科学家为来自加州门洛帕克市USGS海岸与海洋地质办公室的Chris Gutmacher、Stephanie Ross与Brian Edwards。
本次航次的核心科考目标为识别并绘制南加州人口稠密沿岸区域周边的活动断层、潜在活动断层、褶皱构造以及海底易滑坡区域，上述地质体可能对沿岸人口密集区构成威胁；同时，本次勘测还旨在探明长滩港与洛杉矶港周边区域内，海水入侵洛杉矶县含水层的运移路径。
本次地球物理探测所用设备为Knudsen 12千赫（kHz）320B/R型回声测深仪。
本次数据已从美国海岸与海洋地质计划（Coastal and Marine Geology Program, CMGP）信息库野外活动目录（网址：http://walrus.wr.usgs.gov/infobank/a/a100sc/html/a-1-00-sc.meta.html）中的空格分隔ASCII文本文件，转换为美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）下属国家地球物理数据中心（National Geophysical Data Center, NGDC）制定的MGD77T格式。
MGD77T格式包含头文件（文档文件，后缀为.h77t）与数据文件（后缀为.m77t）两类。有关该格式的更多细节，可查阅本元数据文件“交叉参考”章节中列出的相关出版物。