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Documentation of the U.S. Geological Survey Oceanographic Time-Series Measurement Database

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Database Contents

Oceanographic time-series data collected as part of the Coastal and Marine Geology Program (CMGP) describe the movement and physical properties of the waters of the coastal ocean. In this document, "time series" refers to data collected at a single location for a time period of some duration. The location is defined by latitude, longitude, and depth, and the time is defined by sampling at some time interval for the duration of data acquisition.

The studies for which these data were collected focused primarily on improving the understanding of sediment transport and associated processes; therefore, the measurements are concentrated near the seafloor with fewer observations in the water column. The data files in this database include some or all of the following measurements: current velocity, temperature, pressure, conductivity, and light transmission (beam attenuation), as well as other parameters. For more detail, see the Content Overview section.

The time-series observations in this database have been processed to a state referred to as the "Best Basic Version" (BBV). The BBV files have been trimmed to include only data collected while the mooring or tripod was settled on the seafloor: data collected during pre- and post-deployment periods are removed. When possible, spikes were interpolated over and sensor-based failures are replaced with special values, typically 1e35 that indicate a substitution was made. If one sensor failed earlier than the rest, the part of that sensor's data after the failure will be replaced with the designated indicator values, and all of the data in the other variables will be retained. For example, if conductivity fails after 1 month, and the temperature data from the same instrument remains good for 3 months, just the last 2 months of conductivity would be replaced. In addition, vector-averaged currents are computed from burst current measurements; salinity is computed from conductivity, temperature, and pressure; and beam attenuation is computed from light transmission. The data sets are distributed at the instrument's configured sampling rate, and in some cases, as hourly averages. In the case of new instrumentation, the data may be released in provisional status prior to release as a BBV so that colleagues can assist in the evaluation of the data.

A mooring or platform deployed on the sea bed-- for example a bottom tripod frame-- typically supports multiple instruments and sensors. The data are stored in files derived from the instrument system logging the data, therefore several data files are usually associated with each platform. A file derived from an Acoustic Doppler Current Profiler (ADCP) current meter contains only the variables collected by the ADCP (east, north, and vertical current, transducer temperature, and attitude measurements). For a Conductivity-Temperature Logger, the file contains measurements of temperature, conductivity, and in some cases light transmission and pressure. The file name contains information on the platform and the type of data logged. Appendix 1 documents the nomenclature conventions used for files in this database. Because some terms in this report may be unfamiliar, a glossary of acronyms, abbreviations and conversion factors is provided in Appendix 2. The index page of the oceanographic time-series data server is organized region and by experiment. The files containing measurements from each experiment are made available by following the link to that experiment's page. Additional information is available in data reports produced as part of some of the programs; these are listed in Appendix 3.

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This page last modified on Thursday, 12-Feb-2009 13:04:53 EST