![]() In general, as the tides rise there will be a current flowing from the oceans into the bays, harbors and estuaries this is termed a "flood current". The vertical rise and fall of the tides, created by the gravitational force of the Moon and Sun acting on the oceans water, also creates a horizontal motion of the water in the bays, harbors and estuaries. These printed tables were produced annually from 1867 until 2020. These books provided tide or current predictions for a wide variety of locations, and included tide predictions for international locations provided by the Oceanographic agencies in those countries. The term “Tide Tables” and “Current Tables” were also used to refer to the series of annually published NOAA Tide Tables / Current Tables books. "Current Tables" can be generated for more than 2,500 locations around the USA, and are available from the NOAA Current Predictions service of our website. "Current Tables" refer to tidal current predictions tables, which provide a listing of the times and speeds of the daily flood, ebb, and slack currents, or hourly interval currents speeds, for a particular location. "Tide Tables" can be generated for more than 3,000 locations around the USA, and are available from the NOAA Tide Predictions service of our website. "Tide Tables" refer to tidal predictions tables, which provide a listing of the times and heights of the daily high and low tide predictions, or hourly interval tidal height values, for a particular location. The only “Tide Charts” and “Current Charts” presently generated are the Water Level or Currents – Nowcast & Forecasts Guidance available from our Operational Forecast Systems (OFS). However those publications were removed in 1990 due to inaccurate information presented in these publications. NOAA used to provide printed Tidal Current Charts for 9 areas of the U.S. These maps normally show the currents (speed and directions) on an hourly basis. “Current Charts” refer to a series of maps that show the currents speed and direction throughout a bay or estuary at a particular point in time. NOAA has never produced a printed tide chart publication. "Tide Charts" refer to a series of maps that show the water levels throughout a bay or estuary at a particular point in time. "Tide Charts" and "Tide Tables" are two different products, as are “Current Charts” and “Current Tables”. VDatum uses modeling techniques to calculate a relationship between tidal and geodetic datums at a desired location, based on the near-by locations with a measured relationship between tidal and geodetic datums. VDATUM is a free software tool and online service developed jointly by NOAA's National Geodetic Survey (NGS), Office of Coast Survey (OCS), and Center for Operational Oceanographic Products and Services (CO-OPS). In which case, there is one additional option available - the Vertical Datum Transformation (VDATUM) tool. ![]() Many stations, particularly older or temporary stations, lack the survey benchmarks necessary to establish the relationship between tidal and geodetic datums. Unfortunately, not all stations are able to meet these standards. When survey leveled from these markers to the tide station, the relationship calculations for these marks must match within 9 millimeters. If the individual benchmark has a NGS record, this is recorded by the IDP or OPUS PID numbers of that mark. The survey benchmarks associated with each station are provided in the Benchmark Sheets for a station. Our standard requires a minimum of 2 survey benchmarks, installed within a short distance of the station, which have a NAVD88 elevation recorded by the National Geodetic Survey (NGS). If that field is blank, then no relationship has been established. This relationship is noted on the Tidal Datums for that station, by providing an elevation of NAVD88. Where possible we provide a relationship between tidal datums and the geodetic datum of NAVD1988. ![]() NOAA, and it predecessor organizations, have been measuring tide data long before the development of a standard geodetic datum, such as NAVD1988. ![]()
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