Description: Layer represents the geographic location of all water level stations at
which datums have been calculated. For marine applications, a datum is a base
elevation used as a reference from which to reckon heights or depths. It is called a tidal datum when defined in terms of a certain phase of the tide. Tidal datums are local datums and should not be extended into areas that have differing hydrographic characteristics without substantiating measurements. In order that they may be recovered when needed, such datums are referenced to fixed points known as benchmarks. The "Present Epoch" is from 1983-2001 and includes the latest datums available. The "Superseded Epoch" is from 1960-1978 and has been replaced by the "Present" datums, or was not replaced due to insufficient data. More information can be found at http://tidesandcurrents.noaa.gov/datum_options.html and
http://www.tidesandcurrents.noaa.gov/publications/Computational_Techniques_for_Tida l_Datums_handbook.pdf
Description: Layer represents the geographic location of all water level stations that
have published bench mark sheets. The published tidal bench mark sheet is a final
documented compilation of tidal datum elevation and tidal bench mark information
based on the accepted tidal datums computed from tide station observations. More information can be found at
http://tidesandcurrents.noaa.gov/stations.html?type=Bench+Mark+Data+Sheets
Description: Layer represents the geographic location and values of extreme water
levels at the 1%, 10%, 50%, and 99% probabilities at CO-OPS water level stations. Exceedance probability, the likelihood that water levels will exceed a given elevation, is based on a statistical analysis of historic values. This product provides annual exceedance probability levels for select CO-OPS water level stations with at least 30 years of data. The extreme levels measured by the CO-OPS tide gauges during storms are called storm tides, which are a combination of the astronomical tide, the storm surge, and limited wave setup caused by breaking waves. They do not include wave runup, the movement of water up a slope. More information can be found at
http://tidesandcurrents.noaa.gov/est/Extreme_Water_Levels_Users_Guide.pdf and
http://tidesandcurrents.noaa.gov/est/
Description: Layer represents the geographic location of stations at which tidal current
predictions can be generated from historic and active stations. Tidal current predictions are a calculation of what the current direction and speed will be based on the analysis of data collected at these locations. Harmonic stations generate predictions from harmonic constituents from the data analysis; Subordinate stations generate predictions using time and speed adjustment applied to the predictions for a specific harmonic station. CO-OPS offers predicted time and speed of maximum flood/ebb and timing of slack water (no current) and at regular intervals for all stations in NOAA's annually published tidal current tables and in NOAA Current Predictions service of the CO-OPS Tides & Currents website. The CO-OPS site is updated every quarter; during the first two weeks
of January, April, July and October. The quarterly updates may include the addition of new stations, updating subordinate and harmonic stations, and removal of superseded stations. More information can be found at
http://tidesandcurrents.noaa.gov/noaacurrents/Help
Description: Layer represents the geographic locations of stations at which tide
predictions can be generated from historic and active water level stations. Tide
predictions are a calculation of what the water level will be based on the analysis of data collected at these locations. Harmonic stations generate predictions from harmonic constituents from the data analysis; Subordinate stations generate predictions using time and height adjustments applied to the predictions for a specific harmonic station. CO-OPS offers six-minute and hourly tide/water level predictions "on-the-fly" for all stations with harmonic constituents. CO-OPS also offers high/low data for all stations in NOAA's published tide and current table. The CO-OPS site is updated every quarter; during the first two weeks of January, April, July and October. The quarterly updates may include the addition of new stations, updating subordinate and harmonic stations, and removal of superseded stations. More information can be found at
http://tidesandcurrents.noaa.gov/tide_predictions.htmlremoval of superseded stations. More information can be found @ http://tidesandcurrents.noaa.gov/tide_predictions.html
Description: Layer represents the geographic locations of removed and presently
operating water level stations at which harmonic constituents have been generated and accepted. A harmonic constituent is one of the harmonic elements in a mathematical expression for the tide-producing force and in corresponding formulas for the tide or tidal current. Each constituent represents a periodic change or variation in the relative positions of the earth, moon, and sun. A single constituent is usually written in the form y = A cos (at + "), in which y is a function of time as expressed by the symbol t and is reckoned from a specific origin. The coefficient A is called the amplitude of the constituent and is a measure of its relative importance. The angle (at + ") changes uniformly and its value at any time is called the phase of the constituent. The speed of the constituent is the rate of change in its phase and is represented by the symbol "a" in the formula. The quantity is the phase of the constituent at the initial instant from which the time is reckoned. The period of the constituent is the time required for the phase to change through 360° and is the cycle of the astronomical condition represented by the constituent. More information can be found at
http://tidesandcurrents.noaa.gov/stations.html?type=Harmonic+Constituents