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standard port original
dcterms created equal to or less than 2020-09-09T01:02:45.479Zequal to or more than 2020-09-09T01:02:45.479Z
definition In the context of tide tables, a port for which sufficient data is available in order for a set of official predictions to be produced. Also known as a "primary port", especially in North America.
slack water original
dcterms created equal to or less than 2020-09-09T01:02:45.477Zequal to or more than 2020-09-09T01:02:45.477Z
definition From the "Australian Hydrographic Office Glossary": The state of a tidal stream when its speed is zero or nearly so, especially the moment when the reversing stream changes its direction. Also known as slack tide or slack. see also streams.
stand of tide original
dcterms created equal to or less than 2020-09-09T01:02:45.479Zequal to or more than 2020-09-09T01:02:45.479Z
definition From the "Australian Hydrographic Office Glossary": The condition at high or low water when there is no perceptible change in the height of tide for a period of time. Sometimes called platform tide. see also streams.
absolute sea level original
dcterms created equal to or less than 2020-09-09T01:02:45.439Zequal to or more than 2020-09-09T01:02:45.439Z
definition When sea level is referenced to the centre of the Earth, it is sometimes referred to as “absolute”, as opposed to “relative”, which is referenced to a point (eg. a coastal benchmark) whose vertical position may vary over time.
acoustic tide gauge original
dcterms created equal to or less than 2020-09-09T01:02:45.439Zequal to or more than 2020-09-09T01:02:45.439Z
definition A unit which sends an acoustic pulse through free air down a sounding tube to the water’s surface and measures the return time. The return travel time though the air between a transmitter/receiver and the water surface below is converted to sea level.
admittance original
dcterms created equal to or less than 2020-09-09T01:02:45.439Zequal to or more than 2020-09-09T01:02:45.439Z
definition Used in the response method of tidal analysis, response method analysis consists of determining a set of complex weights (typically five), which define the admittance of the response system at a given frequency. Once known, the admittance, combined with the known coefficients on the spherical harmonics representing the tide-generating potential, can be used to deduce the amplitude and phase of the usual harmonics (M2, S2, etc.). Admittance is sometimes defined as the ratio of the spectra of the sea level and the equilibrium tide (or tide-generating potential), and sometimes as the ratio of their cross-spectrum and the spectrum of the equilibrium tide. Being a complex quantity, it has both amplitude and phase.
age of the tide original
dcterms created equal to or less than 2020-09-09T01:02:45.440Zequal to or more than 2020-09-09T01:02:45.440Z
definition The delay in time between the transit of the moon and the highest spring tide. Normally one or two days, but it varies widely. In other words, in many places the maximum tidal range occurs one or two days after the new or full moon, and the minimum range occurs a day or two after first and third quarter. In a semi-diurnal tidal environment dominated by M2 and S2, the age in hours can be computed using the formula (gS2 – gM2)/(ѠM2 - ѠS2), where gS2 and gM2 are the phase lags (in degrees) from an analysis of the data, and ѠM2 and ѠS2 are the speeds (in °/hour). A similar formula can be devised for a diurnal environment dominated by O1 and K1.
alias frequencies original
dcterms created equal to or less than 2020-09-09T01:02:45.440Zequal to or more than 2020-09-09T01:02:45.440Z
definition Tidal frequencies that contain significant energy and are of higher frequency than the Nyquist frequency, they result from folding of lower frequencies in the power spectrum.
amphidrome original
dcterms created equal to or less than 2020-09-09T01:02:45.440Zequal to or more than 2020-09-09T01:02:45.440Z
definition Maps of specific tidal constituents (eg. M2) are normally drawn with lines connecting points of constant amplitude (co-range or co-amplitude lines) and/or phase (co-phase lines). The co-phase lines often appear like spokes radiating out from a central hub - the "amphidrome" or "node". Often a single map will show a number of these "amphidromic systems". The co-range lines more or less encircle the amphidrome, where the constituent amplitude is least.
Amphidromes are resonance phenomena, with higher-frequency constituents tending to have lesser areal extent. Whereas O1 has an amphidrome virtually over the entire North Atlantic Ocean, M2 has two.
amplitude original
dcterms created equal to or less than 2020-09-09T01:02:45.440Zequal to or more than 2020-09-09T01:02:45.440Z
definition From the "Australian Hydrographic Office Glossary": One half of the range of a constituent, tide or wave in general.