Water makes up so much of the Earth's surface the description of it is, of course, closely tied to mapping. Water is dynamic and the tides are a very apparent expression of water's dynamic variation. At times, their presence or absence has wrecked havoc on the process of mapping. Especially, on drawing those ever so important lines that delineate boarders and boundaries between land and water. Let's take a little time to consider the several of the ways that tides are described, generated, measured and named.
tide 1. n., Tides, A periodic change in one celestial body caused by another celestial body or bodies. 2. n., Tides, A periodic change in the Earth or other planet, moon or celestial body, related to the locations of the Sun, Moon and other members of the Solar System, e.g., thermal tides are changes caused by heating and cooling of a body such as the Earth's atmosphere; gravitational tides are changes in figure and are caused by the attraction of other bodies. 3. n., Tides, A periodic change in the size and shape of the Earth or other planet, moon or celestial body caused by movement through the gravitational field of another body or bodies. Also called astronomic tide and astronomical tide. This should not be confused with gravitational tide. The word tide is most commonly used to refer to changes in size and shape of the Earth in response to the gravitational attractions of the other members of the Solar System, the Moon and Sun in particular. In this instance, three different tides are usually distinguished: the atmospheric tide -acting on the atmosphere; the earth tide -acting on the lithosphere; and the oceanic tide (usually called, simply, the tide) -acting on the hydrosphere. SEE ALSO tide, astronomical; tide, atmospheric; tide, radiational; tide, thermal. 4. n., Tides, The height or elevation of the land or a body of water at some instant and place as compared to the height or elevation averaged over a specified time interval (longer than one day and preferably over a period of at least 19 years). Also called water when referring to a body of water. 5. n., Tides, The surface of the land or a body of water, at some instant and place, as compared to the position of that surface averaged over a specified interval of time (longer than one day and preferably over a period of at least 19 years). Also called water when referring to a body of water. 6. SEE tide, oceanic. 7. SEE tide, gravitational. 8. SEE tide, thermal. 9. SEE water (1.). SEE ALSO age of the tide; amplitude of the tide; analysis of the tide, harmonic; cut tide; constituent (of the tide); constituent, diurnal; earth tide; ebb tide; equilibrium tide; equilibrium theory of the tide; flood tide; height of the tide; neap tide; line of the tide, nodal; range (4.); periodicity of the tide, pole tide; range of the tide; range of the tide, great diurnal; range of the tide, great tropic; range of the tide, small diurnal; range of the tide, small tropic; rise of the tide, mean; spring tide; spring tide, perigean; stand of tide; storm tide; type of tide.
tide, atmospheric 1. n., Tides, Those periodic changes in the Earth's atmosphere which are caused by the gravitational attraction of the Moon, Sun and other planets. Atmospheric tides are always so called; the word tide alone refers to oceanic tides specifically or to any one of the three basic kinds of tides: atmospheric, earth and oceanic. The most easily observed changes are changes in barometric pressure. 2. n., Tides, The periodic rising and falling of the Earth's atmosphere, regardless of the cause. This usage is uncommon. 3. n., Tides, Periodic changes in the atmosphere of any celestial body, caused by the effect of another body or bodies on it.
tide, compound n., Tides, A tidal constituent whose phase changes at a rate equal to the sum or difference of the rates at which the phases of two or more elementary constituents change.
tide, double 1. n., Tides, A high water consisting of two maxima of nearly the same height, separated by a relatively small depression. 2. n., Tides, A low water consisting of two minima of nearly the same depth, separated by a relatively small elevation. Sometimes called an agger.
tide, gravitational 1. n., Tides, A periodic motion of a level surface in response to the gravitational attraction of the Moon, Sun and other members of the Solar System. Also called an equilibrium tide. In particular, such a periodic motion of the figure of the earth. The gravitational tide is different from the earth tide and the oceanic tide; those tides are movements of the lithosphere and hydrosphere. It is almost the same as the astronomic tide. Spirit leveling gives the elevation of the Earth's surface with respect to the geoid and hence is affected by both earth tide and gravitational tide. 2. SEE tide, equilibrium. 3. SEE tide, astronomical.
tide, lunar n., Tides, That portion of the tide which can be attributed directly to the Moon's attraction. The term can, if used in a general sense, include both direct and indirect effects of the Moon's attraction.
tide, meteorological n., Tides, A tidal constituent having its origin in the local daily or seasonal variations in weather conditions. These conditions may occur with some degree of periodicity. The principal tidal constituents having a meteorological origin are Sa (solar annual), Ssa (solar semi-annual) and S1 (solar diurnal).
tide, radiational n., Tides, Periodic variations in water level related primarily to meteorological changes such as the semi-daily cycle in barometric pressure, daily breezes from the land and sea and seasonal changes in temperature. The term may be synonymous with meteorological tide.
tide, solar 1. n., Tides, That part of the oceanic tide which is caused by the Sun's attraction. 2. n., Tides, The oceanic tide observed in regions where the Sun's attraction is dominant.
tide, synodic n., Tides, That component of the tide which can be ascribed to changes in the phases of the Moon.
tide, thermal n., Tides, A change in the size and shape of the Earth resulting from the heating of the Earth by the Sun and the subsequent reradiating of this heat into space. At the present rate of rotation of the Earth, the lithosphere and hydrosphere are not affected much below a few tens of meters and so do not show appreciable thermal tides. The atmosphere, however, is heated throughout its depth and displays marked thermal tides. Thermal tides are difficult to distinguish from tides caused by gravitation.
As tides change, hopefully, we consider how they were generated and what they bring us and leave with us. And when we attempt to map this dynamic phenomenon hopefully we remember to keep in mind the many forces both from inside the earth and outside the atmosphere and the atmosphere itself are acting upon the tides that change the landscape, shoreline, and the lines drawn on the map.
In this blog we will post terms and themes of related terms and their definitions that come from the The Glossary of Mapping Sciences with commentary. In the hope that by discussing the meaning of words we come to deeper understanding and more meaningful usage.