Recent Variations in Mean Sea Level in Southern Africa
The primary reference surface, or vertical datum, for heights is the geoid, which coincides closely with mean sea level. In fact, in many applications the terms are taken as synonymous, although the two may depart from each other by as much as two metres. National or regional vertical datums are usually established by making the implicit assumption that the geoid and mean sea level (MSL) coincide at one or more tide gauge sites, and the tidal records are then used as a basis for heights. As a consequence, any variability in the MSL, temporal or spatial, must be of concern to geodesists and surveyors, as it affects the stability of the vertical datum. Long term trends are also of concern to oceanographers and (taking into account the possible consequences of global warming) also exercise the minds of environmentalists and politicians.
KeywordsRoot Mean Square Tide Gauge Vertical Data Data Bias African Philosophical
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