tide heights. A chart datum is generally derived from some tidal phase, in which case it is also known as a tidal datum. Common chart datums are lowest astronomical...

In geodesy, surveying, hydrography and navigation, vertical datum or altimetric datum is a reference coordinate surface used for vertical positions, such...

the vertical geodetic datum accuracy of some offshore areas as represented on nautical charts, especially on small-scale charts. A similar incident involving...

An ordnance datum (OD) is a vertical datum used by an ordnance survey as the basis for deriving altitudes on maps. A spot height may be expressed as above...

global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation...

geometric dimensioning and tolerancing Chart datum, level of water depth on a nautical chart Datum or datum point, a (possibly arbitrary) reference baseline...

geodetic datum or geodetic system (also: geodetic reference datum, geodetic reference system, or geodetic reference frame) is a global datum reference...

Port Chart Datum in depth, a turning basin of 600 m in diameter and also at -18 m Port Chart Datum, 1 general cargo berth at -18 m Port Chart Datum, and...

below" is most often noted on charts as measured from the surface of the water to the under side of the bridge at the chart datum Mean High Water (MHW), a...

water levels ranged from 1.58 feet (0.48 m) to 0.33 feet (0.10 m) below Chart Datum. In the summer of 2007 monthly historic lows were set; August at 0.66...