What is the reference for heights on a chart?

Chart Datum (CD) is the plane of reference to which all charted depths and drying heights are related.

What is the difference between chart datum and mean sea level?

A chart datum is generally derived from some tidal phase. Common chart datums are lowest astronomical tide (LAT) and mean lower low water (MLLW). In non-tidal areas, e.g. the Baltic Sea, mean sea level (MSL) is used. A chart datum is a vertical datum and must not be confused with the horizontal datum for the chart.

What do nautical charts tell you?

In addition to water depths — including the shoreline — charts show the location of rocks, reefs, wrecks and other submerged obstructions, anchorages, channels, lighthouses, buoys, and even tide rips. The symbols and abbreviations for these features are often obvious but sometimes less so.

What is drying height on chart?

On a nautical chart, the drying height is the vertical distance of the seabed that is exposed by the tide, above the sea water level at the lowest astronomical tide. On admiralty charts a drying height is distinguished from a depth by being underlined.

What is the difference in height between consecutive high and low water?

Tidal period is the time interval between two successive high waters. In diurnal and semi-diurnal tides, it is the difference between the high water and the low water. Diurnal inequality — refers to the differences in height of the two high waters or of the two low waters of each day.

Where is tide height measured from?

The Height of Tide is an important tidal level and refers to the level of the tide is at any point in time. The height of tide is measured from Chart Datum which can be considered the same as the lowest astronomical tide LAT.

What does G mean on a nautical chart?

G Topographic Terms. HYDROGRAPHY. H Tides, Currents. I Depths. J Nature of the Seabed.

What does Foul mean on a nautical chart?

Foul is a nautical term meaning to entangle or entwine, and more generally that something is wrong or difficult.

What is tide height?

Fig 5.10 – The depth of water at any point is the Charted Depth + the Height Of Tide. At the pinnacle of rock we can see that the Height Of Tide – Drying Height = the Depth of Water over the pinnacle of rock.

How are tide heights measured?

The standard way to measure sea level is with an instrument called a tide gauge. These are used in ports and harbours the world over and record the heights of the falling and rising tides. The gauge worked by recording the rise and fall of the sea with two floats attached by chains.

How tide heights are measured?