Tidegauges

Tidegauges are instruments used to measure the height of the tide. They are essential for navigation, coastal engineering, and scientific research. Historically, tidegauges were simple devices like graduated staffs fixed to a pier or wall, allowing observers to read the water level directly. Modern tidegauges are more sophisticated and can be automatic.

There are several types of tidegauges. Floats are common, where a float rests on the water surface and its vertical movement is translated into a reading, often by a pen on a rotating drum or a digital sensor. Pressure gauges are also widely used; they measure the hydrostatic pressure exerted by the water column above the sensor, which is directly related to the water depth. Acoustic tidegauges use sound waves to measure the distance to the seabed, and then calculate the water depth. Radar tidegauges work similarly by measuring the time it takes for a radar pulse to travel to the water surface and back.

Tidegauge data is crucial for establishing tidal datums, such as mean sea level and high and low water levels, which are used for charting and defining coastlines. They also provide valuable information for predicting future tides, understanding tidal patterns, and monitoring sea-level rise. Networks of tidegauges are operated by national hydrographic offices and meteorological agencies worldwide.