Tide gauge

Water enters the device by the bottom pipe (far end of the tube, see picture), and electronic sensors measure its height and send the data to a tiny computer.

[citation needed] A tsunami can be detected when the sea level begins to rise, although warnings from seismic activity can be more useful.

[11] Tidal poles and float gauges were the primary means of sea-level measurement for over 150 years and continue to operate at some locations today.

An example is the Cascais tide gauge in Portugal, which was originally installed because of the sand bar in the River Tagus that causes difficulties for shipping entering Lisbon port.

Because of similar problems many industries have installed private tide gauges in ports around the world, and also rely on government agencies (such as NOAA).