Editing Tide gauge (section)

==Operation==
Sensors continuously record the height of the [[water level]] with respect to a height reference surface close to the [[geoid]]. 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|date=May 2018}}

Historical data are available for about 1,450 stations worldwide, of which about 950 have provided updates to the global data center since January 2010.<ref>{{cite web|title=Obtaining Tide Gauge Data|url=http://www.psmsl.org/data/obtaining/|website=Permanent Service for Mean Sea Level|publisher=PSMSL|access-date=2016-03-07|ref=PSMSL_data}}</ref> At some places records cover centuries, for example in [[Amsterdam]] where data dating back to 1700 is available.<ref>{{cite web|url=http://www.psmsl.org/data/longrecords/|title=Other Long Records not in the PSMSL Data Set|access-date=2015-05-11|publisher=PSMSL}}</ref>

When it comes to estimating the greater ocean picture, new modern tide gauges can often be improved upon by using satellite data.{{citation needed|date=May 2018}}

Tide gauges are used to measure [[tides]] and quantify the size of [[tsunami]]s. The measurements make it possible to derive the mean [[sea level]]. Using this method, sea level slopes up to several 0.1 m/1000&nbsp;km and more have been detected.{{citation needed|date=May 2018}}

A tsunami can be detected when the sea level begins to rise, although warnings from [[seismic activity]] can be more useful.{{citation needed|date=May 2018}}