A downward-looking radar mounted on a pier or structure that times reflections from the water surface to measure the air gap, from which water level follows. Nothing touches the water, so there is no fouling, no density correction and little maintenance, and it serves as the primary sensor across many networks. It needs a clear view of open water and careful levelling of its reference point to the bench marks.
Swap the acoustic for a microwave radar sensor, the sounding tube keeps fouling in summer.
Also heard as
- radar gauge
- microwave water level sensor
- radar sensor
Related terms
Tide gauge
An instrument that records water level continuously at a fixed point, the basic tool of tidal measurement.
Stilling well
An upright tube fed through a narrow bottom intake, filtering out waves so the gauge inside sees only the slow tide.
Leveling
Precise measurement of height differences between bench marks and the gauge or staff using a level and rods.
Six-minute data
Water level values recorded every six minutes, the standard sampling interval at many tide stations.