How do tide gauges which measure the pressure of water (and hence the water height) take account of atmospheric pressure?
Tide gauge pressure sensors are either ‘absolute’ systems (ie. they measure the total pressure under water which of course includes the pressure load of the atmosphere), or ‘differential’ systems which measure the water-head pressure alone by subtracting the atmospheric pressure from the total pressure within the pressure transducer. An alternative form of ‘differential’ sensor can be constructed with the use of an ‘absolute’ sensor together with a separate barometer. Either way, it is important to realise that ‘sea level’ is not the same as ‘sub-surface total pressure’. For more detailed information on tide gauge measurement techniques, see the ‘IOC Manuals and Guides No.14’ (especially Volume 3 which is the most recent).
Related Questions
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