IMAA On-board Wave Height Sensor
The Wave Height Sensor was developed by IMAA supported by Nick Belson Design Ltd in 2002. The sensor
was first fitted to the Volvo 60' yachts taking part in the Volvo "Round the World Race" that year. Various
improvements have been developed and units have been fitted to all the yachts taking part in the "Round
the World" races between 2004 and 2009.
The Wave Height Sensor carries out a real-time analysis of the encountered wave conditions.
It incorporates accelerometers which sense the heave motion of the boat and through a heave response
function, determines the wave height and period. It operates at a sample rate of 5 points/sec and averages
the wave conditions over a two hour period. The "significant" values, recognized by sailors as the mean
of the well-formed waves, are then transmitted over the internet. During the first few days of the Race the
wave height was compared with available data from the Met. Office buoys in UK waters, and proved to be
remarkably accurate.
The Wave Height Sensor unit measures the following on-board parameters:
Significant and maximum wave height in a given period
Average encountered wave period
Average angle of heel and maximum heel in a given period
Maximum slam acceleration level recorded in a given period
Subjective Motion (SM) magnitude in a given period.
The SM is a measure of the on-board comfort level - 5 moderate - 10 serious - 15 severe etc. (see above graph)
The IMAA Wave Height Sensor can be adapted for use on any vessel. A knowledge of the relevant heave response function is required. IMAA has a wide range of information on such functions.
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