Hawaiian scale
Hawaiian scale is the conventional wave height measurement used by surfers in Hawaii, also used in Australia and parts of South Africa.
The measurement is always in feet and scaled so the actual height on the face is roughly twice what's quoted. So a 3-foot wave would be head high (to a 6-foot person), or 2-foot around chest high. 6 to 8 foot would be 2 to approaching 3 times head high. Large waves are difficult to judge though, and the measurement becomes a little fuzzy towards 20 feet.
The origin of the scale is obscure. The candidates are:
- Hawaiian life guards calling smaller sizes to keep tourists away.
- The measurement is "from the back" of the wave, or from wave buoy readings.
- Macho understatement by early surfers.
In Australia, which is otherwise metric, feet are still used by surfers and surf-specific media (e.g. ASL and Tracks magazines). Some of the non-surfing media make an attempt at metrication by direct conversion (e.g.[1]), so 3 feet becomes 1 metre. In a sense that satisfies neither surfers who don't use those units, nor non-surfers don't know it means twice that on the face.
References
- Hawaiian Scale: Measuring Wave Heights in Hawaii by Neal Miyake, 2003