from Hacker News

Surfers ride 100ft wave in Portugal

by awicklander on 10/30/13, 5:37 AM with 1 comments

• by snowwrestler on 10/30/13, 2:26 PM

  I think it's really unlikely that wave is 100 feet. In fact it looks to me like it will measure out to be lower than the previous record holder at that same spot.

  The trick here is that the viewing and photo spot is on a bluff well above the ocean, so any photo of a wave will include a large portion of the trough in front of it. This makes the face look a lot taller than it actually is, because there are no distinguishing marks on the surface of the water to tell the face from the trough.

  In addition there is the question of face height vs. wave height. Wave height is measured above mean sea level--they are measured from the back, not the front. Waves are preceded by troughs, so a 5 foot wave might actually have a 7 to 8 foot face. In this case it's pretty clear that "100ft" is referring to the face.