Tras leer la noticia de que el dia 24 de Enero el temporal provoca una ola de 26mts  de altura   a 22 millas al norte de San Sebastian.¿alguien sabe como se toman esas  medidas?.
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Este tema me está gustando mucho, porque las boyas meteorológicas son juguetes meteorológicos carísimos que me fascinan. Si fuera un sucio ricachón ( ) tendría el Mar de Alborán sembrado de boyas de éstas . Poniéndome las pilas, he encontrado que las boyas miden la altura de las olas mediante varias técnicas, como altímetros sónicos (ni idea de cuál es la ciencia de su funcionamiento). Extraigo esto de la Wikipedia:

A more common and robust way of measuring waves is using a buoy that records the motion of the water surface, which does not require a fixed platform. The buoy motion provides a time history of the water elevation for that location and statistics can be calculated including the significant and maximum wave heights and periods. Modern waverider buoys usually measure their movement along three dimensions and give information about wave direction. For the south east Queensland coastline there are waverider buoys about every 100 km along the coast. The waverider buoys are typically positioned off the entrances of major ports or major recreational surfing or swimming beaches. A network of waverider buoys properly positioned can allow the interpolation of the wave climate for that region. Waverider buoy data is a typical input for coastal modelling, the waverider wave train is typically the deep water wave climate that is refracted across the seabed contours into the wave breaking zone.


significant wave height—Defined traditionally as the mean height of the highest third of the waves, but now usually defined as four times the root-mean-square of the surface elevation (or equivalently as four times the square root of the first moment of the wave spectrum).


Boya meteorológica del NOAA.

Wave recording
The Environmental Protection Agency's wave recording program uses one of two systems to measure wave data:
the Waverider buoy system;

a wave pole.

The Waverider system uses a Waverider buoy to determine the sea surface fluctuations at an offshore location. Directional and non-directional buoys are in operation.

Directional and non-directional Waverider buoys measure vertical acceleration by means of an accelerometer. The accelerometer is mounted on a gravity-stabilised platform that is suspended in a fluid-filled plastic sphere. The sphere is located at the base of the buoy. This data is then processed to give vertical displacement (Wave height). (See Glossary for technical details.)

The directional buoy measures horizontal acceleration using two accelerometers and an onboard compass to give the directional displacement in two horizontal axes. With this information, the north-south and east-west directions are calculated. The water level and directional data are then transmitted to the shore station as a high-frequency radio signal.

http://www.epa.qld.gov.au/environmental_management/coast_and_oceans/waves_and_storm_tides/wave_monitoring/waverider_buoys/#gen1

Según tengo entendido, la altura de una ola no se puede medir con exactitud y precisión, si no que se estima la misma.

¿Es esto cierto?

Si la boya está bien instalada, puede medir la altura de todas las olas. Otra cosa es que la altura más alta de las olas no se puede tomar como referencia para definir el estado del mar (escala Douglas), y para ello se habla de la altura significante de las olas, que se obtiene de promediar la altura del 33% de olas más altas registradas en un periodo determinado (1 hora, 5 minutos o 2 dias)
De todos modos, el récord que se menciona de 26,13 metros fue tomado por una boya a la deriva (se le rompieron los amarres el 22 de enero), instalada originalmente 22 millas al norte de Santander, y recuperada (con toda la información en su datalogger) en la costa guipuzcoana el día 28. Desconozco hasta que punto esta información se considera plenamente veraz, pero yo no soy nadie para juzgarlo.