Sastrugi breaking equipment—ripples and waves are often undercut and the surface is hard and unforgiving, with constant minor topographic changes between ridge and trough. The words "sastrugi" and "zastrugi" are Russian-language plurals; the singular is "sastruga" or "zastruga". The form "sastruga" started as the German-language transliteration of the Russian word заструга (plural: заструги). A Latin-type analogica singular "sastrugus" is used in various writings on exploration of the South Pole, including Robert Falcon Scott's expedition's diaries and Ernest Shackleton's "The Heart of the Antarctic". Under the action of steady wind, free snow particles accumulate and drift like the sand grains in barchan
Surface wave detection by animals to test certain wave properties. Wave characteristics are measured optically. This is done by shining a laser (often helium-neon) at the water surface. Reflections and distortions of the laser’s beam are picked up by a photodiode. Fishes' movements are videotaped with a high-speed camera from above the testing tank so that the precise timing and nature of their responses’ to stimuli can be reviewed. "Aplocheilus lineatus" assumes a hunting posture at the water surface in which it holds the top of its head within 200 μm of the water surface. On perception of appropriate wave stimuli, fish first turn towards