| Abstract from DBPedia | A radar altimeter (RA), also called a radio altimeter (RALT), electronic altimeter, reflection altimeter, or low-range radio altimeter (LRRA), measures altitude above the terrain presently beneath an aircraft or spacecraft by timing how long it takes a beam of radio waves to travel to ground, reflect, and return to the craft. This type of altimeter provides the distance between the antenna and the ground directly below it, in contrast to a barometric altimeter which provides the distance above a defined vertical datum, usually mean sea level.電波高度計（でんぱこうどけい radar altimeter）は電波を用いた高度計。航空機もしくは宇宙船より地上へ電波を発し、自機の対地高度を測定する。レーダーの一種。 (Source: http://dbpedia.org/resource/Radar_altimeter) |
