Knot (unit) fluids (tidal streams, river currents and wind speeds) are also measured in knots. Thus, speed over the ground (SOG) (ground speed (GS) in aircraft) and rate of progress towards a distant point ("velocity made good", VMG) are also given in knots. Until the mid-19th century, vessel speed at sea was measured using a chip log. This consisted of a wooden panel, attached by line to a reel, and weighted on one edge to float perpendicularly to the water surface and thus present substantial resistance to the water moving around it. The chip log was cast over the stern of the
Wind power in Australia southern coastline lies in the roaring forties and hundreds of sites have average wind speeds above 8 or even 9 m/s at 50 m above ground (the hub height of a modern wind generator). The southwest of Western Australia, southern South Australia, western Victoria, northern Tasmania and elevated areas of New South Wales and Queensland have good wind resources. Several states engaged in systematic wind speed monitoring in the 1980s and 1990s, the results of which are publicly available. Australian wind farms produce on average capacity factors of 30–35%, making wind an attractive option. South Australia's large share (along with