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 Thailand resource map with 13 year-long data (1966-1978) from 53 wind speed measurement stations of the TMD, using power law to standardize all wind speed to 10 m. In 1984, another similar attempt was carried out by KMITT, using 17 year-long (1966-1982) data from 62 measurement stations, and with financial support from USAID. Attempts at producing wind resource maps of Thailand all faced the problem of shortage in wind speed data, especially offshore and at high elevations. This resulted in maps with low coverage. In 2001, another set of wind resource maps was produced by DEDE using data from over 150