A form of navigation that determines position of a craft by advancing a previous position to a new one on the basis of assumed distance and direction moved. The name probably stems from the early practice of determining speed by throwing overboard a buoyant object, called a Dutchman's log, and noting the time needed for a known length of the vessel to pass the floating object, or attaching a line to the object (when the whole device became known as a chip log) and noting the amount of line paid out in a given time. In either case, the floating object was assumed to remain dead in the water, thus providing an indication of speed through the water. The reckoning of future positions of the vessel by means of this speed was known as dead reckoning.