Dead reckoning is a method of determining a current position, speed, or time by using known previous information and subsequent measured movement inputs. Conceptually, it involves predicting a future location based on a starting point and estimated vectors of travel, primarily requiring knowledge of elapsed time, speed, and direction. Because it relies solely on internal measurements and calculations derived from movement data, the accuracy of a dead reckoning estimate degrades over time due to the accumulation of errors, such as inconsistencies in velocity calculation or directional drift. Historically and technologically, the concept has been fundamental to navigation systems in various forms, serving as a critical backup or preparatory measure before external positional fixes, such as those provided by celestial observation or satellite systems, can be obtained.