Abstract: An electrical odometer for use in wheeled vehicles, including a transducer coupled in some manner to a wheel of the vehicle such that angular rotation of the wheel produces a series of discrete signals. The discrete signals are transformed into a first pulse train having a wave form shaped for driving a logic element. Optionally, the conditioned pulses may be divided so as to create a dependent pulse train which is then processed to produce a series of trigger pulses having approximately equal duration. A computer means for performing arithmetic operations is also provided, along with some switching means for selectively causing the computer means to perform an arithmetic operation upon the occurrence of each incoming pulse. A digital display is connected with the computer means, for displaying distance values. A means such as a numeric keyboard is provided for manually entering an initial distance value into the digital display.

Abstract: Two signals are correlated in a properly programmed digital computer to render a result reflecting the difference in time of arrival of the two signals at separate receiving stations from a common emitter station. Signals received at each of the receiver stations are converted into digital data and transmitted via a data link to a central correlation station. At the central correlation station, the individual digital signals are checked for magnitude and power content prior to conversion into the frequency domain by a fast Fourier transform. Previously stored calibration data from each of the receiver stations is combined with the frequency domain data to provide corrected information for correlation to determine the difference in time of arrival of signals from a common emitter station.