Accurate location system using transponded and correlated LORAN signals

A position location system for locating the position of a tracked unit comprising:

• first and second means for transmitting first and second signals at a first frequency, respectively, said first means and said second means being located remotely from each other;
• master means for receiving and storing said first and second signals from said first and second transmitting means, said master means being located remotely from said first and second means for transmitting;
• second means for receiving said first and second signals from said first and second transmitting means, said second means being located at said tracked unit, said second receiving means converting said first and second signals to third and fourth signals at a second frequency and transponding said third and fourth signals to said master receiving means, said master receiving means converting said third and fourth signals to said first frequency;
• and
• correlation detection means located within said master receiving means for cross-correlating said transponded third and fourth signals with said stored first and second signals for determining the additional times of flight (.tau.) of said third and fourth signals transponded to said master receiving means wherein the locus of points of constant (.tau.) form first and second ellipses associated with each of said first and second signals, respectively, with one of a plurality of intersections of said ellipses defining the position of said tracked unit.