A method for determining the position of a roving position receiver in a positioning system comprising at least one reference transmitter at a known location and at least one positioning-unit device (703, 704, 706) at a known location, said method comprising the steps of: each of the at least one reference transmitters generating and transmitting reference positioning signals according to the timebase of said at least one reference transmitter; each of the at least one positioning-unit devices (703, 704, 706): receiving and interpreting signals (705, 707) transmitted by either said at least one reference transmitter or one of said at least one positioning-unit device or both said at least one reference transmitter and said one of said at least one positioning-unit device; determining a reference positioning signal propagation time delay between said at least one reference transmitter or one of said at least one positioning unit device and said positioning-unit device (703, 704, 706); generating and transmitting a unique positioning signal; receiving and interpreting said unique positioning signal; comparing said received and interpreted signals (705, 707) and said unique positioning signal to deduce a frequency difference; adjusting the generation of said unique positioning signal to achieve frequency coherence with said received and interpreted signals (705, 707); comparing said received and interpreted signals (705, 707) and the unique positioning signal to deduce a time difference; adjusting the generation of said unique positioning signal according to the deduced time difference and said reference positioning signal propagation time delay to achieve time coherence with said received and interpreted signals (705, 707); such that said unique positioning signal is chronologically synchronised to said reference positioning signals; and said roving position receiver receiving either: said chronologically synchronised unique positioning signals; or both said reference positioning signals and said chronologically synchronised unique positioning signals; and subsequently calculating its own position without the requirement of differential corrections. each of the at least one reference transmitters generating and transmitting reference positioning signals according to the timebase of said at least one reference transmitter; each of the at least one positioning-unit devices (703, 704, 706): receiving and interpreting signals (705, 707) transmitted by either said at least one reference transmitter or one of said at least one positioning-unit device or both said at least one reference transmitter and said one of said at least one positioning-unit device; determining a reference positioning signal propagation time delay between said at least one reference transmitter or one of said at least one positioning unit device and said positioning-unit device (703, 704, 706); generating and transmitting a unique positioning signal; receiving and interpreting said unique positioning signal; comparing said received and interpreted signals (705, 707) and said unique positioning signal to deduce a frequency difference; adjusting the generation of said unique positioning signal to achieve frequency coherence with said received and interpreted signals (705, 707); comparing said received and interpreted signals (705, 707) and the unique positioning signal to deduce a time difference; adjusting the generation of said unique positioning signal according to the deduced time difference and said reference positioning signal propagation time delay to achieve time coherence with said received and interpreted signals (705, 707); receiving and interpreting signals (705, 707) transmitted by either said at least one reference transmitter or one of said at least one positioning-unit device or both said at least one reference transmitter and said one of said at least one positioning-unit device; determining a reference positioning signal propagation time delay between said at least one reference transmitter or one of said at least one positioning unit device and said positioning-unit device (703, 704, 706); generating and transmitting a unique positioning signal; receiving and interpreting said unique positioning signal; comparing said received and interpreted signals (705, 707) and said unique positioning signal to deduce a frequency difference; adjusting the generation of said unique positioning signal to achieve frequency coherence with said received and interpreted signals (705, 707); comparing said received and interpreted signals (705, 707) and the unique positioning signal to deduce a time difference; adjusting the generation of said unique positioning signal according to the deduced time difference and said reference positioning signal propagation time delay to achieve time coherence with said received and interpreted signals (705, 707); deduced time difference and said reference positioning signal propagation time delay to achieve time coherence with said received and interpreted signals (705, 707); such that said unique positioning signal is chronologically synchronised to said reference positioning signals; and said roving position receiver receiving either: said chronologically synchronised unique positioning signals; or both said reference positioning signals and said chronologically synchronised unique positioning signals; said chronologically synchronised unique positioning signals; or both said reference positioning signals and said chronologically synchronised unique positioning signals; and subsequently calculating its own position without the requirement of differential corrections.