My career was in Marine Seismic Exploration, used to use the Racal Pulse 8 station nav chain off Malasia for long range navigation, ARGO ( Automatic Ranging Grid Overlay ) was used in the Arctic, the medium range radio nav was Hyfix and Hyfix-6 and Maxiran.. I can well remember the joys of checking calibration by cutting baselines and undertaking calibration 3 way fix's.. Then along came GPS, our parent company was Texas Instruments who was one of the US electronic contractors asked by the US Gov to develop the system.. the first reciever onboard we used was about 2ft by 2ft in size with a large calculator size hand set to interface to it.. Because we were involved in surveys all over the globe and many miles from land we were ideal test guinea pigs for GPS.. The early initial system used 3 SV's ( space vehicles ) and what was known at the time as an atomic clock ( now known as a cesium standard ) onboard, ohh the joy when we could lock onto 3 sats for an hour and navigate using GPS before going back onto long range radio nav. The only hiccup was that the military used to muck around with the positions of the SV's, so I had a direct tel number to white sands missile base to call via our Marisat system to check that they were not fine tuning and changing the SV orbits..
GPS nav then changed everything offshore and made life a lot easier to navigate, until they changed the quality of the position fix in the Gulf war, to obtain our degree of navigation precision, we then used a system called differential GPS, which was a mix of GPS positioning integrated with radio navigation from known positions of land based radio stations.. Those were the days..
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