Genesis of Loran Augmented Satellite Navigation

摘要

The Iotron Corporation was formed specifically to pioneer the development and production of the world's first fully automatic self-plotting radar for merchant ship collision avoidance. Transit satellite navigation was added for worldwide navigation and route planning. Loran C was subsequently added for SatNav augmentation to continuously display the International Maritime Organization (IMO) designated traffic separation lanes accurately on the radar plan position indicator (PPI). Transit required an accurate ship's speed-over-the-ground during the satellite data transmission, and dead reckoning using conventional ship's through-the-water speed logs was not adequate when sailing near land in up to 5-knot currents that exist where the traffic lanes were mandated. Iotron used a super tanker's Doppler docking system's ground speed measurements to obtain the most accurate Transit satellite fixes. Then, in order to maintain this accuracy in between fixes for continuously displaying the charted traffic separation lanes, the integrated concept used the Transit fixes to periodically update Loran C's hyperbolic navigation. Although Loran C's 2drms accuracy alone was only 460m, Iotron's proprietary innovation was the first to utilize Loran C's (18 to 90m) repeatable accuracy to complement Transit satellite navigation's fix updates for maintaining < 100m continuous accuracy even in currents. This unpublished maritime Transit augmentation exploited Loran C's continuous repeatable accuracy to provide the nearly 100-meter accuracy that equaled GPS for 20 years until Selective Availability (SA) was removed. Iotron not only pioneered "Hands off anti-collision Automatic Radar Plotting Aids, later designated by the IMO as an automatic acquisition ARPA, but also accurately superimposed charted sea-lanes and planned route lines on the PPI. The anti-collision equipment was successfully competed against Raytheon, Sperry, IBM and foreign companies by installing DIGIPLOTS on over 500 ships out of the 3000 total that had been sold worldwide. In addition, Transit satellite navigation augmented by Loran C (or Decca Navigator) was fitted on 34 super tankers.