The return of celestial navigation…?


                             Dennis O'Neill            Digital Sextant (Credit: Lee Young SND)

With GPS interference on the rise, navies and the shipping industry are reassessing the benefits of the most successful maritime navigational tool of all time — the humble sextant. 

The Global Positioning System (GPS), owned and operated by the US government, is under increasing threat from criminal gangs, sophisticated state actors including China, Iran and North Korea, and even potentially catastrophic cosmic rays emitted by solar flares.  

Other global navigation satellite systems exist — Russia’s Glonass, Europe’s Galileo and China’s BeiDou — but they all rely on exactly the same GNSS (the Global Navigation Satellite System) satellite constellation as GPS, thereby sharing the very same vulnerabilities. 

In anticipation of satellite navigation disappearing, suddenly and totally, industry and navies around the world have begun preparing for a return to using the traditional navigational tool that ruled the waves, globally, for more than two hundred years — the celestial sextant. 

Celestial navigation can, however, be a complicated business for even the most experienced of operators — a challenge which led to the US Navy dropping it from its curriculum in 1998 only to reinstate it again in 2015 following a series of damaging cyber-attacks on the GNSS.


Digital sextant
A promising solution could lie with the world’s first digital sextant — the Korean-built DS-10. 

Based on the well-respected Chinese-built Astra IIIB sextant, the DS-10 allows a celestial navigator to calculate their position almost instantly with no need for sight reduction tables, nautical almanacs or having to run through long and elaborate mathematical calculations. 

The unit is already so successful that navies across Asia have begun using it aboard their vessels, with the South Korean navy now mandating its use on all of its vessels. 

“The soul of the unit is the index bar, used to calculate the angles, which connects directly with the digital processor,” explains Hungarian ex-naval officer Istvan Kopar, who has circumnavigated the globe by yacht three times, using only a sextant for navigation.  

“You take a traditional sighting, by measuring the elevation of a celestial body above the horizon, then push a button on the handle to record the exact measurement of the angle and the timing. Although it doesn’t use a GPS, you still get a really quick calculation, within seconds, as long as you’re able to do the sighting with at least one celestial body.” 

“For me, the DS-10 is the ultimate back-up because it’s a stand-alone unit that doesn’t rely on any outside power source. Following an emergency, such as a lightning strike, you will be able to use it with complete confidence to calculate your position accurately in seconds.” 


Enhanced signals

Other back-up technology being prepared for a total loss of GPS includes a new digital version of Long Range Navigation (Loran). Developed in World War II to guide allied ships across the Atlantic using land-based transmitters to broadcast radio signals, the new version — eLoran — offers locational accuracy to within 10m (32ft) while using more advanced transmitters and receivers that are able to emit signals so powerful they are difficult to jam.




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