Is GPS Obsoleting the Sextant?

[sailaway21]

In any event, I see little to dissuade me from thinking that there are numerous national security issues that could and would result in a shut-down of the GPS system. I'll go out on a limb and say that they'd probably be sporadic but I'm sure that there are many scenarios that the Pentagon has played out in simulation. And in an ever-changing technological world, denying the enemy the use of technology is often better than having it your self.

On the issue of being targeted at sea I'll take the chance that they can't locate one fast ship with no lights or radio emissions. And the North Atlantic does interesting things to wakes and thermal imaging which might be fine in more restricted waters or smaller search areas. My only contention on such technologies though is that they tend to be self-cancelling. Once the enemy had sonar the utlity of active sonar decreased immeasurably. If your enemy is technologically deficient you use technology to beat him. If your enemy is technologically advanced you deny him the technology to beat him.

[Plumper]

Originally Posted by sailaway21

In any event, I see little to dissuade me from thinking that there are numerous national security issues that could and would result in a shut-down of the GPS system. I'll go out on a limb and say that they'd probably be sporadic but I'm sure that there are many scenarios that the Pentagon has played out in simulation. And in an ever-changing technological world, denying the enemy the use of technology is often better than having it your self.

On the issue of being targeted at sea I'll take the chance that they can't locate one fast ship with no lights or radio emissions. And the North Atlantic does interesting things to wakes and thermal imaging which might be fine in more restricted waters or smaller search areas. My only contention on such technologies though is that they tend to be self-cancelling. Once the enemy had sonar the utlity of active sonar decreased immeasurably. If your enemy is technologically deficient you use technology to beat him. If your enemy is technologically advanced you deny him the technology to beat him.

It is unlikely that the GPS system would be shut down entirely. A more likely situation is that the operators would introduce error again so that it could not be used for targeting wthout the code. It would still be better than sextants. In the world climate that calls for that action it is unlikely we would be lallygagging and out sailing anyway. Much of the world's commercial transport is now so reliant on GPS that to shut it down would unnecessarily endanger many lives. It is more probable that the bad guys (whoever they are) would deny GPS service in some areas. That would hardly affect yachties unless you were yachting in a war zone.

All in all, I think you can pretty much rely on GPS more than some wannabe with a sky wrench.

[JiffyLube]

Originally Posted by Plumper

In the world climate that calls for that action it is unlikely we would be lallygagging and out sailing anyway.

If it ever got to that, I'd be trying to get my last good sail in...lol

[Valiente]

Originally Posted by tjaldur

Thank you. Somehow I doubt that I ever will rename my ship to "Oystercracker".

I think people who speak English or Norwegian would support that decision....

[sailaway21]

Originally Posted by Plumper

It is unlikely that the GPS system would be shut down entirely. A more likely situation is that the operators would introduce error again so that it could not be used for targeting wthout the code. It would still be better than sextants. In the world climate that calls for that action it is unlikely we would be lallygagging and out sailing anyway. Much of the world's commercial transport is now so reliant on GPS that to shut it down would unnecessarily endanger many lives. It is more probable that the bad guys (whoever they are) would deny GPS service in some areas. That would hardly affect yachties unless you were yachting in a war zone.

All in all, I think you can pretty much rely on GPS more than some wannabe with a sky wrench.

None of the commercial ships I spent twenty years sailing in. It may come as a shock to some but ships moved quite well before all of this electronic gear. Not as efficiently but about as safely. Radar has probably caused as many collisions as it's prevented. Of course, if the harbor is fogged in you don't sail until the fog lifts. It doens't mean you don't sail. And, btw, there's very little GPS knowledge required to pass the Third Mate-Oceans exam but you'd best be up on your celestial. A third mate showing up on a ship without a sextant box under arm is about as welcome as a plumber without a wrench. But then, we take our navigation seriously in the merchant marine.

[tjaldur]

hellosailor:

Of course I am familiar with the ravens of Odin, named Hugin and Munin (thought and memory), but they were not navigational aids, rather Odins source of intelligence to keep track everything that happened in the world.

Hugin and Munin - Wikipedia, the free encyclopedia

I think we all can agree that the odds for GPS breakdown are comfortably small. I believe that the odds for electric breakdown, at least in my ship, is considerably greater. I can not 100% guarantee that I will never experience electric breakdown again. It even happened last year, in the ARC race between the Canary Islands and St. Lucia, that one of the participants lost current and needed to use the sextant.

It is well known that salt water is very hostile to electronic equipment and that current failure is to be expected conserning electronic equipment. And I fail to see the disadvantage of being indepent of electronic devices for navigation.

[hellosailor]

"rather Odins source of intelligence to keep track everything that happened in the world." Isn't navigation just a matter of good intelligence as to what lies about one?

Actually I'd heard that Vikings navigated with a host of "lost" aids, including sunstones (naturally polarizing crystal, allowing the sun's position to be seen eventhrough cloud cover) and ravens. Apparently if you take a raven to sea and loose it, it will head for land--even if you can't see where the land is, you can follow the raven. Something like Noah's doves.

Plumper, don't foget that the US has *two* GPS systems, not just one. There are only one set of satellites, but there are two signals being broadcast from them. The civilian signal, which can be diddled to reduce accuracy, and the fully encrypted military signal--that civilian receivers cannot work with at all. US citizens are, or at least were, allowed to apply for a military-grade GPS but that all changed with the first Gulf War, when there weren't enough GPS units being made to fillthe need, and soldiers were writing home and asking their folks to "send me a GPS" so they could navigate in the desert.

I don't recall who you have to apply to for the military-grade unit but expect that you'll have to show good cause, and pass a security background check.

[Plumper]

Originally Posted by hellosailor

"rather Odins source of intelligence to keep track everything that happened in the world." Isn't navigation just a matter of good intelligence as to what lies about one?

Actually I'd heard that Vikings navigated with a host of "lost" aids, including sunstones (naturally polarizing crystal, allowing the sun's position to be seen eventhrough cloud cover) and ravens. Apparently if you take a raven to sea and loose it, it will head for land--even if you can't see where the land is, you can follow the raven. Something like Noah's doves.

Plumper, don't foget that the US has *two* GPS systems, not just one. There are only one set of satellites, but there are two signals being broadcast from them. The civilian signal, which can be diddled to reduce accuracy, and the fully encrypted military signal--that civilian receivers cannot work with at all. US citizens are, or at least were, allowed to apply for a military-grade GPS but that all changed with the first Gulf War, when there weren't enough GPS units being made to fillthe need, and soldiers were writing home and asking their folks to "send me a GPS" so they could navigate in the desert.

I don't recall who you have to apply to for the military-grade unit but expect that you'll have to show good cause, and pass a security background check.

It wasn't two GPS systems, it was one with an encrypted signal and a corresponding key in mil grade receivers. Now the encryption is lifted, the mil signal is the same. You are right though, they can re-encrypt it at will. None of that matters now with DGPS (differential) because with a known point on the ground you can calculate the error and send the correction to any DGPS capable receiver. That is essentially why the got rid of the encryption. It didn't do anything. Any signal error would have to be constantly changing in order to screw up DGPS. The difference between the two receivers was only about 100 yards anyway. Good enough for me with the lesser accuracy. Still beats a sextant. My sky wrench fixes were never better than a couple miles.

[tjaldur]

hellosailor:

there is indeed a story about one man, Raven-Floki, that used ravens to find Iceland. Still that is a story about a man who trained and tamed ravens. Not an ordinary means of navigation.

Iceland was first found by Ingolfur Arnarson by means of his high seat pillars.

Settlement of Iceland - Wikipedia, the free encyclopedia

Odin on the other hand used to travel on land with his horse Sleipnir that had 8 legs and was the fastest horse in the world.

Sleipnir - Wikipedia, the free encyclopedia

There is no doubt that the accuracy of the GPS far supersedes the sextant. Even the best navigator under the best of conditions must calculate an error margin of at least 1 NM.

My own personal error margin with a sextant is closer to 5 NM. However the question whether the sextant is obsolete or not is, in my opinion, not a question of accuracy, but a question of the possibilities of GPS failure. As I see it there are at least three different possibilities of GPS failure.

1) Political, that is the owner of the GPS-system may find it prudent, for some reason, to close the signals for leisure boats.

2) Physical, that includes solar flares. A phenomena we do not entirely know as the activity of these flares seems to be stronger now than they have been the last 8 000 years. The activity of these flares will peak in 2011, so time will show.

3) Electric failure on board, by far the most probable failure.

The sum of there possibilities has led me to the conclusion that I continue to buy the Nautical Almanac and brush the dust off my sextant from time to time. As well as I always use dead reckoning on papercharts together with the use of electronic navigation with GPS and a portable computer. Most accidents starts with the conviction that: "This will not happen to me".