Celestial navigation practices


Dave Gittins

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Boxhall was talking about the methods that gave latitude and longitude purely by calculation, with no plotting on a plotting chart. You observed stars lying roughly east or west for longitude and stars lying north or south for latitude. The Mark St-Hillaire method was only required for Extra Masters and old hands regarded it with suspicion, because of the plotting and possible errors. The old methods made a comeback in the 1980s, using programmable calculators that also contained data about the celestial bodies. I assume the work can now be done on a computer.
 

Jim Currie

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Hello Dave.

You might also add that a calculated Latitude and a calculated Longitude are both position lines upon which the vessel is located at a specific point on the line.

They would have used position lines way back then, and would have used either squared paper or an Aqino's Protractor much like the the one shown here if they wished to do a plot.
Aquino 2019-12-07 001.jpg


These were being taught for Mate and Master s late as the 1960s. Although by then, the Marc St Hilair method was the method of preference.
 
Mar 22, 2003
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If your GPS breaks down then what!
Sorry Mike, but the 21st century is here to stay. These days you can use even use a cellphone to get your lat/lon coordinates from the GPS satellites, and then you just have to plot it on a chart. There are some more expensive marine GPS units that also could use the GLONASS system as a backup, which is the Russian version of GPS, in the remote case of the US maintained GPS system failure.
 
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Doug Criner

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I understand that the U.S. Navy is recently teaching a smattering of celestial navigation. (I wonder who teaches it?) But what to do when GPS shoots craps? Dead reckoning, visual bearings if near land, and, of course, as a last resort, celestial navigation. I once got a bridge tour on a cruise ship. There was a continuous GPS plot running that I peeked at. It showed that the ship had sailed straight across a island. When I asked about that, they just shrugged and said GPS wasn't perfect. Maybe it was just the chart that was imperfectly imbedded into the software.
 

Mark Baber

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About 15 (maybe more) years ago, my father-in-law navigated most of a trip from San Diego to Honolulu by the stars after rain knocked out his GPS (or whatever the system of the day was) on the second day out.
 
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GPS with augmentation systems has become critical in aviation during instrument flying conditions at many airports. See here: Satellite Navigation — GPS/WAAS Approaches
When I was actively flying GPS was just starting to be used by the general aviation community but none of it was certified for landings. It was really nice for navigation purposes though. It was mainly VOR for me and IFR ( I Follow the Road). But GPS is still pretty cool especially after they took out the built in error. I have a hand held GPS unit but to be honest I mostly use it now to verify the speedodmeters on the toys I rebuild. Its very accurate for that.
 
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I understand that the U.S. Navy is recently teaching a smattering of celestial navigation. (I wonder who teaches it?) But what to do when GPS shoots craps? Dead reckoning, visual bearings if near land, and, of course, as a last resort, celestial navigation. I once got a bridge tour on a cruise ship. There was a continuous GPS plot running that I peeked at. It showed that the ship had sailed straight across a island. When I asked about that, they just shrugged and said GPS wasn't perfect. Maybe it was just the chart that was imperfectly imbedded into the software.
I dont know but I think it would be a very good idea. If the big one ever breaks out GPS will be targeted and taken out. It could the weapons community. I know the Trident SLBM's use stellar compensated inertial guidance. Buts thats done by onboard computer/gyro's and optics. But thats more of a geek thing than some watch officer on the bridge. They should learn the old/different ways in case they ever needed them. I don't see a down side to them learning it.
 

Mike Spooner

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Array for modern technology of satellites for GPS. What if the satellites breaks down! Where the old technology used for hundred of years might come quite handy. I don't know if sexton are still standard equipment on ships today?
 

Jim Currie

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Russia and China (and presumably the US) are developing aircraft and electronic systems which can disable satellites. Global warming issues are changing our ideas of power production and consumption. The world as we know it is constantly changing. Beware complacency.
 
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Mar 22, 2003
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When I was actively flying GPS was just starting to be used by the general aviation community but none of it was certified for landings. It was really nice for navigation purposes though.
The same with me. My flying club started to equip our planes with them. I always considered it as a nice to have backup, not a primary navigational device. Part of the fun of flying, at least for me, was in the flight planning, which included adding in corrections for forecasted winds aloft, and then correcting for actual winds aloft during the flight itself. I do miss those cross-country flights over NJ and PA back in the good old days, and flying up the Hudson river at 1000 ft with the NY skyline along your starboard side. That was before 9/11.
 

Jim Currie

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I started navigating using exactly the same methods as were used in 1912.
In the 80's I presided over the movement of A Sedco Semi Submersible drilling barge from Bergen out to a 20 feet single point moored buoy in the middle of the North sea. It was the first time it was done entirely by computer hooked to the Azimuth drives for propulsion and to a portable GPS system in a suitcase which was accurate to within 10 yards. We did not have differential system. We hit the target right on the money. Thereafter, we deployed 27 anchors using the "suitcase " in the control room and a VHF link to the anchor handler. Great fun!
By 2004, I had an integrated GPS and sonar that could identify fish by species on my little harbour Master's launch/ Having said all that. I can still find out where I am at sea with my sextant , my very accurate wrist watch a set of old Tables and an Almanac.
I count myself so very lucky to have lived in these times.
 
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Doug Criner

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Pull out your cracker jack box compass...find north then head east or west. You'll run into land sooner or later.
Ha! If GPS satelites shoot craps or are knocked out by an enemy missile, plot radar ranges and bearings of any nearby terrestrial features. If there are no terrestrial features within radar, then go with dead reckoning from last known position.
 

Doug Criner

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Fifty years ago, I had some experience on ballistic missile submarines - but only the propulsion plant (nothing to do with the missiles). However, I picked up some info through scuttlebutt, that even if it was then correct, is probably long obsolete. This was before the advent of GPS. The ships themselves had intertial guidance systems that allowed tracking their own position without any reference to the outside world, including even GPS, if such had existed at the time. The ship's position at the time of ICBM launch was loaded into the missile - but targeting required a bit more accuracy. Supposedly, when the missile reached the stratosphere, or whatever, the missile activated a celestial sighting gadget (like a sextant?) and took enough star sights to get a very accurate fix and to fine tune the final targeting. Wonderful.

But, Yes, in the event of a real nuclear war, it might have been advisable for the submarine to remain submerged until after the war ended ;)
 
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From what I understand the SLBM's actually just sight on a single star to correct for the lessor accuracy of moving launch platform data. Thats at least for the Trident II's. Which is what the brits use also. Yes I agree about staying submerged. Head for the southern hemisphere and find a nice tropical island somewhere. Back in the day the rumor was there were subs that they called "long trigger" boats. Their job was to lay under the ice for a month or 2 after the conflict and wait for the commies to crawl out of their holes and then whack them again. The cold war was an interesting and sometimes frightening time to grow up in. But at least we knew who the bad guys were. Now...?

P.S. This being a Titanic board I dont think it would have made any differance to Titanic if they knew down to the square inch what their exact position was when they sank. It was the cold water that killed most. They didn't need all the advanced technology of today to avoid the accident. Just better command decisions would have done the job.
 

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