Star Navigation instead of GPS
Thread Starter
Joined: Sep 2000
Posts: 1,605
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From: UK
Star Navigation instead of GPS
Okay this might be a stupid question again but I was reading the SR-71 book by Brian Shul and in it he mentions how the SR-71 navigated by looking at the stars.
What stops us from doing the same?
Wife just walked into the room and seems to think it might be the clouds stopping the system from seeing the stars.......
Thoughts?
What stops us from doing the same?
Wife just walked into the room and seems to think it might be the clouds stopping the system from seeing the stars.......
Thoughts?
Joined: Mar 2002
Posts: 814
Likes: 1
From: Iceland
The Boeing 727 airliner was fitted with a hole in the cockpit roof through which a sextant celestial navigation unit could be fitted. It was an option that could be used if the weather condition would permit.
There is no reason why helicopter pilots would not learn to use a sextant for fun but to use it while flying or include the sextant with all the required books is hardly a good idea
There is no reason why helicopter pilots would not learn to use a sextant for fun but to use it while flying or include the sextant with all the required books is hardly a good idea
Joined: Jul 2006
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From: Ban Don Ling
Aesir .... My opening is always closed when not in use..
Remember navigating Salisbury Plain many a time by star - saved having to get out the old prismatic each time but led us into some curious (avoidable!) locations. SWAG method.
Remember navigating Salisbury Plain many a time by star - saved having to get out the old prismatic each time but led us into some curious (avoidable!) locations. SWAG method.
Joined: Jan 2001
Posts: 1,365
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From: UK
To use stars for navigation, you need to be able to see the stars (or planets). The availability of stars at helicopter altitude in say western Europe would make it considerably less reliable and available than GPS.
Typical astronav accuracy is also MUCH less accurate than GPS.
(Prior to long distance RNAV), for the floaty boys astronav was OK in mid-ocean because an error of 5, 10 or more miles did not matter mid-ocean. And it did not matter too much if you took a couple of days to get a fix in the middle of the Atlantic. If a ship could hit something, they would stick a light on it (those were the days). Astro wouldn't really be good enough for any helicopter ops
Typical astronav accuracy is also MUCH less accurate than GPS.
(Prior to long distance RNAV), for the floaty boys astronav was OK in mid-ocean because an error of 5, 10 or more miles did not matter mid-ocean. And it did not matter too much if you took a couple of days to get a fix in the middle of the Atlantic. If a ship could hit something, they would stick a light on it (those were the days). Astro wouldn't really be good enough for any helicopter ops
Joined: Jan 2009
Posts: 280
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From: around and about
Navigation
OK, Sav, showing my age (again)
In the 70s, Northern Quebec, the Baie James Hydro Project, and transition from one site to another required my pilot to accurately plot our position (and thus course to be followed) using a sextant.
Too far North with a vicious angle of dip, & stack of lodestone about made the compass useless (even an E2B, considered state-of-the-art in an Al II - LOL). 
And navigation from those Quebec maps............. you needed a good imagination. All those lakes, except that the profiles from 1500' bore no resemblance whatsoever to the actuals on the ground........ 
Another time, another (steep) learning curve. Keep the revs up - VFR
In the 70s, Northern Quebec, the Baie James Hydro Project, and transition from one site to another required my pilot to accurately plot our position (and thus course to be followed) using a sextant.
Too far North with a vicious angle of dip, & stack of lodestone about made the compass useless (even an E2B, considered state-of-the-art in an Al II - LOL). And navigation from those Quebec maps............. you needed a good imagination. All those lakes, except that the profiles from 1500' bore no resemblance whatsoever to the actuals on the ground........ Another time, another (steep) learning curve. Keep the revs up - VFR
Joined: Oct 2006
Posts: 5,174
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From: UK
Years ago when I was on 4 jet bombers I would pass the hours practicing astro nav under the watchful eye of the navigators. The result would be three postion lines called a 'cocked hat' and theoretically you would be in the middle.
They used to use my cocked hats as next week's long range navex.
They used to use my cocked hats as next week's long range navex.
Joined: Jul 2003
Posts: 56
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From: Austin, Texas, USA
The SR-71, the B-58, the FB-111, and most spacecraft used astrotrackers for navigation.
An astrotracker is an optical device connected to a computer (analog in the airplanes and older spacecraft) that can see stars even in daylight and automatically calculate continuous multi-star position fixes which are then fed into the craft's navigation computer. This was probably the best available passive nav system available prior to GPS and laser gyros.
The navigator in the SR-71 didn't use a manual sextant.
An astrotracker is an optical device connected to a computer (analog in the airplanes and older spacecraft) that can see stars even in daylight and automatically calculate continuous multi-star position fixes which are then fed into the craft's navigation computer. This was probably the best available passive nav system available prior to GPS and laser gyros.
The navigator in the SR-71 didn't use a manual sextant.
Joined: Jan 2009
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From: no comment ;)
Joined: May 2004
Posts: 917
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From: Tax-land.
Funny, I play navigation trivia with my students once in a while and find out that most of them have no idea what's the difference between a Mercator and a Lambert projection (hell they don't even know what a Lambert is), not to mention what type of projection an everyday sectional is.
Joined: Feb 2004
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From: Lost and Legless somewhere in LaLaLand
There are those in the US military (and presumably those of other countries) who are concerned that GPS is susceptible to jamming and other single-point failures and that other, back-up systems need to be available. Here's an interesting document written by George H Kaplan of the US Naval Observatory on how new technology in celestial navigation techniques could be used to increase accuracy of inertial navigation systems
New Technology for Celestial Navigation
New Technology for Celestial Navigation
Last edited by Phone Wind; 4th January 2013 at 07:32.
