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Boats hit rocks all the time, often snapping off deep keels.

Nov 8, 2010
10,586
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
With xtra-light spectrum camera technology and good computer mapping algorithms, simply pointing a camera at the sky, no matter the weather should beable to yield as precise a location as any satellite technology. Celestial navigation in the Information Age. And, it can't be shut-off or dithered.

- Will (Dragonfly)
Will, this does not make sense. Even if you could null out the motion of the boat, NO technology can see stars though clouds. Or in the daylight.
 
Oct 19, 2017
5,044
O'Day 19 Littleton, NH
NO technology can see stars though clouds. Or in the daylight.
You may be right, I'm not so sure though, with microwave and radio spectrum technology. Don't need stars during the day and boat movement is nothing because you just need a shot with orientation to magnetic north to compare to predictable star position data by universal time and date.

- Will (Dragonfly)
 
Jan 11, 2014
4,150
Sabre 362 113 Fair Haven, NY
You may be right, I'm not so sure though, with microwave and radio spectrum technology. Don't need stars during the day and boat movement is nothing because you just need a shot with orientation to magnetic north to compare to predictable star position data by universal time and date.

- Will (Dragonfly)
Not quite sure I'm understanding you here. The stars are still there during the day, sunlight just floods the sky so they aren't visible. Clouds and fog easily obscure sun, moon, and stars.

While radio telescopes rely on non-visible electromagnetic radiation to locate stars, not sure that is practical on a big boat, much less a small recreational boat. Radio telescopes are receive only, they are not like radar that sends a signal out and then receives the reflection. I think Alpha Centauri is the nearest star to earth (other than the sun) and that is a little over 4 light years away, so it would take 8 to 9 years for the radar signal to reach the star and return. And then you'd need one very big parabolic antenna to capture the signal.
 
Oct 19, 2017
5,044
O'Day 19 Littleton, NH
Not quite sure I'm understanding you here.
I'm referring to receiving only. I could be all wet about what I understand we have the technology to see, but certainly not sonar - like location.

- Will (Dragonfly)
 
Jan 11, 2014
4,150
Sabre 362 113 Fair Haven, NY
I'm referring to receiving only. I could be all wet about what I understand we have the technology to see, but certainly not sonar - like location.
Will, you are correct we have technology to "see" distant stars using electromagnetic radiation. For boaters the issue is size, these suckers are little too big for even our biggest vessels:
Puerto Rico's Arecibo Radio Telescope Suffers Hurricane Damage : The Two-Way : NPR
World's Most Complex Radio Telescope Snaps Stunning 1st Photo of the Cosmos
 
Oct 19, 2017
5,044
O'Day 19 Littleton, NH
you kinda are. That's why I called it out. You're presenting it as fact, and it clearly not.
I certainly don't mind being called out on my BS. However, if the moon or even one bright identifiable star is viewable, we only need to know the angle and declination along with the time to know precisely where we are. The angle is relative to magnetic north, easy enough. The declination is measure by comparing the height of our celestial object to the direction of gravity. The time allows us to match our measurements up to known and predictable data. Compensate for altitude and a computer with that data will always know, in nanoseconds, where it is. None of this requires a steady deck or external devices.

Perhaps my assumption about being able to see through cloud cover is colored by my experiences on the NOAA Web site and what they can see looking down, but I don't think I'm too far out there.

- Will (Dragonfly)
 
Nov 8, 2010
10,586
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
I certainly don't mind being called out on my BS. However, if the moon or even one bright identifiable star is viewable, we only need to know the angle and declination along with the time to know precisely where we are. The angle is relative to magnetic north, easy enough. The declination is measure by comparing the height of our celestial object to the direction of gravity. The time allows us to match our measurements up to known and predictable data. Compensate for altitude and a computer with that data will always know, in nanoseconds, where it is. None of this requires a steady deck or external devices.

Perhaps my assumption about being able to see through cloud cover is colored by my experiences on the NOAA Web site and what they can see looking down, but I don't think I'm too far out there.

- Will (Dragonfly)
The devil is always in the details. You are talking about making an electronic sextant. But how on earth (pun intended) are you going to measure any angle with high accuracy and reliably? And if you don't know where you are to start, how will your machine recognize where to look at in the sky, a bit of a catch-22? Assuming it can see it day and night, clear or cloudy.

Even if you could solve that, you need to makes it the size of a pack of smokes, battery powered, and for 30 dollars.

Oh, we see 'down' via thermal imaging. The surface of the earth has huge (relatively speaking) variances in temp over reasonable angles of resolution. We can't look into the sky and pick out a 'warm' pinprick of light. There is no heat.
 
Aug 1, 2011
3,490
Catalina 270 Wabamun - on the orange ball
Shades of Vince. It slices, it dices and if you call in the next 2 minutes, cuz we can't do this all day, we'll double the order.
 
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Jun 3, 2004
234
Hunter 336 Pensacola
The declination is measure by comparing the height of our celestial object to the direction of gravity.
I think determining the direction of gravity alone will induce more error than any satellite based navigation system. In order to achieve 3' accuracy, I believe you need to resolve the angle to about .03 arc seconds. Given that the earth is not uniform in density (the local gravity vector is deflected from true vertical) and you are measuring from an accelerated frame of reference (the rotating earth), I don't think this level of accuracy is possible.
 
Nov 8, 2010
10,586
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
My worst sunburn has been on an overcast day.

- Will (Dragonfly)
So did someone else, 1000 miles away. And you still have to find it, and sus it's angle. With everything moving. One minute of a degree of error in reading is a nautical mile of ground error. Even them, at best you are describing a solution that works on average 12 hours a day.

I'm going to stop replying to this part of this thread, its clear you're not getting the bigger picture, or just screwing around. Ether way its a waste of my time.
 
Jan 11, 2014
4,150
Sabre 362 113 Fair Haven, NY
[
My worst sunburn has been on an overcast day.

- Will (Dragonfly)
The operative word is day. UV light can penetrate clouds. I've never heard of anyone getting starburned or moonburned.

Determining one's approximate position on earth when out of sight of land does require measuring angles, i.e., the angle above the horizon at which the celestial body lies a specific time. (Jack Lagan's book, The Barefoot Navigator, describes several ways ancient navigators established their latitude. It is an interesting read.) The rub is in the details, how do you precisely measure that angle?

Then there is the problem of time. One that vexed mariners for centuries. It is possible to establish latitude with limited reference to time, but it is tedious and requires being in a fixed position, i.e., on land. (See David Barrie's book, Sextant, for the stories of early explorers and how they tried to map the world.)

You may also want to read Dava Sobel's Longitude, which examines the problems of developing an accurate time piece, necessary to measure time at sea.

Finally, here's a photo of my wife who precisely knew her longitude at 00.00.00 degrees (we're not so certain about the longitude):
DSC_1865.jpg
 
Oct 19, 2017
5,044
O'Day 19 Littleton, NH
I'm going to stop replying to this part of this thread, its clear you're not getting the bigger picture, or just screwing around.
Jackdaw, I made a bold statement, you called me out on it. I explained myself, you and others pointed to errors in my knowledge-base, I argued back, corrected an assumption based on your information and elaborated on my idea. I remain sceptical about the impossibilities of my thoughts, but I respect your position. If we have the technology to measure a 5mm change in a distant planet's orbit, I can't imagine we can't put instruments on a boat that can find its position within feet of a dangerous and known rock without satellite help.
There is, of course, a point at which this discussion needs to wind down and I think you are wise to be sensitive to it at this time. Another of my many failing is my inability to recognise those times before it is too late.
I hope you know I hold your opinions in high regard. I just don't agree with you on this. :meh:

- Will (Dragonfly)
 
Nov 8, 2010
10,586
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
Jackdaw, I made a bold statement, you called me out on it. I explained myself, you and others pointed to errors in my knowledge-base, I argued back, corrected an assumption based on your information and elaborated on my idea. I remain sceptical about the impossibilities of my thoughts, but I respect your position. If we have the technology to measure a 5mm change in a distant planet's orbit, I can't imagine we can't put instruments on a boat that can find its position within feet of a dangerous and known rock without satellite help.
There is, of course, a point at which this discussion needs to wind down and I think you are wise to be sensitive to it at this time. Another of my many failing is my inability to recognise those times before it is too late.
I hope you know I hold your opinions in high regard. I just don't agree with you on this. :meh:

- Will (Dragonfly)
OK against my better judgment I'll try again.

You say If we have the technology to measure a 5mm change in a distant planet's orbit. Maybe if you have A FIXED KNOWN LOCATION. Like a huge radio telescope bolted to bedrock and at a fixed known lat/long. Both are untrue on a boat, and it creates a catch-22. The whole premise is faulty.

My bigger issue this. Both my father and granddad were scientists, and they taught me to always know the difference between a fact, a theory, and an opinion. I think about that in everything I write and say. Too often statements are made as truths when they aren't even decent theorys, just opinions. Read by someone with less understating on the matter, it creates untruths that can be spread.

Per my post in the Mac forum, I'm pretty chill when it comes to differences of opinion. But I'm a very critical thinker, and anything less than truth passed off as such will get my attention anywhere.
 
Jan 11, 2014
4,150
Sabre 362 113 Fair Haven, NY
As the late Senator Moynihan once said, "Sir, you are entitled to your own opinions, but not your own facts."

To drift off topic, but then this whole thread has sort of drifted off topic, the teaching and valuing of science, the scientific method, and critical evaluation of ideas has been devalued over the past couple of decades. Concurrently we have become increasingly dependent on the very products of science and technology, without understanding the underlying principles and the limitations. As a result we end up with all kinds of untoward events. Anyone remember Vestas from the last VOR? A well known reef, state of the art navigation technology, some of world's best sailors and navigators, and still the crew ran a multi-million dollar boat up on a reef.
 
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Mar 16, 2010
5,943
Beneteau 411 Oceanis Annapolis
On this same blog, here's an interesting piece on one way to design the keel to hull attachment, to better handle a grounding in a boat with a high performance keel.

https://stephenswaring.com/marine-engineering-for-ups-why-my-keel-does-not-fall-off/

GINGER's keel was designed with a grounding in mind. Pretty boat that looks like fun to sail! This low boat is 50 feet long.
You know that is some amazing engineering, and a beautiful boat but I feel quite certain that if you ran that thing up on a Maine ledge at speed you are still going to be subject to Newton’s 3rd Law - and will be launch the keel out through the pilot house!

I have a similar shaped keel and it does a pretty good job of shedding warps and lines...right back to the propeller and rudder. Might be more cost effective to carry a young crew member with good lungs and a sharp knife, that was my dad’s method.:p
 
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Nov 8, 2010
10,586
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
You know that is some amazing engineering, and a beautiful boat but I feel quite certain that if you ran that thing up on a Maine ledge at speed you are still going to be subject to Newton’s 3rd Law - and will be launch the keel out through the pilot house!
Indeed. And while it introduces complexity and cost, this is one of the big advantages of a lifting keel. Modern ones have built-in hydraulic fuses that allow the keep to swing back on solid impact, saving the hull from damage.