True
Virgins (Variation)
Make (Magnetic)
Dull (Deviation)
Companions (Compass)
Add Whiskey (Add West)

This message has been edited. Last edited by: CaptainMike,

The shift in magnetic north may have been caused by the sudden (in geologic terms) left flip flopping to the polar opposite on the wall issue. When most of the media reports followed the effect on millions of mindless minions could then be measured and if allowed to continue would make our world less safe. This is only possible because the densest known material currently on earth is our liberal left. Hell, they make my mind spin....

quote:

Originally posted by maladat:

quote:

Originally posted by eltonr:

it would be interesting how this is being handled by current GPS technology. or if the old Loran system would be affected by shift in magnetic fields?


tymll

Loran operated on essentially the same principles as modern GPS.

Both systems use stations transmitting synchronized signals. The user receives these signals, which are no longer synchronized because he is different distances from the different stations, so the signals take different amounts of time to reach him. By precisely measuring the offsets between the signals and referring to the known locations of the stations, the user can triangulate his position. It's just that Loran used ground stations and GPS uses satellites, and GPS is a lot newer so the stations are better synchronized and the users can measure the offsets more precisely.

In either case, magnetic north has nothing to do with the process.

They are more expensive than magnetic compasses, but many boats and I expect virtually all ships have gyrocompasses on board. A gyrocompass is a fascinating instrument that uses gyroscopic precession to automatically align itself with the axis of the rotation of the earth (true north). No dependence on the Earth's magnetic field at all.

Modern sensor technology has actually advanced to the point that now there are "gyrocompasses" that don't actually have gyroscopes in them - they can measure the movement of the instrument with enough precision that they can simply measure the rotation of the earth directly (yes, even in a moving vessel!) and determine the axis of rotation.

As an old USCG LORAN A and C tech I'm impressed with your explanation. I couldn't have done it better.

quote:

Originally posted by CaptainMike:
True
Virgins (Variation)
Make (Magnetic)
Dull (Deviation)
Companions (Compass)
Add Whiskey (Add West)

Learned it a couple of different ways back at USCGA in 1978:

Timid (True)
Virgins (Variation)
Make (Magnetic)
Dull (Deviation)
Companions (Compass)
At (add)
Weddings (West)

Going the other way:

Can (Compass)
Dead (Deviation)
Men (Magnetic)
Vote (Variation)
Twice (True)
At (add)
Elections (East)

Amazing how some stuff can stay stuck in the back of your brain for such a long time.

As interesting as the subject is - they have to weave global warming into the article, which is different from global cooling. Yawn

This is happening because I don't sort my trash, isn't it?

The North Star changes over time, both short and long-term. Polaris hasn't always been the North Star, and will not be the North Star in the future.
Amazing how little consequence humans have in the big picture. Of course the magnetic pole changing, speeding up changing, etc. is the fault of our human actions especially over the past few years!

https://earthsky.org/astronomy.../north-star-movement

quote:

Originally posted by cwelch:

quote:

Originally posted by maladat:

quote:

Originally posted by eltonr:

it would be interesting how this is being handled by current GPS technology. or if the old Loran system would be affected by shift in magnetic fields?


tymll

Loran operated on essentially the same principles as modern GPS.

Both systems use stations transmitting synchronized signals. The user receives these signals, which are no longer synchronized because he is different distances from the different stations, so the signals take different amounts of time to reach him. By precisely measuring the offsets between the signals and referring to the known locations of the stations, the user can triangulate his position. It's just that Loran used ground stations and GPS uses satellites, and GPS is a lot newer so the stations are better synchronized and the users can measure the offsets more precisely.

In either case, magnetic north has nothing to do with the process.

They are more expensive than magnetic compasses, but many boats and I expect virtually all ships have gyrocompasses on board. A gyrocompass is a fascinating instrument that uses gyroscopic precession to automatically align itself with the axis of the rotation of the earth (true north). No dependence on the Earth's magnetic field at all.

Modern sensor technology has actually advanced to the point that now there are "gyrocompasses" that don't actually have gyroscopes in them - they can measure the movement of the instrument with enough precision that they can simply measure the rotation of the earth directly (yes, even in a moving vessel!) and determine the axis of rotation.

As an old USCG LORAN A and C tech I'm impressed with your explanation. I couldn't have done it better.

the loran on my boat when I bought her, was off about a mile SE of my actual location. but I was inland on the neuse river, and that was suppose to interfere with the loran signal that it received. upgraded to GPS, hand held at first, chart plotter now.

it was my understanding that fishermen liked the loran because accuracy was within 6' of "marks" plotted. GPS has and accuracy of 10 meters now. 30'?

loran was redundant especially with current GPS technology.

ymmv

So my compass acts up. Big deal. Whats the worst that can happen?

quote:

Originally posted by bubbatime:
So my compass acts up. Big deal. Whats the worst that can happen?

You get too close to the edge, and fall off.

quote:

Originally posted by eltonr:

quote:

Originally posted by cwelch:

quote:

Originally posted by maladat:

quote:

Originally posted by eltonr:

it would be interesting how this is being handled by current GPS technology. or if the old Loran system would be affected by shift in magnetic fields?


tymll

Loran operated on essentially the same principles as modern GPS.

Both systems use stations transmitting synchronized signals. The user receives these signals, which are no longer synchronized because he is different distances from the different stations, so the signals take different amounts of time to reach him. By precisely measuring the offsets between the signals and referring to the known locations of the stations, the user can triangulate his position. It's just that Loran used ground stations and GPS uses satellites, and GPS is a lot newer so the stations are better synchronized and the users can measure the offsets more precisely.

In either case, magnetic north has nothing to do with the process.

They are more expensive than magnetic compasses, but many boats and I expect virtually all ships have gyrocompasses on board. A gyrocompass is a fascinating instrument that uses gyroscopic precession to automatically align itself with the axis of the rotation of the earth (true north). No dependence on the Earth's magnetic field at all.

Modern sensor technology has actually advanced to the point that now there are "gyrocompasses" that don't actually have gyroscopes in them - they can measure the movement of the instrument with enough precision that they can simply measure the rotation of the earth directly (yes, even in a moving vessel!) and determine the axis of rotation.

As an old USCG LORAN A and C tech I'm impressed with your explanation. I couldn't have done it better.

the loran on my boat when I bought her, was off about a mile SE of my actual location. but I was inland on the neuse river, and that was suppose to interfere with the loran signal that it received. upgraded to GPS, hand held at first, chart plotter now.

it was my understanding that fishermen liked the loran because accuracy was within 6' of "marks" plotted. GPS has and accuracy of 10 meters now. 30'?

loran was redundant especially with current GPS technology.

ymmv

Loran used low frequency transmitters. The benefit is that low frequency signals sort of follow the curvature of the earth. Between the height of the towers, power of the transmitters, and low frequency of the transmission, there was Loran coverage hundreds of miles offshore.

The Coast Guard maintains coastal VHF voice stations on similarly tall towers, and coverage there is more like 25 miles.

I used Loran a little as a kid but wasn't up on all the details. Wikipedia says Loran-C (the last, best performance version) has absolute accuracy (difference between actual and calculated position) of .1-.25 miles and repeatability (if you try to go back to the same calculated position, how close do you get) of 60-300 feet.

Pre-2000, there were intentionally-introduced errors in the GPS signals that limited accuracy of standard GPS receivers to about 300 feet.

Inshore, accuracy could be TERRIBLE with Loran, because the low frequency signal bounces off of and/or travels around ground features, buildings, etc, which results in a signal path difference that may be significantly longer than the "straight line" (actually following the curvature of the earth) distance.

Basic GPS devices today should almost always be within 10 meters, and usually within 3 or 4. There are apparently new consumer GPS devices using a newly-deployed signal standard that are accurate to about 1 foot (this seems to be new within the last year). Special high precision GPS devices, using several different approaches, have been available for decades that can achieve accuracy of an inch or less.

The GPS satellites also transmit higher frequency encrypted signals used by the government and military for higher-precision positioning than the previously available unencrypted civilian signals (the details are classified, so I don't know how the accuracy of devices using the encrypted signal compare to the new high precision civilian signal).

I have a friend that 20+ years ago was working for a company that built GPS-guided farm equipment that could keep the wheels of the tractor or whatever between the planted rows in a field.