Magnetic north point moving fast

Interesting, I always thought it was global, hence the name. But I'm also not surprised that coverage may lack or be non existent in wide open parts of the south pacific ocean. Is this that map accurate for all GPS? On the Volvo Ocean Races I was pretty the teams had GPS coverage even in those dark areas.. but maybe not?

That's what I thought.. but given that it is generated by geosynchronous satellites I wouldn't be surprised if it is not in all areas available.. does it make sense to operate and maintain a satellite that you don't really need?

GPS satellites are not geosynchronous - If they were, you would always be receiving the same ones when you're in the same spot.

As such, coverage IS global - I don't know where that map that @Dan Thomas posted came from.
 
GPS satellites are not geosynchronous
Interesting, I thought I read somewhere that they were, and the map from Dan with the blank areas seemed to support that. But I stand corrected.. which raises the question, why would a "global" positioning system have blanks on it??

*as a further tantalizing thought exercise, could spacecraft going to the moon theoretically map their location using the GPS satellites?

*EDIT: I remember, INMARSAT has geostationary satellites, I learned that when I was closely following the MH370 saga..

upload_2019-1-11_17-6-43.png
 
Nope. GPS coverage is not completely global. The various maps I find differ a bit, but the coverages look similar to this:

7816824-12121968.jpg


Some of the mid-latitude ocean should be OK but WAAS would be inop. It's the poles that don't appear to be covered well.
I do question that map as I've had no problems with GPS in the part of India showing an area of "poor coverage" I'm also pretty sure Hawaii is in one of the depicted "poor coverage" zones as well, and I've had no issues there. Likewise, Cape Horn, the southern tip of South America gave me no trouble with GPS.
 
Interesting, I thought I read somewhere that they were, and the map from Dan with the blank areas seemed to support that. But I stand corrected.. which raises the question, why would a "global" positioning system have blanks on it??

*as a further tantalizing thought exercise, could spacecraft going to the moon theoretically map their location using the GPS satellites?

*EDIT: I remember, INMARSAT has geostationary satellites, I learned that when I was closely following the MH370 saga..

View attachment 70685
Probably, for at least a while. I don't know how for out a spacecraft would go before there insufficient variation in reception times to calculate a good position. When there were fewer GPS satellites, sometimes the visible satellites would be in a geometry where there wasn't enough difference in timing to calculate a good solution.

GPS works by measuring the time a signal is received, compared to the time it was sent. Knowing the speed of light, one can calculate a sphere of distance around each satellite. The spheres intersect at your location. Far enough away, the satellites appear to be close to one another in the sky, so there aren't really intersecting spheres, anymore. There is also a correction for relativity, and this would need to be adjusted for something moving away from the mass of the earth (http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html ).
 
Probably, for at least a while ... GPS works by measuring the time a signal is received, compared to the time it was sent. Knowing the speed of light, one can calculate a sphere of distance around each satellite. The spheres intersect at your location. Far enough away, the satellites appear to be close to one another in the sky, so there aren't really intersecting spheres, anymore. There is also a correction for relativity, and this would need to be adjusted for something moving away from the mass of the earth (http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html ).

All true. The real problem, though, is that the transmitting antennas on the satellites are highly directional. I had to hunt for it (Google wants to show GPS receiving antennas), but from looking at the pattern on the Block IIF series, for example, the beam width is less than 20 degrees, focused on Earth. There would be very little signal radiated to the sides, and virtually none to the rear. Some low earth orbit satellites have used GPS, but I can't see it being used on a mission very far from Earth.

This thread has already drifted away from the original Geomagnetic issue, but incidentally, I was astonished at how large those GPS satellites are -- thousands of pounds, with big honkin' flywheels for fine positioning!o_O
 
The poles flip about every million years, if I recall my university geology correctly. We are overdue for a change. There are concerns that the magnetic field may collapse for a while during the transition exposing us to hazardous 'cosmic rays'.

As I understand it no one really knows how the field arises or what causes the flips.

Pole reversal is the "conclusive" evidence for seafloor spreading which is a key mechanism in the movement of the continental plates. I can roughly recall the Atlantic case.

The US and Europe are slowly getting further apart. There is a volcanic ridge runs down the middle of the Atlantic. As continents move apart the molten rock comes out the slot and solidifies filling the gap. It takes on the local magnetic field as it does so.

midridge.gif


There are consequent bands of opposing polarity baked into the rocks across the Atlantic ocean. This was found round about the '60s when Magnetic Anomaly Detectors became available. The MADs may have been developed for detecting submerged submarines and/or for oil exploration.

seaflor2.gif


Lockheed Orion with MAD boom.

P-3_prototype_NAN1-59.jpg


Theory of Plate Tectonics.
Continental Drift.
Gondwanaland.


Most of the above is likely mostly OK. :)

There is no connection to the accumulation of the greenhouse gas CO2 in the atmosphere.

http://www.phy6.org/earthmag/reversal.htm
I shall validate your Earth science, for I am a geologist. You are correct. To really nerd out:. The sea floor rock, being ultra mafic, (high in Fe+) has crystals of Magnatite that align with the poles while they grow during the cooling process at the divergent zones in the rifts.
 
Haha. We didn't have any trouble with GPS in that section of West Africa that's supposedly not covered!
 
The turtles are waking up - stuff 'bout to get real...
 
The turtles are waking up - stuff 'bout to get real...

https://en.wikipedia.org/wiki/Turtles_all_the_way_down

The following anecdote is told of William James. [...] After a lecture on cosmology and the structure of the solar system, James was accosted by a little old lady.

"Your theory that the sun is the centre of the solar system, and the earth is a ball which rotates around it has a very convincing ring to it, Mr. James, but it's wrong. I've got a better theory," said the little old lady.

"And what is that, madam?" inquired James politely.

"That we live on a crust of earth which is on the back of a giant turtle."

Not wishing to demolish this absurd little theory by bringing to bear the masses of scientific evidence he had at his command, James decided to gently dissuade his opponent by making her see some of the inadequacies of her position.

"If your theory is correct, madam," he asked, "what does this turtle stand on?"

"You're a very clever man, Mr. James, and that's a very good question," replied the little old lady, "but I have an answer to it. And it's this: The first turtle stands on the back of a second, far larger, turtle, who stands directly under him."

"But what does this second turtle stand on?" persisted James patiently.

To this, the little old lady crowed triumphantly,

"It's no use, Mr. James — it's turtles all the way down."
 
https://en.wikipedia.org/wiki/Turtles_all_the_way_down

The following anecdote is told of William James. [...] After a lecture on cosmology and the structure of the solar system, James was accosted by a little old lady.

"Your theory that the sun is the centre of the solar system, and the earth is a ball which rotates around it has a very convincing ring to it, Mr. James, but it's wrong. I've got a better theory," said the little old lady.

"And what is that, madam?" inquired James politely.

"That we live on a crust of earth which is on the back of a giant turtle."

Not wishing to demolish this absurd little theory by bringing to bear the masses of scientific evidence he had at his command, James decided to gently dissuade his opponent by making her see some of the inadequacies of her position.

"If your theory is correct, madam," he asked, "what does this turtle stand on?"

"You're a very clever man, Mr. James, and that's a very good question," replied the little old lady, "but I have an answer to it. And it's this: The first turtle stands on the back of a second, far larger, turtle, who stands directly under him."

"But what does this second turtle stand on?" persisted James patiently.

To this, the little old lady crowed triumphantly,

"It's no use, Mr. James — it's turtles all the way down."
But it is a flat turtle
 
Nope. GPS coverage is not completely global. The various maps I find differ a bit, but the coverages look similar to this:

7816824-12121968.jpg


Some of the mid-latitude ocean should be OK but WAAS would be inop. It's the poles that don't appear to be covered well.

As mentioned in another thread, GPS in northern Norway is being jammed by Russia. Also, criminals with cheap GPS jammers plugged into auto cogarette lighters have caused ambulance helicopters to lose GPS totally for some minutes.

The jamming devices use are on the rise. Kind of alarming I’d the backups like compass start being unreliable.
 
I foresee a market for giant LCD screens with real-time updates embedded in the approach ends of runways.....

Here in Atlanta we have digital speed limit signs on I285 (not sure about 75 and 85), and they change depending on the traffic. Don't really need an LED screen per se.

9KDSlOh.jpg
 
Here in Atlanta we have digital speed limit signs on I285 (not sure about 75 and 85), and they change depending on the traffic. Don't really need an LED screen per se.

9KDSlOh.jpg
Only on 285 and they're just a suggestion ;)
 
The poles flip about every million years, if I recall my university geology correctly. We are overdue for a change. There are concerns that the magnetic field may collapse for a while during the transition exposing us to hazardous 'cosmic rays'.

As I understand it no one really knows how the field arises or what causes the flips.

Pole reversal is the "conclusive" evidence for seafloor spreading which is a key mechanism in the movement of the continental plates. I can roughly recall the Atlantic case.

The US and Europe are slowly getting further apart. There is a volcanic ridge runs down the middle of the Atlantic. As continents move apart the molten rock comes out the slot and solidifies filling the gap. It takes on the local magnetic field as it does so.

midridge.gif


There are consequent bands of opposing polarity baked into the rocks across the Atlantic ocean. This was found round about the '60s when Magnetic Anomaly Detectors became available. The MADs may have been developed for detecting submerged submarines and/or for oil exploration.

seaflor2.gif


Lockheed Orion with MAD boom.

P-3_prototype_NAN1-59.jpg


Theory of Plate Tectonics.
Continental Drift.
Gondwanaland.


Most of the above is likely mostly OK. :)

There is no connection to the accumulation of the greenhouse gas CO2 in the atmosphere.

http://www.phy6.org/earthmag/reversal.htm

Hope someone has alerted the Congress about this. Surely they can fix it with legislation. Always suspected one of our fearless leaders would pass a law requiring the sun to rise in the west, just to be equal


Sent from my iPad using Tapatalk
 
GPS works just fine at the South Pole station in Antarctica.
It can be used not just for position, but for keeping very precise time.
Plenty o' satellites, not geosynchronous.

Edit: there's an approach plate for the South Pole station, and it's a GPS approach.
 
My cousin worked on the radio and navigational systems on the B52 until recently and he said it was just a few years ago they got rid of the sextant on board! Maybe they better go grab em back!

For me once off flying on my own again, took a few year hiatus and am now getting my TW endorsement for my "new" plane, I plan on doing much of my traveling with paper maps and reading water towers- just because its fun and keeps you more engaged than flying the magenta line. I'm not saying I wont ever bring foreflight with me, but there is a time to read water towers and fly train tracks too. I find real enjoyment in doing things without all the tech aids... Well I guess thats why I purposefully bought a 40's era rig with no modern navigational updates. Though I'm hoping the compass keeps working-that would still be nice to use :)
 
Watch out for solar flares... mucks up the whole system....
 
We need to invest huge sums of money into green tech because____________
 
I looked at the chart at the beginning of that article and it appeared to show the opposite of the fear mongering headline. Since 2010 it’s slowed a bit.

That. It's nearer true north than it has been for years. The horror of it all.
 
Geostationary is when it doesn't appear to move at all, but I think most geosynchronous orbits would remain "visible" at all times as well.

GPS satellites are halfway out, in a semi-synchronous orbit.

Probably worth noting: The WAAS satellites are actually geostationary, but they're a bit special and not part of the GPS constellation. WAAS coverage is limited to a much smaller area, however.

800px-WAAS_service_area.png
 
My cousin worked on the radio and navigational systems on the B52 until recently and he said it was just a few years ago they got rid of the sextant on board! Maybe they better go grab em back!

For me once off flying on my own again, took a few year hiatus and am now getting my TW endorsement for my "new" plane, I plan on doing much of my traveling with paper maps and reading water towers- just because its fun and keeps you more engaged than flying the magenta line. I'm not saying I wont ever bring foreflight with me, but there is a time to read water towers and fly train tracks too. I find real enjoyment in doing things without all the tech aids... Well I guess thats why I purposefully bought a 40's era rig with no modern navigational updates. Though I'm hoping the compass keeps working-that would still be nice to use :)

IFR = I follow roads


Sent from my iPad using Tapatalk
 
What’s the deal with all of the turtle references?
 
I think we would keep latitude N/S as is, and just renumber compasses. Is it legal to have a 180° correction?


Tom


But that would mean ANDS would no longer work, and we'd have to invent a new acronym. Imagine the time and expense necessary, the books that would have to be re-written, the pilot exams that would need updates,....
 
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