Yep. Easiest way is to imagine the plane being at one of the vertices of a tetrahedron
Flight 4U 9525
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EddieM
Yep. Easiest way is to imagine the plane being at one of the vertices of a tetrahedron
indeed, but you only need 3 satellite for longitude and latitude (altitude not computable) and of course the "horizontal" separation is much much greater than any "vertical" separation, hence why latitude and longitude are accurate to a few meters whereas altitude is only accurate to ~+- 150m
Knowing the distance from two satellites will locate you somewhere on the rim of a near vertical disc between the satellites. The axle of the disc being the line between the satellites.
Add a third satellite and the there are three discs and only one point where the three rims intersect each other.
If you want to demonstrate it use lengths of string from "satellites" fixed to the floor. Knot the ends and see how the knot can be moved while keeping the strings taut.
Add a third satellite and the there are three discs and only one point where the three rims intersect each other.
If you want to demonstrate it use lengths of string from "satellites" fixed to the floor. Knot the ends and see how the knot can be moved while keeping the strings taut.
According to German Investigators, the co-pilot had been given a sick note and he tore it up on the day, his ex-GF said the 6 years he stopped going for training , he was having nightmares of going down from the skies, and told her that he would make history one day, which we now know for the wrong reason, by his evil actions, he couldn't have gained a name in history by doing something good, as that would be beyond his ability, what a shame, I would pee on his grave for taking lives of innocent people, though given the fact what we are seeing happening in Iraq, he could have achieved a martyrdom by handing himself over to IS in exchange for a release of other captives held there. What a prat he turned out to be.
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GPS uses 24 satellites and so there is a good deal of data that can be computed to arrive at an accurate position as well as altitude, however if data was only received from just a few, then the accuracy may suffer, particularly of altitude.
There is a good read about USA GPS system : http://www.montana.edu/gps/understd.html
There is a good read about USA GPS system : http://www.montana.edu/gps/understd.html
So, you've gone from GPS can't do altitude, to GPS can do altitude (albeit, inaccurately).
Your Garmin quote is for consumer GPS - basically, wandering around the hills on an afternoon-type pursuits. I think this is "relative GPS".
Sure, you could locate aircraft with $79 devices as well.
However, I seem to recall that there is a system called "absolute GPS", where (a specialist) receiver is also triangulated against a base station of known exact coordinates. This can give accuracy to millimetres.
Your Garmin quote is for consumer GPS - basically, wandering around the hills on an afternoon-type pursuits. I think this is "relative GPS".
Sure, you could locate aircraft with $79 devices as well.
However, I seem to recall that there is a system called "absolute GPS", where (a specialist) receiver is also triangulated against a base station of known exact coordinates. This can give accuracy to millimetres.
http://wiki.openstreetmap.org/wiki/Accuracy_of_GPS_data
GPS "knows" exactly where the receiver is (ergo, including "altitude") with just three satellites. "Where the receiver is" being one of two locations.
It discards the one that isn't one or near the Earth's surface, leaving the "exact" position.
GPS "knows" exactly where the receiver is (ergo, including "altitude") with just three satellites. "Where the receiver is" being one of two locations.
It discards the one that isn't one or near the Earth's surface, leaving the "exact" position.
One thing that does spring to mind regarding this is the ground proximity warning system could be rigged to take over control instead of just sounding an alarm.
It could be programmed before the flight to only allow a landing at the destination airport, it would have to be able to be overridden remotely though for emergency landings.
It could be programmed before the flight to only allow a landing at the destination airport, it would have to be able to be overridden remotely though for emergency landings.
gpws only works when near the ground, it takes a feed from radio altimeters which only record below 2500ft.
It is conceivable that the autopilot could be controlled externally by atc for instance, but then if they could control it baddies could too. Also the person in the cockpit would only have to pull a few cb's to disable the autopilot.
It is conceivable that the autopilot could be controlled externally by atc for instance, but then if they could control it baddies could too. Also the person in the cockpit would only have to pull a few cb's to disable the autopilot.
The best solution would be to give each air hostess a pick axe tucked in her fishnet stockings, she could draw it out and chop a head off a would be terrorist and also help- breakdown the pilot's door if need be.
I think I have probably now ruined my chances of ever becoming a pilot!
I think I have probably now ruined my chances of ever becoming a pilot!
I think I have probably now ruined my chances of ever becoming a pilot!
I wouldn't give up hope just yet - you appear to be doing pretty well as a space cadet
Or,
We could all just carry on pretty much as normal.
Otherwise, the nutjobs (and terrorists, when applicable) will have got what they wanted anyway.
We could all just carry on pretty much as normal.
Otherwise, the nutjobs (and terrorists, when applicable) will have got what they wanted anyway.
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EddieM
Not really, I'm just saying I personally can't see how you can work out altitude with any accuracy based on orbital GPS data alone,
I appreciate that they seem to be able to to a not unreasonable degree, but I don't really get it. By my clearly incorrect reckoning altitude would have a very significant margin of error.
I appreciate that they seem to be able to to a not unreasonable degree, but I don't really get it. By my clearly incorrect reckoning altitude would have a very significant margin of error.
Quite superb, if a little harsh on a Mike!
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