Naked Science Forum
Non Life Sciences => Geek Speak => Topic started by: syhprum on 29/10/2011 06:14:49
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Christopher Fry gave a splendid account on TV of how GPS works apparently the "receiving" device transmits to up to four satellites and times the returning pulses to the nearest millisecond and gives the location to within about 30 meters.
This was in reply as to why clocks accurate to one second in thirty billion years are useful.
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of how GPS works apparently the "receiving" device transmits to up to four satellites and times the returning pulses to the nearest millisecond
Er, he's talking cobblers then, cos they don't transmit to anything [:D]
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It is always amusing to listen to actors explain anything technical or to watch them do simple jobs like driving a nail, it is easy to see why they took up acting as there is nowt else they can do.
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I'm not familiar with this
nitwit fellow. You wouldn't happen to have a clip that we can see. I imagine it would be pretty amusing!
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He is a very popular quiz master on a most amusing program QI broadcast both by the BBC and "Dave", I saw it last night (28/10/11).
If you download BBC I you should be able to see a typical episode but not necessarily the one where GPS is described
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It is always amusing to listen to actors explain anything technical or to watch them do simple jobs like driving a nail, it is easy to see why they took up acting as there is nowt else they can do.
I suppose this is a bit off topic, but I was watching a TV show a couple of weeks ago where a family had a "paint party". Everyone had matching, new T-Shirts. There wasn't a drop of paint on any of the actors and actresses. No spots on their spotless clothes.
Clearly they are more coordinated at painting than me!!!
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Just as a note - the only Christopher Fry I have heard of was a playwright who died in 2005 (the lady's not for burning) - I guess you are referring to Stephen Fry.
Its the difference in the time signal received from the satellites. in super simplistic terms if you receive a 123455 from both satellite A and B, a 123454 from C etc you are equidistant from A and B, and twice as far from C. Algorithms allow these differences to be changed into a 3 d position
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Yes, I had heard of Christopher Fry the playwright, but he didn't seem to be in a position to be doing much on the telly. Stephen Fry I am aware of. He's usually hilarious, so I doubt that anyone would take him too seriously.
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It was of course Stephan I had in mind, the old biological memory chips are getting the worse for wear
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I took a look at "GPS" for both camera EXIF data headers on JPEG and TIFF recently , as much as looking at Mapping system coordinates decimal and deg , min , sec and UTM.
Actually , you need to know a little piece of electronics called "SWR" standing wave ratio
standing wave ratio is the height pitch of the elctromagnetic field produced by frequency / speed of light
e.g. if a rise in output strength to reach peak power of oscillation pitch continues for 1/100th of a second the wave is larger in height than one that reaches peak in 1/10000th of a second , its simply how far the field has travelled in a second by density.
Those satellites a are so far away that time lag can be measured (probably in pico seconds at least - milli seconds is quite useles) and as much the sattelites callibrate and check their internal clocks and synchronise them to stay stable.
It's easy to see how if you remember the time lag it took talking to the astronauts, when humans landed on the moon in the nineteen sixties.
You can put sattelites much closer to earth than the moon and have a sensible measurable lag for radio waves.
-Yes the hand set does transmit, because the "request signal" is time lag translated between more than one sattelite(sent to a set of sattelites in different positions so each has the time of signal arrival and there own known position to compare and triangulate in a pyrimid shape down to the point of request signal origin).
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-Yes the hand set does transmit,
Those chappies must be really clever to figure out a way to shrink a whopping great transmitter like that into a little GPS unit. Quite a feat for something that costs less than $100
(They are receive only.)
http://en.wikipedia.org/wiki/Global_Positioning_System#Basic_concept_of_GPS
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Then you are saying there is no sattelite/sattelites used in GPS positioning, the short code pulse has to come from that position physically.
Or are you implying something similar to the time it took an overseas phone call to the other side of the earth that took around 10 - 30 seconds between each point because of lag in receiving the audio, which happens to be security taping it and listening to it then hitting a button between each exchange(of speech) to allow the taping to be played onto the transmitter to be sent.
Then where the hell is the position the person is! , i'll give you a clue, when hunting pigs and foxes(professional vermin extermination : Australia , by law shoot on site) using dogs there are GPS tracking collars, and they have an aerial on the collar.
https://buy.garmin.com/shop/shop.do?pID=89564&ra=true
http://www.barkcontrol.com.au/shop/bark-collars/01?gclid=CJ3mv7bcmawCFaMF4god_CA8Pg
http://www.barkcontrol.com.au/shop/dog-tracking-collars/05
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Sorry! I just edited my post to include this link. GPS receivers only receive.
http://en.wikipedia.org/wiki/Global_Positioning_System#Basic_concept_of_GPS
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Your splitting hairs about the synchronisation of the reciever request signal to the sattelite, in any case it does.
So it calculates the reception of each sattelites time pulse set inverse to transmitting it.
..."implying something similar to the time it took an overseas phone call"...
which is just as sneaky.
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It's not all that sneaky. It's just triangulation (or maybe quadrangulation).
The receiver knows where it is because it knows how far it was from the sats when they were at known locations.
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I assumed that all correspondents were well aware how the GPS system works my post was about the garbled account an actor gave
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Sneakier again!!! thats a bit like saying "because of mathematical prediction of where the sattelites would be" you could then remove them and just press the button from the time of day.
Economically thats viable, the technology is in the handset so the users pay, while all the company needs to pay is for a sattelite that is a second hand spark transmitter, e.g. hauled up from the Titanic.
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This
"Actually , you need to know a little piece of electronics called "SWR" standing wave ratio
standing wave ratio is the height pitch of the elctromagnetic field produced by frequency / speed of light
e.g. if a rise in output strength to reach peak power of oscillation pitch continues for 1/100th of a second the wave is larger in height than one that reaches peak in 1/10000th of a second , its simply how far the field has travelled in a second by density."
is mainly wrong.
The thingy in my car which tells me where I am is receiver and not a transmitter.
Not only is it simply too small to transmit a signal that would reach a satellite with enough power to carry a signal, nor even that if it did so its batteries would last about a minute,
You need to look at the other end.
There are millions of GPS systems. There's no way the satellites could respond to all of them at once.
Read the wiki article and/or think it through.
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it simply too small to transmit a signal that would reach a satellite with enough power to carry a signal, nor even that if it did so its batteries would last about a minute,
Its not a mobile phone or a sattelite phone, so its power sustainability requirements would have been "sweet FA" for both usage in send and sustainability, second, the signals would only need to get above the weather and would need to be around only 10 watts for a fraction of a moment, after the weather , the signal can keep going effectively and be heard on the other side of the universe for human studies.
*Apart from being preposturous, i've thought of something even more silly to think of, with a mobile phone battery system around the size of an ipod and a filtered spark transmitter(no huge adjustment circuits just good generation property for the filters for an intensely short period required), about 50 watts could be generated and would probably always burn through a cyclone.
There are millions of GPS systems. There's no way the satellites could respond to all of them at once.
Certainly no good for a user pay system, until its selling the handsets.
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What does a "User pays" system have to do with the price of fish?
It's designed for the military and they are not normally going to have a few spare coins with them to put into the GPS receiver.
This bit" the signal can keep going effectively and be heard on the other side of the universe for human studies." is nonsense too. The signal would soon get lost among the noise.
While this "Its not a mobile phone or a sattelite phone, so its power sustainability requirements would have been "sweet FA" for both usage in send and sustainability, second, the signals would only need to get above the weather and would need to be around only 10 watts for a fraction of a moment, after the weather "
even if it were true, ignores the fact that my GPS updates its position every few seconds or so.
Nicephotog
READ THIS
http://electronics.howstuffworks.com/gadgets/travel/gps3.htm
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...ignores the fact that my GPS updates its position every few seconds or so.
"every few seconds or so" , mobile phones tx/rx in duplex constantly , why anyone would worry about " 'a few' tiny pips 'a second' " at that type of frequency compared to blazing the side of their head with an oven at point blank.
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...ignores the fact that my GPS updates its position every few seconds or so.
"every few seconds or so" , mobile phones tx/rx in duplex constantly , why anyone would worry about " 'a few' tiny pips 'a second' " at that type of frequency compared to blazing the side of their head with an oven at point blank.
What did you mean by that?
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As an aside, some people may be interested to hear that the MoD are trialing ground based GPS specific jamming systems using a 10 - 15w transmitter which has an expected range in of a few 10's of km...
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I would not want a GPS jammer but I would really like a device to move my apparent location to maybe some nearby military establishment.
Then when the GPS guided missile comes to destroy me it hits something less important.
We did something similar during the war with the guidance system the Luftwaffe were using.
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All you need to do is get enough of the sats to fib about their positions, and that should pretty much take care of it, although it might be possible to fool a receiver with some "synthetic" satellites.
I wonder if that's why certain other countries are creating alternative GPS systems?
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What does a GSP guided missile do if it can't establish its position?
If, as I rather hope, it self destructs, then a jammer would do the job of keeping you safe anyway.
"I wonder if that's why certain other countries are creating alternative GPS systems?"
No, with 2 systems you get better data and less chance of failure.
At the moment the US govt can shut down GPS and it's too useful to let them have that veto.
We want to have our own so we can spend government money on a big project that keeps scientists + engineers off the dole.
Most importantly, it annoys the Americans.
http://en.wikipedia.org/wiki/Galileo_(satellite_navigation)#Tension_with_the_United_States
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Seems like a lot trouble to go to just to annoy Americans.
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Seems like a lot trouble to go to just to annoy Americans.
We like to make the effort and be sure things are done properly
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Seems like a lot trouble to go to just to annoy Americans.
We like to make the effort and be sure things are done properly
One advantage of being an expat is that I can pretend the old country is pretty much the same pleasant place that it was in my youth, i.e., prior to it being taken over by a bunch of raving loonies.
The weather was a lot better then too.
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All you need to do is get enough of the sats to fib about their positions, and that should pretty much take care of it, although it might be possible to fool a receiver with some "synthetic" satellites.
I wonder if that's why certain other countries are creating alternative GPS systems?
Perhaps half of World War III will be fought in space.
Leaving so much orbital debris, that it will set future space programs back a thousand years!!!
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Seems like a lot trouble to go to just to annoy Americans.
We like to make the effort and be sure things are done properly
One advantage of being an expat is that I can pretend the old country is pretty much the same pleasant place that it was in my youth, i.e., prior to it being taken over by a bunch of raving loonies.
The weather was a lot better then too.
You also get to double dip on celebrations - hogmanay and thanksgiving
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It's not unusual for people to ask if there are firework displays on the 4th of July in Britain too.
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It's not unusual for people to ask if there are firework displays on the 4th of July in Britain too.
what we don't tell the americans is that we celebrate the occasion as much, if not more, than they do
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I wonder if that's why certain other countries are creating alternative GPS systems?
Sundials clocks and smoke signals??? amigo!!!
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It's not unusual for people to ask if there are firework displays on the 4th of July in Britain too.
what we don't tell the americans is that we celebrate the occasion as much, if not more, than they do
Oh...
The "Good Riddance of the Pesky Americans" Holiday?
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It's not unusual for people to ask if there are firework displays on the 4th of July in Britain too.
what we don't tell the americans is that we celebrate the occasion as much, if not more, than they do
Oh...
The "Good Riddance of the Pesky Americans" Holiday?
That's the one. It's also what we give thanks for at Thanksgiving.