How does GPS determine your Altitude?

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Re: How does GPS determine your Altitude?
« Reply #30 on: April 22, 2013, 09:10:21 AM »
The problem when it bends upward is then how do we get GPS signal in the middle of the ocean?
I think, therefore I am

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jason_85

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Re: How does GPS determine your Altitude?
« Reply #31 on: April 22, 2013, 04:01:18 PM »
Quote
You're going to have to clarify how you arrived at those calculations. GPS calculations are carried out via triangulation of coordinates between a large set of satellites, I mean towers; often 5 or more. I also don't see how sensitivity to height would be any less of an issue with satellites, remember that we don't have to assume that all towers are at the same height, so sensitivity to low angles isn't necessary.

Same as above. The further away the transmitters, the longer it takes a signal to get to the receiver,
then, the more accurate the result of the program in the receiver (on a strict time budget)
in timing the distance covered by the signal from each transmitter.
GPS uses triliteration, not triangulation. It looks at the intersection of spheres
of the radius of the calculated distance travelled from each transmitter.
Many of the bonus results can be discarded because they are below sea level where GPS doesn't work.

This is evidence for nothing other than the fact that if the technology used in a RE scenario were at work in a FE scenario, it would not work. It is circular reasoning.

Also, I fail to see how being farther away makes the program more accurate or less computationally intense; if a signal gets sent every x seconds than the receiver will receive and process the data every x seconds. Am I wrong?

I don't really understand this stuff very well, and I'm playing devil's advocate here so please bare with me.
Jason, you are my least favorite noob.

Re: How does GPS determine your Altitude?
« Reply #32 on: April 28, 2013, 03:28:25 AM »
Ok Guys,
I'm bored and up for another round.
Let's say the Earth is Flat, and although GPS works,
there's no machinery in space, so it must be ground based.

The relatively poor GPS hardware in an iPhone can provide an Altitude with estimated accuracy of 5 mtrs without waiting long.

It is my position that in order for GPS to determine your Altitude,
the transmitting antennas must be above the receiver at all times.
So how does the GPS determine Altitude?

Hi Art,

The estimated accuracy of the iPhone you have just stated, I believe to be completely incorrect, if that was the case then you could land aeroplanes with them. As a general rule of thumb the vertical accuracy of a GPS unit is 2-3 times is horizontal accuracy. The horizontal accuracy of an iPhone you probably be lucky to get within 20mtrs, that puts the vertical accuracy out to 40-60mtrs.

Whilst talking about accuracy unless you use real time differential correction, or post processing differential corrections your horizontal accuracy will be poor. For example I use a GeoXH6000 GPS handheld unit almost daily, the pinnacle of hand GPS units (see here for unit specs http://www.trimble.com/mappingGIS/geo6.aspx?dtID=applications& and product comparison http://www.trimble.com/mappingGIS/media/product_comparison/Handheld%20Computers%20With%20GNSS.html before differential correction it has about 2-3 mtr accuracy, after differential correction down to 10cm horizontal accuracy.

Actually the iPhone uses Assisted GPS, and is not a true GPS receiver, as with most cell phones.
You can view the iPhone technical specifications here - https://www.apple.com/au/iphone/specs.html

Assisted GPS or A-GPS devices uses network towers to determine their location and do not need a direct connection to satellites. Easy google search will explain how this works.

Therefore your statement about the transmitting antennas must be above the receiver at times, I would say isn't correct, tho network towers mostly are above you, unless you climb above them (mountain) or are in a aeroplane.

So my question to you is,  If your iPhone or any other A-GPS device gives you a vertical readout of say an approximate accuracy of 40-60 mtrs how do the network towers and the device workout that altitude?




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rottingroom

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Re: How does GPS determine your Altitude?
« Reply #33 on: April 28, 2013, 04:52:57 AM »
GPS provider, of course we all know, but it usually don’t work indoors. It relies on the GPS system with 27 satellites around the earth. At any time, a location needs to be in line-of-sight (LOS) of 4 satellites in order to get latitude, longitude and altitude. To calculate a location, the method is assuming the information from GPS satellite travels at speed of light in vacuum, and both GPS satellite and GPS receiver records the time of transmission and reception of the location data. The distance from GPS satellite to the receiver then can be calculated. 3 satellites are used fro two-dimensional triangulation to get (latitude, longitude), and the fourth satellite calculates the altitude. During this process, if time is out of sync, or GPS signals get reflected or diffracted by high buildings in big cities, errors will occur. To help with these limitations, modern mobile devices use assisted GPS (A-GPS), taking the advantage of mobile network to transmit GPS data.

Using wireless access points. WiFi works better indoors than GPS for sure, and WiFi radio often consumes less battery power than the GPS hardware. WiFi-based location detection works by having a device track what WiFi access points it can detect and the current signal strength of those access points. The device then makes a query to the Google location service (which is different from the Android location service), which provides location data based on the WiFi information. To provide location information based on visible WiFi access points, the Google location service must obtain information about WiFi access points and their locations. This information is collected by Android devices when a user enables use of Google’s location service in the Location Settings. This allows the device to record WiFi information as well as current location information (possibly provided by GPS) and transmit this information to Google. This essentially allows Google use each and every Android device as a way to update the WiFi location information and constantly maintain up-to-date data.

Additionally,  cellular network is used in a similar way as WiFi access points to determine device location. A cellular device must be in contact with a cell tower. As a device moves, it may connect to a different cell tower as the signal strength of an approaching cell tower becomes stronger. Knowing the unique ID of the tower that a device is currently connected to, and possibly the towers that a device was previously connected to, can provide insight to where the device is located assuming the location of a given cell tower is known.

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RealScientist

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Re: How does GPS determine your Altitude?
« Reply #34 on: April 28, 2013, 02:14:49 PM »
Sorry, but you backed the wrong horse. Because of the limitations of the GPS receiver, it is impossible to determine the distance to the transmitter with a precision better than some 2 meters. Divide that by the sine of, say, 0.1 degrees, and you have 2/0.0017 = 1146 meters.

You're going to have to clarify how you arrived at those calculations. GPS calculations are carried out via triangulation of coordinates between a large set of satellites, I mean towers; often 5 or more. I also don't see how sensitivity to height would be any less of an issue with satellites, remember that we don't have to assume that all towers are at the same height, so sensitivity to low angles isn't necessary.
Any amount of towers you have will most probably be far away and will not be a lot higher than your own position. If you had, for example, a tower that is more than 10 degrees above your horizon, you would see it as easily as you see the clouds. Therefore the towers have to be just above your horizon. By contrast, satellites will sometimes be high up in the sky, and with the correct conditions you will see them, just as so many people have.

Towers just cannot be both invisible and higher than the highest buildings in your area. To say you can triangulate using towers that are low enough to not be seen by everybody, and get all three coordinates of your position is to deny that the whole GPS system has some error. Therefore, whatever the GPS system is, we can clearly say what it is not: a system based on towers that are less than a mile high.

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jason_85

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Re: How does GPS determine your Altitude?
« Reply #35 on: April 28, 2013, 04:28:33 PM »
Sorry, but you backed the wrong horse. Because of the limitations of the GPS receiver, it is impossible to determine the distance to the transmitter with a precision better than some 2 meters. Divide that by the sine of, say, 0.1 degrees, and you have 2/0.0017 = 1146 meters.

You're going to have to clarify how you arrived at those calculations. GPS calculations are carried out via triangulation of coordinates between a large set of satellites, I mean towers; often 5 or more. I also don't see how sensitivity to height would be any less of an issue with satellites, remember that we don't have to assume that all towers are at the same height, so sensitivity to low angles isn't necessary.
Any amount of towers you have will most probably be far away and will not be a lot higher than your own position. If you had, for example, a tower that is more than 10 degrees above your horizon, you would see it as easily as you see the clouds. Therefore the towers have to be just above your horizon. By contrast, satellites will sometimes be high up in the sky, and with the correct conditions you will see them, just as so many people have.

Towers just cannot be both invisible and higher than the highest buildings in your area. To say you can triangulate using towers that are low enough to not be seen by everybody, and get all three coordinates of your position is to deny that the whole GPS system has some error. Therefore, whatever the GPS system is, we can clearly say what it is not: a system based on towers that are less than a mile high.

If there is a global conspiracy then it wouldn't be much of a stretch to assume that they are using existing mobile tower infrastructure, so you could have relatively significant angles of inclination because those towers are so densely distributed.
Jason, you are my least favorite noob.

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RealScientist

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Re: How does GPS determine your Altitude?
« Reply #36 on: May 03, 2013, 10:47:14 AM »
Sorry, but you backed the wrong horse. Because of the limitations of the GPS receiver, it is impossible to determine the distance to the transmitter with a precision better than some 2 meters. Divide that by the sine of, say, 0.1 degrees, and you have 2/0.0017 = 1146 meters.

You're going to have to clarify how you arrived at those calculations. GPS calculations are carried out via triangulation of coordinates between a large set of satellites, I mean towers; often 5 or more. I also don't see how sensitivity to height would be any less of an issue with satellites, remember that we don't have to assume that all towers are at the same height, so sensitivity to low angles isn't necessary.
Any amount of towers you have will most probably be far away and will not be a lot higher than your own position. If you had, for example, a tower that is more than 10 degrees above your horizon, you would see it as easily as you see the clouds. Therefore the towers have to be just above your horizon. By contrast, satellites will sometimes be high up in the sky, and with the correct conditions you will see them, just as so many people have.

Towers just cannot be both invisible and higher than the highest buildings in your area. To say you can triangulate using towers that are low enough to not be seen by everybody, and get all three coordinates of your position is to deny that the whole GPS system has some error. Therefore, whatever the GPS system is, we can clearly say what it is not: a system based on towers that are less than a mile high.

If there is a global conspiracy then it wouldn't be much of a stretch to assume that they are using existing mobile tower infrastructure, so you could have relatively significant angles of inclination because those towers are so densely distributed.
So densely distributed in the most densely populated cities. In open plains there are not nearly enough. But even in the densest cities you rarely see an antenna that is at an apparent altitude of more than 10 degrees or so from your location. You could get a very imprecise and inconsistent altitude reading, even in New York. Remember, people get accurate readings everywhere in the world, except from the inside of large buildings. Even if you find a few places on Earth where the Celular antennas could double up as GPS transmitters, the vast majority of the world would have a totally unreliable GPS altitude reading.

In fact, I am close to the densest array of Celular antennas in my whole country, and the apparent altitude of the highest antenna I can find is less than 5 degrees. Not enough to fool my GPS.

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jason_85

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Re: How does GPS determine your Altitude?
« Reply #37 on: May 05, 2013, 06:13:06 AM »
Sorry, but you backed the wrong horse. Because of the limitations of the GPS receiver, it is impossible to determine the distance to the transmitter with a precision better than some 2 meters. Divide that by the sine of, say, 0.1 degrees, and you have 2/0.0017 = 1146 meters.

You're going to have to clarify how you arrived at those calculations. GPS calculations are carried out via triangulation of coordinates between a large set of satellites, I mean towers; often 5 or more. I also don't see how sensitivity to height would be any less of an issue with satellites, remember that we don't have to assume that all towers are at the same height, so sensitivity to low angles isn't necessary.
Any amount of towers you have will most probably be far away and will not be a lot higher than your own position. If you had, for example, a tower that is more than 10 degrees above your horizon, you would see it as easily as you see the clouds. Therefore the towers have to be just above your horizon. By contrast, satellites will sometimes be high up in the sky, and with the correct conditions you will see them, just as so many people have.

Towers just cannot be both invisible and higher than the highest buildings in your area. To say you can triangulate using towers that are low enough to not be seen by everybody, and get all three coordinates of your position is to deny that the whole GPS system has some error. Therefore, whatever the GPS system is, we can clearly say what it is not: a system based on towers that are less than a mile high.

If there is a global conspiracy then it wouldn't be much of a stretch to assume that they are using existing mobile tower infrastructure, so you could have relatively significant angles of inclination because those towers are so densely distributed.
So densely distributed in the most densely populated cities. In open plains there are not nearly enough. But even in the densest cities you rarely see an antenna that is at an apparent altitude of more than 10 degrees or so from your location. You could get a very imprecise and inconsistent altitude reading, even in New York. Remember, people get accurate readings everywhere in the world, except from the inside of large buildings. Even if you find a few places on Earth where the Celular antennas could double up as GPS transmitters, the vast majority of the world would have a totally unreliable GPS altitude reading.

In fact, I am close to the densest array of Celular antennas in my whole country, and the apparent altitude of the highest antenna I can find is less than 5 degrees. Not enough to fool my GPS.

While I agree with you, I do not think this is a valid argument against the FET model. Supposing hypothetically that the towers were used to obtain location readings for GPS, it stands to reason that whoever designed them would have done so with the intention of fooling the masses about how they work. Since everyone is lead to believe that they operate by receiving pines from satellites, it would seem logical that the designers would rig them in such a way that they would function as if they were obtaining their signal from said satellites. The designers would have to lie about their accuracy and deliberately reduce latitude and longitude reading accuracy to give the perception that the reading was from satellites.
Jason, you are my least favorite noob.

Re: How does GPS determine your Altitude?
« Reply #38 on: May 05, 2013, 08:17:16 AM »
Why does my handheld GPS work anywhere where I have line of sight.
Also why doesnt it work when I do not?
Also why does my phone work no matter if I have line of sight or not, but fails when I away from a tower?

Seems to me satellites are an answer to all these questions.
If the sun/moon can circle the earth, why cant a satellite?

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RealScientist

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Re: How does GPS determine your Altitude?
« Reply #39 on: May 05, 2013, 10:01:30 AM »
While I agree with you, I do not think this is a valid argument against the FET model. Supposing hypothetically that the towers were used to obtain location readings for GPS, it stands to reason that whoever designed them would have done so with the intention of fooling the masses about how they work. Since everyone is lead to believe that they operate by receiving pines from satellites, it would seem logical that the designers would rig them in such a way that they would function as if they were obtaining their signal from said satellites. The designers would have to lie about their accuracy and deliberately reduce latitude and longitude reading accuracy to give the perception that the reading was from satellites.
My whole point is that lying is not enough. you have to make an astounding technological breakthrough to make the system accurate to about 5 cm, and then lie about it saying that it can only work to so some 5 meters of accuracy. You have to lie to the manufacturers of the chips inside the GPS so they get them to work with measurements of time accurate to about a nanosecond, when they are tough at work trying to get the measurements accurate to less than a tenth of a microsecond.

It is like telling you that you have to make a computer with a 40 GHz clock even though the best you have ever seen is 4 GHz, and do it for no reason you can speak of. And you know that people have been trying to break the 4 GHz barrier for years, with out much luck.

If I could improve the accuracy of electronic time measuring by two orders of magnitude and also blow a world wide conspiracy, and become a billionaire in the process, I would do so and the hell with the global conspiracy.

Re: How does GPS determine your Altitude?
« Reply #40 on: May 05, 2013, 05:29:43 PM »
since the FAQ has been edited to point it is useless and the wiki does not address this, as Zetetics, we must conclude man mad objects do rotate the disc.

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Son of Orospu

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Re: How does GPS determine your Altitude?
« Reply #41 on: May 06, 2013, 07:03:52 AM »
since the FAQ has been edited to point it is useless and the wiki does not address this, as Zetetics, we must conclude man mad objects do rotate the disc.

Since you are always bashing the FAQ, you are more than welcome to write a new one and submit it for approval. 

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jason_85

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Re: How does GPS determine your Altitude?
« Reply #42 on: May 06, 2013, 04:42:18 PM »
While I agree with you, I do not think this is a valid argument against the FET model. Supposing hypothetically that the towers were used to obtain location readings for GPS, it stands to reason that whoever designed them would have done so with the intention of fooling the masses about how they work. Since everyone is lead to believe that they operate by receiving pines from satellites, it would seem logical that the designers would rig them in such a way that they would function as if they were obtaining their signal from said satellites. The designers would have to lie about their accuracy and deliberately reduce latitude and longitude reading accuracy to give the perception that the reading was from satellites.
My whole point is that lying is not enough. you have to make an astounding technological breakthrough to make the system accurate to about 5 cm, and then lie about it saying that it can only work to so some 5 meters of accuracy. You have to lie to the manufacturers of the chips inside the GPS so they get them to work with measurements of time accurate to about a nanosecond, when they are tough at work trying to get the measurements accurate to less than a tenth of a microsecond.

It is like telling you that you have to make a computer with a 40 GHz clock even though the best you have ever seen is 4 GHz, and do it for no reason you can speak of. And you know that people have been trying to break the 4 GHz barrier for years, with out much luck.

If I could improve the accuracy of electronic time measuring by two orders of magnitude and also blow a world wide conspiracy, and become a billionaire in the process, I would do so and the hell with the global conspiracy.

Well it depends on how you define the scope of the supposed conspiracy. Since everyone who believes FET is an idiot, I see no reason why I shouldn't be allowed to scope the conspiracy however I choose when playing devil's advocate. So here it is:

Our own understanding of the computational capacity of floating point operations on a microchip is wrong. Handheld devices are actually capable of processing trilateration operations at a higher capacity than we are lead to be believe, and the true capacity of portable GPS is that which gives the altitude readings from a series of GPS towers. The latitude/longitude readings are simply throttled in order to give the perception of a satellite system.
Jason, you are my least favorite noob.

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jason_85

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Re: How does GPS determine your Altitude?
« Reply #43 on: May 06, 2013, 04:43:13 PM »
If I could improve the accuracy of electronic time measuring by two orders of magnitude and also blow a world wide conspiracy, and become a billionaire in the process, I would do so and the hell with the global conspiracy.

You would be assassinated by NASA goons.
Jason, you are my least favorite noob.

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RealScientist

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Re: How does GPS determine your Altitude?
« Reply #44 on: May 09, 2013, 04:51:19 AM »
While I agree with you, I do not think this is a valid argument against the FET model. Supposing hypothetically that the towers were used to obtain location readings for GPS, it stands to reason that whoever designed them would have done so with the intention of fooling the masses about how they work. Since everyone is lead to believe that they operate by receiving pines from satellites, it would seem logical that the designers would rig them in such a way that they would function as if they were obtaining their signal from said satellites. The designers would have to lie about their accuracy and deliberately reduce latitude and longitude reading accuracy to give the perception that the reading was from satellites.
My whole point is that lying is not enough. you have to make an astounding technological breakthrough to make the system accurate to about 5 cm, and then lie about it saying that it can only work to so some 5 meters of accuracy. You have to lie to the manufacturers of the chips inside the GPS so they get them to work with measurements of time accurate to about a nanosecond, when they are tough at work trying to get the measurements accurate to less than a tenth of a microsecond.

It is like telling you that you have to make a computer with a 40 GHz clock even though the best you have ever seen is 4 GHz, and do it for no reason you can speak of. And you know that people have been trying to break the 4 GHz barrier for years, with out much luck.

If I could improve the accuracy of electronic time measuring by two orders of magnitude and also blow a world wide conspiracy, and become a billionaire in the process, I would do so and the hell with the global conspiracy.

Well it depends on how you define the scope of the supposed conspiracy. Since everyone who believes FET is an idiot, I see no reason why I shouldn't be allowed to scope the conspiracy however I choose when playing devil's advocate. So here it is:

Our own understanding of the computational capacity of floating point operations on a microchip is wrong. Handheld devices are actually capable of processing trilateration operations at a higher capacity than we are lead to be believe, and the true capacity of portable GPS is that which gives the altitude readings from a series of GPS towers. The latitude/longitude readings are simply throttled in order to give the perception of a satellite system.
Good idea, but that movie has already been done. It is called "Matrix", and I believe none of the authors and producers has been killed by NASA goons.

Your half baked (or should we say, still completely raw) version of the movie is, by far, too little too late.

Re: How does GPS determine your Altitude?
« Reply #45 on: May 11, 2013, 07:01:41 AM »
Ok Guys,
I'm bored and up for another round.
Let's say the Earth is Flat, and although GPS works,
there's no machinery in space, so it must be ground based.

The relatively poor GPS hardware in an iPhone can provide an Altitude with estimated accuracy of 5 mtrs without waiting long.

It is my position that in order for GPS to determine your Altitude,
the transmitting antennas must be above the receiver at all times.
So how does the GPS determine Altitude?

The earth is not COMPLETELY flat.  There are hills and vallies.  The GPS equipment is located at different altitudes and will be different distances from your phone.  The fact that it actually stays still makes the calculations much easier than the idea of having "satellites" in "geo-stable" "orbit".