Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #40 on: February 10, 2020, 01:02:25 PM »
You found an answer - unfortunately it is a wrong one.
GPS is independent of cell towers. GPS has been in place and working long before cell towers were able to provide adequate positioning services for end users.
I am wondering why you would deliberately post false information?

Cell phone location detection was introduced in 1996.

GPS wasn't commercially available until 1999.
« Last Edit: February 11, 2020, 01:00:12 PM by totallackey »

Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #41 on: February 10, 2020, 01:08:09 PM »
My commutes take place on county roads, city streets, state and US highways and Interstates.

My commutes requiring the use of Google Maps and Garmin and TomTom involve an automobile.

What personal evidence do you have that GPS works in the middle of oceans?

These days it's sometimes difficult to differentiate between different "methods", in this case "GPS" and "mobile data".
Modern devices, esp. smartphones, will draw on any available data for positioning.
As you don't go into any detail of your setup, this doesn't prove/disprove anything.

Why would your commute require "Google Maps and Garmin and TomTom", if that's what you meant?
Either one should - if used correctly - be sufficient.

My personal experience with several devices (some of them pure GPS devices) is, that they work globally - even with no data service.

iC
Let me clarify.

I have used each of the services and devices at varying times.

I have had a cell phone (of one type or another) since 1999.

What I have found is the GPS and the cell phone lost signal at roughly the same time.

While correlation =/= causation, I find it highly suspect and tend to side with the idea it is indeed more likely that GPS tracking and cellular service is occurring at roughly the same altitude (i.e., the height of the average cell phone tower).

Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #42 on: February 10, 2020, 04:58:35 PM »
My commutes take place on county roads, city streets, state and US highways and Interstates.

My commutes requiring the use of Google Maps and Garmin and TomTom involve an automobile.

What personal evidence do you have that GPS works in the middle of oceans?

These days it's sometimes difficult to differentiate between different "methods", in this case "GPS" and "mobile data".
Modern devices, esp. smartphones, will draw on any available data for positioning.
As you don't go into any detail of your setup, this doesn't prove/disprove anything.

Why would your commute require "Google Maps and Garmin and TomTom", if that's what you meant?
Either one should - if used correctly - be sufficient.

My personal experience with several devices (some of them pure GPS devices) is, that they work globally - even with no data service.

iC
Let me clarify.

I have used each of the services and devices at varying times.

I have had a cell phone (of one type or another) since 1999.

What I have found is the GPS and the cell phone lost signal at roughly the same time.

While correlation =/= causation, I find it highly suspect and tend to side with the idea it is indeed more likely that GPS tracking and cellular service is occurring at roughly the same altitude (i.e., the height of the average cell phone tower).
How do you explain that a GPNSS receiver typically shows reception from up to 20 transmitters from US, Russia, Europe and China?

Your theory means that when the US sends a missile to another country it relies on their mobile phone network working.
« Last Edit: February 10, 2020, 05:49:28 PM by inquisitive »

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Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #43 on: February 10, 2020, 07:40:45 PM »
GPS is independent of cell towers. GPS has been in place and working long before cell towers were able to provide adequate positioning services for end users.
I am wondering why you would deliberately post false information?
Cell phone location detection was introduced in 1996.
GPS was commercially available until 1999.

I do apologize for creating the impression of "deliberately posting false information".
However, I fail to see any false information in my post.

Cell phone location detection in the late 1990s was network based and its infancy as suggested by your own choice of words: "introduced". It was at the time relatively inaccurate and aimed at service providers - not at end users.
AFAIK cell towers still do not provide actual positioning services for end users; i.e. as an end user does not get the raw data that would be needed to determine the mobile phone's geographical location accurately (as is the case with GPS).
Furthermore the density of cell towers (esp. in rural areas or on large bodies of water) was much lower in the 90s, resulting in non-adequate coverage (again in contrast to GPS).
=> GPS (using dedicated GPS devices) was working accurately when cell tower based positioning wasn't.

GPS Initial Operational Capability (IOC) was declared in 1993 (https://web.archive.org/web/20110126200746/http://tycho.usno.navy.mil/gpsinfo.html), i.e. it was "in place and working".
I did not claim that it was commercially available, although it was even before 1993: https://mashable.com/2014/05/25/commercial-gps-25-anniversary/
 "As a result of the government's GPS openness, this weekend we commemorate the 25th anniversary of the first consumer handheld GPS device. On May 25, 1989, the first Magellan GPS NAV 1000s were shipped to retailers."
=> GPS has been in place and working long before cell towers were able to provide adequate positioning services for end users.

Please let me know, if I've overlooked something, but it looks like my information is correct, whereas your date for commercial availability is at least 10 years late, while the date you give for cell phone location detection is significantly early.


iC

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Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #44 on: February 10, 2020, 08:11:28 PM »
Let me clarify.

I have used each of the services and devices at varying times.

I have had a cell phone (of one type or another) since 1999.

What I have found is the GPS and the cell phone lost signal at roughly the same time.

While correlation =/= causation, I find it highly suspect and tend to side with the idea it is indeed more likely that GPS tracking and cellular service is occurring at roughly the same altitude (i.e., the height of the average cell phone tower).

I'm sorry for not being more explicit in my previous post.
"As you don't go into any detail of your setup, this doesn't prove/disprove anything." was meant to encourage you to provide more detail.

To get from correlation to causation one would e.g. need to know:
  • Can the effect be reproduced reliably (same/other locations/tines)?
  • Can the effect be reproduced with different phones/GPS?
  • Do both devices always loose signals at the same time? Or does is it sometimes only one or the other?
  • Is the signal really lost or just "useless"? (e.g. GPS not getting enough satellites to triangulate or mobile phone getting wrong provider)
  • Where does and where doesn't it happen? => What might be possible reasons?
  • Why would that suggest the same altitude? (Average height of a cell phone tower isn't really a useful concept => on building, on hills, on mountains, ...)

I have had a cell phone (of one type or another) since at least 1994 - so what does that fact add to the discussion?

iC

Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #45 on: February 11, 2020, 12:53:42 PM »
Let me clarify.

I have used each of the services and devices at varying times.

I have had a cell phone (of one type or another) since 1999.

What I have found is the GPS and the cell phone lost signal at roughly the same time.

While correlation =/= causation, I find it highly suspect and tend to side with the idea it is indeed more likely that GPS tracking and cellular service is occurring at roughly the same altitude (i.e., the height of the average cell phone tower).

I'm sorry for not being more explicit in my previous post.
"As you don't go into any detail of your setup, this doesn't prove/disprove anything." was meant to encourage you to provide more detail.

To get from correlation to causation one would e.g. need to know:
  • Can the effect be reproduced reliably (same/other locations/tines)?
  • Can the effect be reproduced with different phones/GPS?
  • Do both devices always loose signals at the same time? Or does is it sometimes only one or the other?
  • Is the signal really lost or just "useless"? (e.g. GPS not getting enough satellites to triangulate or mobile phone getting wrong provider)
  • Where does and where doesn't it happen? => What might be possible reasons?
  • Why would that suggest the same altitude? (Average height of a cell phone tower isn't really a useful concept => on building, on hills, on mountains, ...)

I have had a cell phone (of one type or another) since at least 1994 - so what does that fact add to the discussion?

iC
It means you are saying 36,000 km far from earth satellite are suitable for telling out location but 1 km far from my location installed tower aren't? I have studied Architect Engineering and I know how to draw map for buildings and roads. Everything in map is benchmark to each other like one signal tower to other and so on. Now if you ask me I can draw map and create my own GPS for my city. I will draw map of my city and specify 1km=cm/inch (unit set). now I will mark each signal tower as benchmark and whoever getting signal from will be traced like how far he is from signal tower and in which direction.

In 2002/2003 I shocked when I saw my town location right under time on my mobile (Samsung c220) in Pakistan. And this location was definitely took from signal towers. Also if smartphones are taking location from satellite then how my Old desktop showing my location on my Google Chrome Browser? Definitely from my router. right? but my router is connected through optical fibre with my internet providers server my question is how they are tracing my location?

Only Answer came in my mind is: My IP location which benchmarks my routers location on map? Correct me if I am not wrong.

Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #46 on: February 11, 2020, 01:01:05 PM »
GPS is independent of cell towers. GPS has been in place and working long before cell towers were able to provide adequate positioning services for end users.
I am wondering why you would deliberately post false information?
Cell phone location detection was introduced in 1996.
GPS was commercially available until 1999.

I do apologize for creating the impression of "deliberately posting false information".
However, I fail to see any false information in my post.

Cell phone location detection in the late 1990s was network based and its infancy as suggested by your own choice of words: "introduced". It was at the time relatively inaccurate and aimed at service providers - not at end users.
AFAIK cell towers still do not provide actual positioning services for end users; i.e. as an end user does not get the raw data that would be needed to determine the mobile phone's geographical location accurately (as is the case with GPS).
Furthermore the density of cell towers (esp. in rural areas or on large bodies of water) was much lower in the 90s, resulting in non-adequate coverage (again in contrast to GPS).
=> GPS (using dedicated GPS devices) was working accurately when cell tower based positioning wasn't.

GPS Initial Operational Capability (IOC) was declared in 1993 (https://web.archive.org/web/20110126200746/http://tycho.usno.navy.mil/gpsinfo.html), i.e. it was "in place and working".
I did not claim that it was commercially available, although it was even before 1993: https://mashable.com/2014/05/25/commercial-gps-25-anniversary/
 "As a result of the government's GPS openness, this weekend we commemorate the 25th anniversary of the first consumer handheld GPS device. On May 25, 1989, the first Magellan GPS NAV 1000s were shipped to retailers."
=> GPS has been in place and working long before cell towers were able to provide adequate positioning services for end users.

Please let me know, if I've overlooked something, but it looks like my information is correct, whereas your date for commercial availability is at least 10 years late, while the date you give for cell phone location detection is significantly early.


iC
It looks like your information is false still.

Again, GPS wasn't commercially available until 1999.

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Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #47 on: February 11, 2020, 01:49:20 PM »
.... how my Old desktop showing my location on my Google Chrome Browser? Definitely from my router. right? but my router is connected through optical fibre with my internet providers server my question is how they are tracing my location?

Only Answer came in my mind is: My IP location which benchmarks my routers location on map? Correct me if I am not wrong.

https://stackoverflow.com/questions/1668304/how-does-google-calculate-my-location-on-a-desktop

If you connect to your Internet Service Provider via a landline, then your ISP knows where your landline is, where their local routers are, and where the Point Of Presence connecting to an internet "branch" is. 

This is totally different from how your mobile phone gets its location
Not Flat. Happy to prove this, if you ask me.

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Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #48 on: February 11, 2020, 01:52:20 PM »
It means you are saying 36,000 km far from earth satellite are suitable for telling out location but 1 km far from my location installed tower aren't? I have studied Architect Engineering and I know how to draw map for buildings and roads. Everything in map is benchmark to each other like one signal tower to other and so on. Now if you ask me I can draw map and create my own GPS for my city. I will draw map of my city and specify 1km=cm/inch (unit set). now I will mark each signal tower as benchmark and whoever getting signal from will be traced like how far he is from signal tower and in which direction.

That's all very well, but if something, like a hill, mountain or such gets between you and the towers, you're out of contact and cannot get your position.

So getting a signal from a position above you, which misses the landscape, would appear to be a better method.
Not Flat. Happy to prove this, if you ask me.

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Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #49 on: February 11, 2020, 01:56:36 PM »
It looks like your information is false still.

Again, GPS wasn't commercially available until 1999.

Wikipedia - https://en.wikipedia.org/wiki/Global_Positioning_System

Citation 5 - https://www.popularmechanics.com/technology/gadgets/a26980/why-the-military-released-gps-to-the-public/

"The GPS project was started by the U.S. Department of Defense in 1973, with the first prototype spacecraft launched in 1978 and the full constellation of 24 satellites operational in 1993. Originally limited to use by the United States military, civilian use was allowed from the 1980s thanks to an executive order from President Ronald Reagan[5]. "

https://www.bloomberg.com/news/articles/2014-12-04/gps-as-we-know-it-happened-because-of-ronald-reagan
Not Flat. Happy to prove this, if you ask me.

Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #50 on: February 11, 2020, 04:50:20 PM »
It looks like your information is false still.

Again, GPS wasn't commercially available until 1999.

Wikipedia - https://en.wikipedia.org/wiki/Global_Positioning_System

Citation 5 - https://www.popularmechanics.com/technology/gadgets/a26980/why-the-military-released-gps-to-the-public/

"The GPS project was started by the U.S. Department of Defense in 1973, with the first prototype spacecraft launched in 1978 and the full constellation of 24 satellites operational in 1993. Originally limited to use by the United States military, civilian use was allowed from the 1980s thanks to an executive order from President Ronald Reagan[5]. "

https://www.bloomberg.com/news/articles/2014-12-04/gps-as-we-know-it-happened-because-of-ronald-reagan
The law allowing was passed in the 1980's.

The technology allowing it wasn't available until 1999.

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Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #51 on: February 11, 2020, 04:55:53 PM »
It looks like your information is false still.

Again, GPS wasn't commercially available until 1999.

Wikipedia - https://en.wikipedia.org/wiki/Global_Positioning_System

Citation 5 - https://www.popularmechanics.com/technology/gadgets/a26980/why-the-military-released-gps-to-the-public/

"The GPS project was started by the U.S. Department of Defense in 1973, with the first prototype spacecraft launched in 1978 and the full constellation of 24 satellites operational in 1993. Originally limited to use by the United States military, civilian use was allowed from the 1980s thanks to an executive order from President Ronald Reagan[5]. "

https://www.bloomberg.com/news/articles/2014-12-04/gps-as-we-know-it-happened-because-of-ronald-reagan
The law allowing was passed in the 1980's.

The technology allowing it wasn't available until 1999.

Admittedly Mashable isn't a great source, but "on May 25, 1989, the first Magellan GPS NAV 1000s were shipped to retailers."

https://mashable.com/2014/05/25/commercial-gps-25-anniversary/
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Offline Tumeni

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Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #52 on: February 11, 2020, 05:07:57 PM »
The law allowing was passed in the 1980's.
The technology allowing it wasn't available until 1999.

"In 1989, Magellan Navigation Inc. unveiled its Magellan NAV 1000, the world’s first commercial handheld GPS receiver. These units initially sold for approximately US$2,900 each."

https://en.wikipedia.org/wiki/Satellite_navigation_device#History

So, you reckon they unveiled commercial units in 1989 but didn't get the tech until 1999? How does that work?


"Magellan was the creator of the Magellan NAV 1000—the world’s first commercial handheld GPS receiver,[citation needed] which debuted in 1989"

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


The NAV 1000

http://retro-gps.info/Magellan/Magellan-NAV-1000/index.html

See the picture of the rear panel - I may be wrong, but that looks like Copyright 1988 to me... and the serial no. 89501752
 - unit number 1752, made in May 1989?

« Last Edit: February 11, 2020, 05:13:16 PM by Tumeni »
Not Flat. Happy to prove this, if you ask me.

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Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #53 on: February 11, 2020, 08:02:50 PM »
It means you are saying 36,000 km far from earth satellite are suitable for telling out location but 1 km far from my location installed tower aren't?
No, I'm saying that the GPS (using satellites in orbit) is better suited for global positioning than the cell phone network (using towers).
Of course cell towers can be used for locating purposes and they are, check out "Hybrid Positioning": https://en.wikipedia.org/wiki/Hybrid_positioning_system

GPS has several advantages (just some examples):
  • Covering all of earth with a relatively small number of satellites instead of an enormous number of towers.
  • Covering all of earth regardless of terrain (imagine building a 1km - as you suggest - network of towers across oceans, deserts, dschungle, ..)
  • Being independent of ground installation (it was originally a military system - one usually neither relies on enemy cell towers nor does one get the chance to build own cell towers in enemy territory)
  • Providing the same quality of service and accuracy regardless of the number of users.
  • Providing a high quality of service and accuracy mostly independent of ground features. (looking "up" to a satellite without significant obstacles is in general more likely than looking "across" to cell towers in cities)
  • GPS can be used anonymously with no dependency on (specific) cell providers
  • GPS is designed explicitly and specifically for positioning
I have studied Architect Engineering and I know how to draw map for buildings and roads. Everything in map is benchmark to each other like one signal tower to other and so on.
Congratulations. I'm sure I have no talent for architecture, so when I'd need advice from that field of expertise, I'd ask experts like you.
However, this is not about drawing maps, but about electromagnetic waves, radio transmissions, signal processing, ... you don't sound knowledgeable in those areas?

Now if you ask me I can draw map and create my own GPS for my city. I will draw map of my city and specify 1km=cm/inch (unit set). now I will mark each signal tower as benchmark and whoever getting signal from will be traced like how far he is from signal tower and in which direction.
Sure, you can draw a map. You might even be able to mark all cell towers.
It will be a serious effort to correctly identify all of them and to keep that information up to date.
But load balancing mechanisms, timing issues, cell congestion, network reconfiguration, ... will constantly change performance, making your benchmarks inaccurate at best.

In 2002/2003 I shocked when I saw my town location right under time on my mobile (Samsung c220) in Pakistan. And this location was definitely took from signal towers.
Looking up the Samsung c220 I could only find one with a 2007 release date; do you have a link to your 2002/2003 version?
How do you know the location was definitely taken from signal towers?

Also if smartphones are taking location from satellite then how my Old desktop showing my location on my Google Chrome Browser?
Well if cell phones were getting their location from cell towers, how would that make any difference for your "old desktop"?

iC

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Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #54 on: February 11, 2020, 09:05:31 PM »
It looks like your information is false still.

Again, GPS wasn't commercially available until 1999.

Well, I provided one (maybe not the best) of many references, confirming the information I posted is correct, while you simply keep repeating your claim.
Humor me ... where do you get your information from and how can we confirm its validity.

Regardless, I never claimed that GPS was commercially available at the time, just that it was in place and working.
GPS has been in place and working long before cell towers were able to provide adequate positioning services for end users.

The point I wanted to make is that GPS was working well before cell phone location detection through cell towers was.
"The Gulf War from 1990 to 1991 was the first conflict in which the military widely used GPS." https://en.wikipedia.org/wiki/Global_Positioning_System#Timeline_and_modernization
Cell phone location detection was introduced in 1996.
1991 is before 1996 => The correlation you suspect between GPS and cellular network signals cannot not exist; at least not in the sense, that GPS somehow requires cell phone location detection.

Side note: How would Cell phone location detection work for US troops in the Gulf War?

iC

Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #55 on: February 12, 2020, 09:32:25 AM »
My first Post! Excuse me butting in;

I think 2 things have been overlooked here by both sides of the argument. 
 
1.  Consider the first word of the term "Commercially Available": it means you have to pay for it. 
2.  What is a GPS device. 

Looking at item 1, if I can use the analogy of old-school navigation using a paper map, then the first thing you obviously need is a map.  This means that someone has to survey the terrain and its features to an acceptable degree of precision for its intended purpose.  This might be by surveyors on the ground, aerial survey, or a mixture of both.  They then have to transfer this data onto its graphic format and organise its distribution to users.  They aren't going to give this hard-earned information away; they SELL it to the consumer.  For the sake of argument, lets call the map a database.  The second thing you need is to know where you currently are on the terrain/map.  Generally, this is a given, because we all know, depending on the journey we're making, "I'm at home", "I'm in Glasgow", or "I'm at Gatwick Airport".  Thirdly, we need a sense of direction; this might be as complex as a compass and Inertial Navigation, radio beacons, sail west at 10 knots for 6 hours, or just "walk to the church and turn left on the High Street".  Whatever, we need positional information about where we are and its relationship with where we want to be. 

Looking at Item 2; what is a GPS device?  Its got 2 parts, the first part is a receiver.  It doesn't transmit anything.  I gets free-to-receive signals from Global Positioning System satellites and by analysing differentials in the signals it determines where it is on a vast featureless ball.  This is its positional information.  It does this to a high degree of accuracy, but it has no idea that it is in Wigan.  That's where the second part comes in.  Remember our database?  We need to COMMERCIALLY buy, or rent, a database.  A true GPS device includes a software database which you paid for when you bought the GPS from Halfords or PC World or had it included in the car you bought from Honda, or the plane you bought from Cessna.  You either paid for it once at the shop, or you subscribe to an update service, but its stored in the GPS device.  Depending on need, you bought/subscribed one with your country's maps, continental maps, roads, seaways or whatever.  A SMARTPHONE is NOT a GPS device.  It EMULATES a GPS device by incorporating a GPS receiver, which (remember) does not transmit.  The PHONE transmits to a terrestrial phone-mast using your cellphone-data allowance, the network verifies your entitlement because of your (commercial) monthly data package, and sends you a map of where you currently are, from a terrestrial phone-mast.  Your phone does not carry around a database of the world, but they will RENT it to you as you need it.  If you drive into the middle of the ocean, or the desert, or probably a Welsh valley you will continue to receive a GPS signal but you will lose your phone signal, you will lose your rented maps, you will lose your emulated-GPS.  The phone's space-based GPS receiver is still working, but it no longer has a terrestrially-provided map to relate to. 


Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #56 on: February 12, 2020, 06:35:20 PM »
Not quite correct, but otherwise spot on.  If you buy a UK OS MAP it gives you a code to download the map to your phone or tablet.  The app shows your position on that map without an internet connection.

We should talk about GNSS, GPS is just the US system.  Galileo is the European one, China's BeiDou, GLONASS in Russia.

Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #57 on: February 12, 2020, 08:02:16 PM »
Thanks Inquisitive; I agree with your corrections regarding terminology, and I didn't know that about the OS Maps Apps. 

Although my argument for the existence of GPS (or GNSS) might seem logical, I confess to still being on the fence.  Of course, if its NOT satellite based, the only people who would be in on the secret would be all ships captains, all airline pilots, all marine/aviation electronic engineers, all employees of GNSS equipment manufacturers, and all national so-called space program organisations (of all geo-political persuasions). 

And why do they always install an aircraft's GNSS antenna on the top of the fuselage? 

Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #58 on: February 13, 2020, 04:53:45 PM »
It looks like your information is false still.

Again, GPS wasn't commercially available until 1999.

Well, I provided one (maybe not the best) of many references, confirming the information I posted is correct, while you simply keep repeating your claim.
Humor me ... where do you get your information from and how can we confirm its validity.

Regardless, I never claimed that GPS was commercially available at the time, just that it was in place and working.
GPS has been in place and working long before cell towers were able to provide adequate positioning services for end users.
That's true, you didn't write that.
The point I wanted to make is that GPS was working well before cell phone location detection through cell towers was.
"The Gulf War from 1990 to 1991 was the first conflict in which the military widely used GPS." https://en.wikipedia.org/wiki/Global_Positioning_System#Timeline_and_modernization
Cell phone location detection was introduced in 1996.
1991 is before 1996 => The correlation you suspect between GPS and cellular network signals cannot not exist; at least not in the sense, that GPS somehow requires cell phone location detection.

Side note: How would Cell phone location detection work for US troops in the Gulf War?

iC
Well, I haven't had the pleasure of knowing many soldiers who served in the Gulf War.

So I couldn't say.

I never wrote that GPS devices like Garmin, TomTom, or Magellan, require cell phone location devices to operate.

I surmise that signal broadcasting positions are in much the same locations as cell phone towers.

Re: How GPS Works and what about 64 satellites claimed by NASA
« Reply #59 on: February 13, 2020, 05:05:14 PM »
Have you ever sat in one spot and watched which satellites your GPS unit is seeing? If you where to do this you will see a progression of different sets of satellites. If you where to do this for long enough you will see them show up again, and in the same order. How could that happen if they were tower based?