In order to not "start from scratch", though, you will need to save some state persistently about your location (and the location of the satellites), which will cost power. Then you go in a building and lose all your signal, while still burning power to maintain that old state.
If it was that easy and cheap in terms of power, AirTags would have GPS receivers. They don't.
Flash memory preserves data without using any power at all. Ditto EEPROM. Both present in even the most basic of embedded processing cores (and the GPS protocol is implemented on those)
You need to move quite the distance for a GPS device to need to change just one satellite, much less all 3 and it doesn't matter if you've been underground or not as the thing will just try first the ones in its memory and unless you travelled hundreds of km underground, it's still going to be the same 3 satellites.
Last but not least, AirTags use CR2032 batteries with a capacity of around 200mA/h - 1/20th of a mobile phone one - and that charge is supposed to last for years between battery changes, not a mere few days until the next time the phone is charged. The power consumption of an AirTag must be thousands or even tens of thousands of times lower than what we've been talking about, in the order of nano-amperes not tens of milliamperes.
You're clearly clinging on to that pre-conception of yours for reasons other than logic, and you keep on inventing wild theories based on zero domain knowledge, to try and justify that beloved pre-conception of your, so I'll leave you to it since this feels like trying to explain that the Earth is roughly spherical to a Flat Earth believer.
You seem to be the one going through mental gymastics to justify why the button might not just turn the thing off. Sometimes they're not out to get you, you know.
These phones cram oodles of stuff into a tiny space at super low margins , and are perfectly good at spying on their users when turned on. There's no reason for them to spend any extra effort to spy when they're turned off, for the .01% of people who turn their phones off regularly.
The margins aren't as low as I thought, but they still aren't giving any money away on their BOMs....
Let me explain this in a very very simple way: buttons which are not literally mechanical switches that physically connect and disconnect from power require that at least some of the circuitry to be alive because they're capacitive contacts, a technique which requires some power and some logic to detect that the button has been pushed.
So even shitty shit $0.12 microcontrollers often come with support this stuff, so that they can generate a hardware interrupt in the microcontroller to wake it up when a user presses one such soft button to power on a device.
Beyond this, in order to support something as simple as wakeup from the network side - for example, to support Find My Phone functionality - even $3 microcontrollers (not microprocessors, microcontrollers, their cheap cousins with puny computing power) have features such as programmable secondary low power cores that consume tiny amounts of power.
Even this "advanced" stuff doesn't add cents to BOMs, it only adds tiny amount of extra surface on vastly more complex microchips, which translates to at most tenths of a cent of extra cost because this stuff isn't supposed to be decoding videos or running some social media user interface (or any user interface), it's just running small simple programs which might use a few peripherals configured to remain active in low power mode (and those can be network related) to listen for certain conditions and decide if it should wake the main cores up or not.
The functionality isn't there in the hardware because they added it to facilitate spying, it's there because that's just the direction the technology evolved in the last 2 decades - soft buttons instead of mechanical ones, some amount of always on functionality for fast start, support for convenience features for users, that require some kind of wake up from the network side or merelly because microprocessor or SoC makers add everything and the kitchen sink to their designs to try an make that chip usefull for the broadest list of use cased possible (it's quite insane the amount of stuff built-in in even the cheaper of the the current generation of SoCs) so that those chips are used in more devices and get sold more.
But it gets better: none of this is necessary:
Hacked phones just simulate shutdown. They don't even go into low power mode, they just show the user a fake shutdown animation and keep on running at full power.
Now, maybe somebody who has never been involved in Politics, or Demonstrations, or Strikes can go around with total confidence that their phone ins't hacked, but if you're anywhere close to the organisers of the kind of public demonstration that can snowball into to the current POTUS losing an election, don't assume your phone hasn't been hacked (which can be done remotelly) and that turning it off in the soft button marked power when you go into a meeting with other organisers has actually in fact fully turned it off in a way that makes sure it isn't spying on that meeting.
In order to not "start from scratch", though, you will need to save some state persistently about your location (and the location of the satellites), which will cost power. Then you go in a building and lose all your signal, while still burning power to maintain that old state.
If it was that easy and cheap in terms of power, AirTags would have GPS receivers. They don't.
Flash memory preserves data without using any power at all. Ditto EEPROM. Both present in even the most basic of embedded processing cores (and the GPS protocol is implemented on those)
You need to move quite the distance for a GPS device to need to change just one satellite, much less all 3 and it doesn't matter if you've been underground or not as the thing will just try first the ones in its memory and unless you travelled hundreds of km underground, it's still going to be the same 3 satellites.
Last but not least, AirTags use CR2032 batteries with a capacity of around 200mA/h - 1/20th of a mobile phone one - and that charge is supposed to last for years between battery changes, not a mere few days until the next time the phone is charged. The power consumption of an AirTag must be thousands or even tens of thousands of times lower than what we've been talking about, in the order of nano-amperes not tens of milliamperes.
You're clearly clinging on to that pre-conception of yours for reasons other than logic, and you keep on inventing wild theories based on zero domain knowledge, to try and justify that beloved pre-conception of your, so I'll leave you to it since this feels like trying to explain that the Earth is roughly spherical to a Flat Earth believer.
You seem to be the one going through mental gymastics to justify why the button might not just turn the thing off. Sometimes they're not out to get you, you know.
These phones cram oodles of stuff into a tiny space
at super low margins, and are perfectly good at spying on their users when turned on. There's no reason for them to spend any extra effort to spy when they're turned off, for the .01% of people who turn their phones off regularly.The margins aren't as low as I thought, but they still aren't giving any money away on their BOMs....
Let me explain this in a very very simple way: buttons which are not literally mechanical switches that physically connect and disconnect from power require that at least some of the circuitry to be alive because they're capacitive contacts, a technique which requires some power and some logic to detect that the button has been pushed.
So even shitty shit $0.12 microcontrollers often come with support this stuff, so that they can generate a hardware interrupt in the microcontroller to wake it up when a user presses one such soft button to power on a device.
Beyond this, in order to support something as simple as wakeup from the network side - for example, to support Find My Phone functionality - even $3 microcontrollers (not microprocessors, microcontrollers, their cheap cousins with puny computing power) have features such as programmable secondary low power cores that consume tiny amounts of power.
Even this "advanced" stuff doesn't add cents to BOMs, it only adds tiny amount of extra surface on vastly more complex microchips, which translates to at most tenths of a cent of extra cost because this stuff isn't supposed to be decoding videos or running some social media user interface (or any user interface), it's just running small simple programs which might use a few peripherals configured to remain active in low power mode (and those can be network related) to listen for certain conditions and decide if it should wake the main cores up or not.
The functionality isn't there in the hardware because they added it to facilitate spying, it's there because that's just the direction the technology evolved in the last 2 decades - soft buttons instead of mechanical ones, some amount of always on functionality for fast start, support for convenience features for users, that require some kind of wake up from the network side or merelly because microprocessor or SoC makers add everything and the kitchen sink to their designs to try an make that chip usefull for the broadest list of use cased possible (it's quite insane the amount of stuff built-in in even the cheaper of the the current generation of SoCs) so that those chips are used in more devices and get sold more.
But it gets better: none of this is necessary:
Now, maybe somebody who has never been involved in Politics, or Demonstrations, or Strikes can go around with total confidence that their phone ins't hacked, but if you're anywhere close to the organisers of the kind of public demonstration that can snowball into to the current POTUS losing an election, don't assume your phone hasn't been hacked (which can be done remotelly) and that turning it off in the soft button marked power when you go into a meeting with other organisers has actually in fact fully turned it off in a way that makes sure it isn't spying on that meeting.