fandomsecrets | [ SECRET POST #3485 ]

[ SECRET POST #3485 ]

⌈ Secret Post #3485 ⌋

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Okay, I'm writing a fic where a character gets taken hostage, and ideally, I don't want her to be able to be immediately found by cell phone tracking. So my question is sort of multi-layered. Also, assume the character is FBI, and her boss wouldn't hesitate to immediately trace her cell phone, with the immediate FBI access that brings. First part of the question is, how does the kidnapper need to destroy the cell phone, what in it needs to be gone to make it unlocatable? Assuming it's a smart phone, is it easier to smash it and remove a chip (and then destroy the chip?), throw the phone in water, or blow it up in the microwave (said kidnapper would be more than happy to do this, and does not need his microwave)? All are options, but most importantly, the phone needs to be destroyed on the spot, as the kidnapper does not currently have the option of leaving the building or throwing the phone from a moving vehicle, etc. Second question is, after this is done, and the cell phone is later traced, what is that location based on? The place the last call was made, the last ping from a tower when the character used messaging or email, what? If the character hadn't used her phone in an hour (and that hour ago was when she was elsewhere), and the phone is now destroyed, there's no way a trace could lead right to her location, is there? I am trying to cover this from all angles, lol.

AT&T Wireless customer service training to the rescue!

Honestly, if you've powered off a cell phone, there isn't an invisible way for cell companies to track you. If you have a device that doesn't have a GPS system, it will be impossible to pinpoint someone's exact location other than a general proximity of which cellular tower they connected to last.

Depending on the network, those towers are often 10-15 km apart. More if it's a rural area and less coverage is necessary.

Edit: This is why it's important to state the time period your story takes place in. Almost all devices have GPS these days. Many people don't turn theirs on, and if that's the case there isn't really a way to instantly know exactly where a person is. In certain countries (Korea, I believe?) cellular network providers can actually remotely access the GPS on some devices in order to turn them on in case of emergency, but this doesn't generally apply to all models of mobile devices.

You don't need to smash anything. You don't need to remove chips. That is pure movie bullshit. All a kidnapper would need to do is to turn off the cell phone and leave it on the ground.

Edited 2016-07-19 23:17 (UTC)

OP.

See, TV has lied to me this whole time! What with everyone snapping phones in half (Breaking Bad) or stomping on them. Everyone is always destroying cell phones.

>This is why it's important to state the time period your story takes place in. Almost all devices have GPS these days. Many people turn theirs on, and if that's the case there isn't really a way to instantly know exactly where a person is.

But if you regularly left your GPS on? Would turning off the phone still make it untraceable? Stupid question: if GPS was on, would you be able to track the phone to the last location the phone was on in, or just the last location/tower the phone was actually used in?

As for time period, that's the tricky part. It technically takes place a few years in the future, so I can only extrapolate on what current cell tech is. And not that I really expect readers to be thinking about what cell phones several years from now will be like, I just want it to be as realistic as it can be.

You break a chip to try to get rid of any data that might be recovered from a cell phone. If you have incriminating pictures or saved numbers or a network of co-conspirators, it is in your best interests to destroy a phone. This is why you see criminals doing things like that.

Unfortunately for criminals, cellular network providers will keep records of incoming and outgoing calls, texts, and data specifically for providing to law enforcement. If you have an unregistered phone number, however, the law enforcement would first have to extract the number from the device itself in order to get those records.

If you regularly leave your GPS on, it will be continually transmitting to whichever satellite network it is hooked up to. You will be able to see the last known street address, intersection, or section of highway. It's basically like the FBI would have a google maps layout of the last known location. It doesn't keep working after a phone is turned off. There is no data transmission happening after a device is powered down.

Even a few years in the future, there is likely not going to be an option of continuing GPS tracking after a cell phone is powered down unless there are some extremely lucky circumstances. The only thing I can really suggest is that in the future cell phone GPS satellites (which are usually private and accessible by law enforcement agencies only via warrant) may no longer be considered private. If you are going for a totalitarian feel, it's reasonable to suggest that CIA/FBI spy satellite networks may force instant access to GPS satellite streams.

Currently, the best available tracking schemes for spy satellites rely on a technician to positively identify a target using a combination of facial recognition software and operator training. Under ideal conditions they are as good as google street view, but as you might suspect, weather conditions can obscure even the best attempt at finding someone. This is not likely to change in the future, but in the future facial recognition technology will only improve.

That's something for you to consider at length.

Thank you very much! This helps a lot!

I suppose I also have the option of my character being in an area without coverage, since she's going to be in rural area quite out of the way. I know coverage lapses are slowly disappearing, but it depends what carrier you're with. I know places where I don't get reception.

Oh there's still a surprising amount of zero coverage areas depending on which country this is set in. Way more than the companies want to admit, really.

The thing is though, you don't need a cell tower for GPS to work. You need a steady connection of transmission with that satellite. It does work better if you can bounce off a tower, but your average device may be able to pick up a GPS signal even out in the middle of absolutely nowhere. Usually the range of coverage for satellites is on the order of thousands of miles.

Hmm, good to know.

GPS doesn't work that way. "Bouncing" a GPS signal off a tower would defeat the entire purpose of the system since the calculations depend on "straight" line of transmission from satellite to receiver, knowing exactly where the satellite was at the time of transmission, and calculation of differences between time code due to the speed of light.

And yes, you can pick up GPS in the middle of nowhere (including antarctica), because that's what it was designed to do.

These days cellular towers have inbuilt satellite uplinks for exactly the purpose I was describing, friendo.

Granted, it's not quite correct to call it bouncing a signal because there's no relay happening so much as there is triangulation happening.

You can triangulate using ground networks just the same as you can triangulate using an orbital network, and there is often communication between the two! Surprise! Cellular service these days is more complex than having an untethered GPS unit like you would find in the 00's.

These days cellular towers have inbuilt satellite uplinks for exactly the purpose I was describing, friendo.

Which have nothing to do with GPS. Again, GPS requires 1. accurate data about the satellite's position, 2. straight-line transmission from satellite to receiver, and 3. measurement of minute timestamp differences due to the speed of light. All of which are incompatible with the use of a satellite relay. (There are ground-based GPS transmitters for millimeter-precision measurement, but consumer products can't use them.)

You can triangulate using ground networks just the same as you can triangulate using an orbital network, and there is often communication between the two! Surprise! Cellular service these days is more complex than having an untethered GPS unit like you would find in the 00's.

Ground networks have nothing to do with GPS. Except for control signals, (which you wouldn't have access to because GPS is still a military technology and they don't like it when you set their property spinning for the lols) GPS is a one-way transmission from satellite to receiver. It doesn't require a transmitter, and it works on devices that don't have an active data connection. Standalone GPS systems are still produced and used because they're reliable, don't add data charges, and can be used for nautical and aviation applications where you need specialized maps and displays.

Now if a device is communicating GPS data, (latitude, longitude, and altitude rather than street address) it's doing so via other network protocols. It's not using GPS to do so. The statement, "If you regularly leave your GPS on, it will be continually transmitting to whichever satellite network it is hooked up to." That's about like saying that if you use the FM receiver on your phone it will be continually transmitting to Bob and Tom.

If you regularly leave your GPS on, it will be continually transmitting to whichever satellite network it is hooked up to.

GPS doesn't work that way. GPS satellites send a synchronized time code from a highly stable orbit. The GPS receiver reads the time codes from multiple satellites, calculates the difference between time codes, uses that to calculate distance to each satellite, and does some complex trigonometry to calculate the location of the receiver on the Earth.

No data goes from GPS receiver to GPS satellite. This is important for military applications, and most handhelds can't get into orbit anyway because they lack the power or antenna to do so.

Now if you're using something like the Google Maps API, you'll be transmitting GPS data nearly continuously through the ground-based cellular network and getting map updates. However commercial GPS systems usually have the maps pre-loaded into memory so they work reliably without cell phone coverage.

Privacy tinhatters suspect that many phones can be activated remotely and silently. But removing the battery is probably sufficient.

Another method of triangulation is to use raw cell tower data to triangulate a rough position. It's not as good as GPS but is good enough for military work.

Same person, back to bug you, lol. For the same situation in the same fic.

If a call is made (to a questionable person) from a character's cell phone, how much can someone actually know about the call? If the cell phone is not actively being tapped (which it isn't) there's no way for anyone to hear the actual conversation, is there? And if the character's cell phone is traced in order to find their location, that's just a GPS ping, right? To actually get a record of calls made from the phone, you would need, what, a warrant? Though given that this character is missing and is in law enforcement, a superior might bend the law to get whatever they could get without a warrant. But once you had a call record, is it possible to trace the other phone's location just based on its number?

Well, I'm not sure about what the NSA actually has legal access to in a given situation, but theoretically you could listen to someone's cell phone call from a specific number as the call is being made. It's all digital. It's the same as receiving a radio signal in real time; wire tapping phones has actually gotten easier, not harder.

You would just have to wait for that number to show up on the network and if someone was waiting for it, they'd be able to listen in to whatever was being said.

Okay, thanks!

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[ SECRET POST #3485 ]

Question about tracking cell phones

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