Need advice on a tracking device

[Jackie Bee]

Hi everyone! I need help. For my SciFi WIP I need to come up with some kind of a gadget that will allow two people who got separated to find each other again. Anyone knows of such technologies? It can be something that doesn't exist yet, but it must sound believable. The thing must be small and not draw others' attention. I thought maybe they have some special rings or bracelets that allow them to track each other, but I need a bit of technolgy behind this, and I have no ideas. Anyone can help?...Thanks!

 

[TitaniumTi]

Would something like the Find My Friends app fit the brief?

 

[Jackie Bee]

They don't have a phone or something... but I'll read how this app works, maybe I could incorporate this somehow. Thanks!

 

[Ray McCarthy]

Yes. There are MANY gadgets that do this. Not just phones. Usually they have a GPS receiver.
Just say that they have trackers.
Ham / Amateur radio people have APRS, sometimes in sets as small as a phone. There are licence free two way radios with GPS that do this. One brand can use Bluetooth to link to phone to give additional information.
ANY mutual tracker (not running on magic) will always need three ingredients. There is NO physical way round it:
1) A radio receiver for navigation signals (GPS or similar), OR much larger power hungry inertial navigation system OR manual input from map reading. A cruise missile has all three of these, with camera to track real ground and compare to map.
2) Radio transmitter to send your position.
3) A second radio transmitter to receive your position.

If it has any range with out a phone base station to connect (phones are ALL short range, using base stations to connect to fixed infrastructure) then it will have large aerial and large battery.

If it's the size of large bulky bracelet (tracker on a criminal, usually ankle), then it's using phone base stations. If it's smaller, then it's using a local WiFi point. None of this is going to change much with any new technology as we are at the limits of physics already.

 

[The Judge]

Scent-detection devices, if one of the characters knows (nose...) where the other has been so can follow a trace, like a sniffer dog. The great advantage of that (which I've used in my SFs) is that you can manipulate its use, so if you want one of them to be truly lost, the sniffer won't work if they don't have a starting point, or if, say, the character was abducted in a van.

At present it's very much a handwavium device, and certainly getting it down to a moderate size is likely to be a problem, but if nature can do it with a dog's nose, I can't see why science can't come up with it eventually -- whether time and money would be spent on developing the technology when it's cheaper and easier to train dogs is another matter of course.

 

[Jackie Bee]

Yes. There are MANY gadgets that do this. Not just phones. Usually they have a GPS receiver.
Just say that they have trackers.
Ham / Amateur radio people have APRS, sometimes in sets as small as a phone. There are licence free two way radios with GPS that do this. One brand can use Bluetooth to link to phone to give additional information.
ANY mutual tracker (not running on magic) will always need three ingredients. There is NO physical way round it:
1) A radio receiver for navigation signals (GPS or similar), OR much larger power hungry inertial navigation system OR manual input from map reading. A cruise missile has all three of these, with camera to track real ground and compare to map.
2) Radio transmitter to send your position.
3) A second radio transmitter to receive your position.

If it has any range with out a phone base station to connect (phones are ALL short range, using base stations to connect to fixed infrastructure) then it will have large aerial and large battery.

If it's the size of large bulky bracelet (tracker on a criminal, usually ankle), then it's using phone base stations. If it's smaller, then it's using a local WiFi point. None of this is going to change much with any new technology as we are at the limits of physics already.

Thanks, thats a lot of usefull information! It gives some direction. I'll need to learn more to use it...

Scent-detection devices, if one of the characters knows (nose...) where the other has been so can follow a trace, like a sniffer dog. The great advantage of that (which I've used in my SFs) is that you can manipulate its use, so if you want one of them to be truly lost, the sniffer won't work if they don't have a starting point, or if, say, the character was abducted in a van

That's an interesting idea, but would't fit my storyline--thanks, anyway!

 

[Ray McCarthy]

but if nature can do it with a dog's nose, I can't see why science can't come up with it eventually

Even if it's like the poor cockroach add on kit sold to schools, to remote control a real cockroach (really why is this allowed be marketed as "Educational" for schools?). Maybe dogs with a bluetooth implant and app.

The other "tracking" option that's possible (though currently dangerous, but in future perhaps engineered more safely) is Radioactive tracers. Like scent it is only a trail. With scent or radioactivity you have to "cross" the trail. The Radio based systems can work world wide with no knowledge of any part of trail.

Unlike an electronic nose (small ones exist for particular chemicals already*), a radiation detector is already compact and operates down to background radiation levels. An implant on shoe (possibly covertly) can leave a radioactive trail. This might not be very healthy in long term for the tracked subject, I'm not sure though. It's currently used to find pipeline leaks and cracks etc. Looking for soap bubbles is only practical on your home gas pipe

[* Carbon Monoxide, LPG are common. Ones for drugs and explosives are not as good as dogs yet. I suspect Nitroglycerine (the active part of dynamite) can be detected with electronic nose. But you need to detect a wide range of materials. Compact & affordable outside a lab electronic "noses" tend to detect a limited range of similar compounds, each.]

 

[Loren]

I was thinking of a compass and a map.

The only requirement are knowing where you are and how to read a compass and a map. Tricky stuff for many people as they haven't seen a compass and are clueless with maps.

You might want to research military systems for determining positions of troops and equipment. This is an important factor for armies and they employ a wide variety of tools.

Barring magic, here are some of the basics:

GPS provides a reliable means of position where reception is good. There are variants called wide-area-augmentation that use land based transmitters at known locations. Cell phone towers act in this way by a form of triangulating your position based on comparing their clocks with the clock in the cell phone you carry, much like GPS. This tells your position, but doesn't tell other people's position. That information needs to be transmitted to the interested parties.

Whether you use cell phones or a dedicated GPS receiver, both methods rely on a system to be implemented. For GPS it is a constillation of satellites and for cell phones it is a large number of cell towers at known locations.

iPhones handsome other cell phones use both systems.

As far as individual off-grid location, the only other option (besides dead reckoning) is really radio and some form of directional antennas that allow you to find the direction of the other transmitter. This tells you little about the distance since signal strength alone can vary for any number of reasons. You are also pretty limited with radio range. The frequency of the radio is one factor. Long wavelength like AM radio travel far, but are not very directional. Short wavelength like VHF, UHF, and microwave are very directional, but limited by obstructions.

Radio can also be spoofed by something called multi-path signals. These are signals that bounce off of obstructions and appear to come from a different direction.

Lastly, dead reckoning is a form of knowing where you were and what direction you set out on. Essentially, you keep a detailed record of both your direction and distance and every time you change direction you make note of that. These are called vectors and when mapped out will tell you where you are relative to where you started.

Something as simple as a compass and counting paces can provide dead reckoning, but for two people to know each other's positions they must also be in communication with each other.

"Marco!"
"Polo!"

 

[Loren]

Scent-detection devices, if one of the characters knows (nose...) where the other has been so can follow a trace, like a sniffer dog. The great advantage of that (which I've used in my SFs) is that you can manipulate its use, so if you want one of them to be truly lost, the sniffer won't work if they don't have a starting point, or if, say, the character was abducted in a van.

At present it's very much a handwavium device, and certainly getting it down to a moderate size is likely to be a problem, but if nature can do it with a dog's nose, I can't see why science can't come up with it eventually -- whether time and money would be spent on developing the technology when it's cheaper and easier to train dogs is another matter of course.

Scent is an important mechanism for tracking, but very unreliable due to weather and a host of other environmental conditions.

It doesn't exactly tell you where someone is, but allows you to follow a path that should lead to their current position.

All bets are off if the individual gets in a car/motorbike, bicycle, boat, or aircraft.

 

[Nick B]

If the 'security' agencies had their way we'd all have RFID chips right now. The tech is available right now. I reckon give it a decade and they will be compulsory.

 

[Loren]

If the 'security' agencies had their way we'd all have RFID chips right now. The tech is available right now. I reckon give it a decade and they will be compulsory.

The ability to actually track people is almost impossible with RFID.

The maximum distance over open ground is about 600 meters. It will be considerably less in cities and buildings.

That means you need to have a HUGE number of transceivers scattered everywhere. It also means you need a HUGE infrastructure to sort out the millions and millions of individuals among the myriad of transceivers.

Of course there also needs to be a huge network of service people to maintain the system as well as a huge number of operators just to organize and maintain the database.

The cost of that kind of surveillance would be astronomical and the payback relatively small.

 

[Ray McCarthy]

Tracking with RFID is impossible. Needs REALLY bulky gear for more than 3m!

A shopping mall where EVERY shop has it at the door is a privacy / tracking issue.

An RFID tag is passive. It's also pretty dumb. It's powered by the terminal's transmitter, hence poor range. It's essentially not much more than a memory device, simple CPU and an aerial. No location ability, other than the Terminal is at a known location and the RFID is unique. It's really a wireless replacement for a barcode, invented for warehouses (and totally stupid security fail for oyster or other travel cards, passports, retail products and plastic payment cards)

 

[Jackie Bee]

Wow, I can see that some people here really understand this kind of things. Maybe you can help me make up a couple of sentences that would sound true, because that's basically all I need? Something like "Mike turned on his tracker - a small, watch-sized device that used __________ to show the direction and the distance to another tracker, given its identification number", or something like that. What would you use to fill the blank?

 

[Nick B]

Not all rfid tags are passive. Also the readers dont have to be bulky, they can be hand held, such as the type used to identify a tagged pet.
Ranges of up to 69 feet have been recorded.
Also, the gps chips used in smart phones are small enough to implant. And you can download apps that can track them from app stores.

So in answer jackie, yes, a watcg is plenty big enough to house either a tracking device, or the device doing the tracking.

 

[Nick B]

The words for the blank are - global positioning.

 

[Ray McCarthy]

Not all rfid tags are passive.

Then it's not a real RFID tag.
By definition all RFID tags require external power, that's what I mean by passive. They do have a CPU and memory, they can't activate on their own, only when powered by an external RF source, a transmitter. Only anti-theft tags without any ID are 100% passive in sense of ONLY being a tuned aerial (dipole for microwave or loop for shortwave tags). ALL RF ID are passive in sense of having no internal power, or else it's not an RFID tag.

Of course regular readers are compact. Only "spying covert" RFID tag readers are bulky as they need a large aerial to direct the signal and pick up the weak tag signal.
The technology is over 40 years old (not disposable then). It's just that it's now cheap enough for disposable/retail and more capable.

gps chips used in smart phones are small enough to implant.

Power and aerial and CPU would be an issue. The chip alone are small enough to implant. But an entire viable GPS receiver, no. Possibly never. Physical limitation on aerial size and efficiency, even if you solved the power issue.
Then you need a CPU and transmitter and aerial. The Transmitter about x10 to x1000 more power consumption depending on range.
I've been designing this sort of stuff since 1980s, so I know the difference between bits that can be miniaturised and bits intrinsically that that can't (like aerials, filters and transmitter power supplies).

Ranges of up to 69 feet have been recorded.

Depends PURELY on power and terminal aerial. Only 3m max (if lucky) for a standard compact terminal. A lot further than 69 feet (I forget exact figure) with a custom spying rig. But no use as said earlier for a "Tracker". You need GPS receiver (GPS is the US system. There are at least three Global Positioning systems using satellite and still one terrestrial system). The Trackers need separate transmitter / receivers to communicate. Anything other than Mobile phone mast system needs large aerials and a LOT of power. You can get gadgets with mobile phone type transmitter/receiver and GPS receiver and aerials all self contained. Some cars and trucks use them. The control centre gets position via mobile phone network and they can then remote control the vehicle. There was an issue with Jeeps that had really no security on it.

It's also possible to workout position using the timing of two FM radio signals via the RDS (same in States as Europe, but they call RDS something else). GPS doesn't work indoors unless you are at a window. FM radio does. Some WiFi chips used in routers are designed for phones so have an FM Radio chip. It's been proved that custom SW can be added to the router to calculate position, this works indoors. Then via WiFi any gadget using this chip and cpu could work as a two way tracker. Even today this can be disguised as functional wrist watch (need charged every day). Shorter range than the phone module solution but smaller, works indoors (Global Positioning /GPS doesn't really), less power.
You can of course combine BOTH approaches in a bracelet (or large watch) type gadget. Perhaps in the future it might have better battery life and smaller. One GPS module (includes aerial) I have is pretty tiny, I also have Wifi + Mobile Phone module with battery that's only about x4 size of a watch. I think using Open WRT version of Linux it could work as two way tracker with watch face doubling as direction and distance indicator.

2006 I adapted a desktop router to work on batteries because it had a PCMCIA slot. We then put in an early experimental 4G laptop card to make a portable 4G WiFi hot spot. It was about the size of a large paperback book. Now these are available in the local phone shops and 1/2 the size of a small mobile phone with 2G/3G/4G modem and WiFi.

 

[psychotick]

Hi,

Not sure why your people don't have phones. Everyone else seems to these days (except me). But failing that and considering that it's sci fi, why bother with the details? Assume these people have chips implanted - a little bit more advanced than a simple RFID. They're talking about doing this now by the way - chips that will hold the details of your credit cards, perhaps be implanted in your hand, and which will let you pay for goods simply by waving your hand sans card, over the reader.

Now assume that these chips send out signals keyed to an individual frequency constantly, so they are RFIDs I suppose, but with a permanent power supply (nuclear battery?) and that everyone can be found wherever they are - no satellites or GPS needed. And the tracker device is actually a future style watch - it just has a tracker function. Push a button or speak a command and the tracker function switches on and replaces the hands. Then enter the individual frequency of the chip / person you want to find, and it gives you a pointer hand and an estimated distance to target based on signal strength. Then you just get in your car and drive in that direction, following the watch.

Cheers, Greg.

 

[Loren]

Hi,

Not sure why your people don't have phones. Everyone else seems to these days (except me). But failing that and considering that it's sci fi, why bother with the details? Assume these people have chips implanted - a little bit more advanced than a simple RFID. They're talking about doing this now by the way - chips that will hold the details of your credit cards, perhaps be implanted in your hand, and which will let you pay for goods simply by waving your hand sans card, over the reader.

Now assume that these chips send out signals keyed to an individual frequency constantly, so they are RFIDs I suppose, but with a permanent power supply (nuclear battery?) and that everyone can be found wherever they are - no satellites or GPS needed. And the tracker device is actually a future style watch - it just has a tracker function. Push a button or speak a command and the tracker function switches on and replaces the hands. Then enter the individual frequency of the chip / person you want to find, and it gives you a pointer hand and an estimated distance to target based on signal strength. Then you just get in your car and drive in that direction, following the watch.

Cheers, Greg.

If you want physics to support your premise, then you are going to need to sprinkle the planet with literally zillions of transceivers to track RFIDs (Radio Frequency IDentification).

As Ray said, the physics of antennas and RF power requirements are going to be the limiting factors.

We are only talking about a system that identifies people's current position, but the other half of the equation is sending someone else's position to you! That's another can of worms far beyond RFIDs.

 

[Jackie Bee]

Not sure why your people don't have phones. Everyone else seems to these days (except me).

It's not nowadays, the story is post-apocalyptic Mad Max kind of reality.

And the tracker device is actually a future style watch - it just has a tracker function. Push a button or speak a command and the tracker function switches on and replaces the hands. Then enter the individual frequency of the chip / person you want to find, and it gives you a pointer hand and an estimated distance to target based on signal strength. Then you just get in your car and drive in that direction, following the watch.

Yes, I guess I'll go for some kind of such a watch without explaining too much...

 

[Ray McCarthy]

Then enter the individual frequency of the chip / person you want to find, and it gives you a pointer hand and an estimated distance to target based on signal strength.

Max range about 2km
More distance than that needs infrastructure or massive power (which makes you vulnerable to ANYONE tracking you)