GPS tracking

I found a set of keys (two auto keys and two fobs) on the sidewalk. I took them to the local police lost-and-found. Pointing to one of the fobs, the officer said it was a GPS tracking device. It was square, about 25mm on a side and 2-3 mm thick (about the dimensions of a US dollar coin). The officer said that the owner should be able to find it even though we were indoors. How does this work?

I know the mathematics of GPS. If this thing broadcasts its location, where does it get the electrical power to receive GPS signals let alone broadcast. I assume it has a hearing-aid batter inside. Even if it is somehow recharged by induction each evening, the battery can’t broadcast for more than a few minutes. How far can it broadcast? Is this just something for someone who forgot their keys in the kitchen next to the coffee pot?

Its called a Tile. They work via Bluetooth and communicate with phones that have the app installed. When you lose something, you activate it online and wait for someone in the “Tile community” to pass by your Tile within bluetooth range. Their phone sends a message to you telling you where your thing is. The batteries last about 12 months.

Something that small sounds more like a bluetooth tracker than GPS.

There are keychain-sized GPS trackers that actually receive GPS signals and transmit the position via a mobile phone network. The Ping is one example, battery life depends on how often it transmits the location, but it can be many days. But it’s not quite as small as you are describing (more like 1/2 inch thick). What you found is almost certainly a Bluetooth based device, as already answered.

Yep, that was it. When I googled “bluetooth tile”, the first image was one of the gadgets on the key chain.

So, does the owner have to wait until someone with the Tile app happens to go into that police station? Does the Tile fob know its location or does it depend on the phone transmitting that info back to the owner?

The Tile doesn’t know anything other than its own serial number. If a nearby smartphone with a Tile app happens to connect to it, the app reports the phone’s location to the Tile server.

Nice use of one technology leveraging another. If people are walking around with phones that can be tracked using GPS, and a short range signal from one of these key fobs is picked up…then the keyfob gets the benefit of “GPS tracking” without actually needing to have a GPS antenna etc.

This sort of reminds me of the “lite” form of GPS tracking that mobile phones sometimes rely on: cell tower triangulation. They can get their location fairly quickly (in some cases) just by measuring the relative time difference in the reception of signals from various nearby cell towers. So just stepping outside the phone knows approximately where you are, even if you’ve not had enough time for the true GPS tracking to kick in with a more accurate solution…

When I first started reading this thread, I thought the OP was going to post about actual GPS tracker devices, which decode GPS signals, then, using the mobile phone network, transmit location data to whoever is the owner of the tracker. So snoopers can track the movements of people they want to keep an eye on.

So cool! (That is, the technology shortcut, not the tracking of other people)

Even more important, nowadays, than cell tower triangulation is WiFi network triangulation. You know all those networks that you see when you check for WiFi? Google (and others) have built up maps of where all of those are, and so what networks you can see tells you where you are.