Does your phone truck you?

We get in the car, enter the address of the building we want to go to into the app, then comfortably drive to our destination with our favorite music. We are guided by our smartphone which knows our location and the exact route to our destination. Nothing unusual for the 21st century.

  • But how does our phone know our location?
  • Does it use a single technology for this purpose or multiple?
  • And most importantly, what price do we actually pay for this luxury of navigating us to our destination?

Our location is a very valuable piece of data because it tells us a lot about us. Based on it, our habits and preferences can be determined quite precisely. There are several technologies for tracking smartphone owners, the possibilities for getting to know us and using this data are quite formidable. Let’s take a look at all the methods our phones use to track our location.



Let’s start with the most obvious method of tracking our smartphone’s location, which is GPS. The Global Positioning System was introduced in the 1970s to allow the U.S. Department of Defense to determine location in real time. Every modern smartphone is equipped with a radio wave receiver operating at GPS frequencies. For the system to work properly, our smartphone must be in range of at least four GPS satellites and receive the radio waves they transmit. The satellite knows its exact location and the time it is transmitting a message through these waves. Knowing the time when the satellite broadcasts a message, its exact location at that time and the propagation time of the waves, one can determine the distance of the receiver, i.e. our smartphone, from the satellite. With at least four such distances, it is quite easy to calculate longitude, latitude and ellipsoidal altitude. In other words, basically all we need to calculate our location to the nearest meter is the message received from the four satellites. I point out here that our smartphone only receives and interprets signals that are available almost anywhere on the earth’s surface. There are currently dozens of GPS satellites orbiting the earth, so there is no concern that we will not be in range of at least four unless we are shielded by buildings. Despite its age, GPS is still one of the most accurate and efficient location systems. I have encountered a few times the wonder why, when boarding a plane and turning on “airplane mode,” the phone still knows the location. Well, “airplane mode” in our smartphones only disables reception and transmission on cellular network frequencies and sometimes wifi and bluetooth. It has nothing to do with GPS. For that matter, if our phone has “airplane mode” turned on but as a device is running all the time, it can still collect data from satellites and determine location. Once it has landed, when it has access to the Internet, it might as well make all the stored history available to the applications to which we have provided location services for review. Turning on “airplane mode” really only blocks the ability to download the digital map against which that pretty dot representing our location is displayed in our navigation app. Locating us by GPS can only be turned off if we toggle “location services” in our phone’s settings. Then only our phone will stop receiving radio waves from GPS satellites.

Cellular network

The apps we use quite often ask us to access our locations in order to monetize this data. Ad providers know that GPS may not work well in underground buildings or those with very thick walls. And this is where another method of tracking our location comes to the rescue – cellular networks. Every phone has an IMEI number, or International Mobile Equipment Identity. The IMEI number is unique to every mobile device in the world, regardless of the company that manufactured such a device. In addition, each SIM card has a unique IMSI number, or Internationa Mobile Subscriber Identity. In order for a phone to work properly, that is, to actually be able to call someone, it must connect to a mobile base station. Probably each of you has seen more than one telecommunication station with several or more than a dozen antennas pointing in different directions. This is the base station. Sometimes in our range is one such station, and sometimes several. In order for a phone to make a call, it must continually check how many base stations are in its range. For this it regularly sends its IMEI and IMSI into the air every second to let the base stations know it is in range. Each base station in range responds so that you can determine which one is closest. The message on each of these base stations remains, “a device with this IMEI and this IMSI was nearby during these hours.” But as if that wasn’t enough, our location can be determined using so-called triangulation. If we are able to determine the distance to the phone based on the signal strength from a given station, then with data from three such stations using simple geometry we can determine a fairly precise location. We know the exact location of the base stations and we know the distance of the phone from each of them. Thus, having the data on the location of the base stations and the history of IMEI and IMSI IDs sent, it is possible to reconstruct with a fairly high degree of accuracy where the phone was and at what time. Both the phone can keep a history of base stations visited, and the mobile network operator must at least some time keep a history of phones logged into base stations. Does either the phone manufacturer or the mobile network operator monetize the locations collected? Just to reiterate, this is quite valuable data, as it reveals our consumer habits. Knowing what places we visit can learn about our interests and suggest relevant advertising or offers.


Sometimes cell phone coverage can also fail, but this is not a problem for today’s technology. There are still other methods of locating devices. WiFi is one of them. Just as IMEI and IMSI in cellular networks are unique identifiers for the device and SIM card, so for WiFi such identifiers are the MAC address and BSSID, or Basic Service Set Identifier. If we are walking through the city with our phone and have WiFi turned on then we may not even connect to any router, but our phone, all the time will scan the nearby space for an access point. Our phones, in order to locate the nearest access points (i.e. wireless routers, for example), continually send their unique MAC number out into the world. If an access point receives such a message, it will respond with its unique BSSID. The BSSID is also routinely sent out into the space without prior request, if the default settings have not been changed. Walking through the city, we may come across dozens or even hundreds of such access points. Our phone can store the entire history of points found and make it available to installed applications. Such data later combined with data from GPS and mobile networks are geographically merged and global maps of WiFi access points are built. Such global maps contain all the information that was gathered by simply listening to communications between smartphones and access points even if they were not connected. They were merely trying to see what was around them. Global maps of access points are updated all the time. You can find some online and view them for free. So again, by having a history of nearby access points that we passed while walking, we can be located with great accuracy. The more access points we passed, the more accurately we can be tracked.


Bluetooth is another very useful tool for locating us. Wireless headphones, watches or other devices are indeed very convenient. However, in some ways, Bluetooth works just like other wireless networks. As soon as we turn on bluetooth on our device, it immediately starts sending information to the world about our phone model and unique MAC address, among other things. Yes, bluetooth also has its own MAC address, just like WiFi. Such a signal can be received by anyone, even an ordinary passerby, who also has Bluetooth on and doesn’t even need to connect to us. Bluetooth 5.1, as one of the latest standards of this technology, is capable of locating devices with centimeter-level accuracy. No wonder that in hotel buildings, shopping malls and other large facilities sometimes special bluetooth beacons are installed, which constantly scan the environment for nearby devices. Such data is sent to servers with high computing power and further processed for various purposes. Isn’t the information about all the stores visited and the time spent there a gluttonous morsel for the owner of a shopping center chain? If we have an app of a given shopping center, we can receive notifications about discounts on potentially interesting products precisely on the basis of the data collected in this way. Admittedly, bluetooth can be turned off quite easily. This will involve the loss of connection to wireless headphones, but on some phone models bluetooth will still send its identifiers out into the world. So you also need to disable bluetooth scanning in slightly deeper settings to actually prevent this from happening.

Ultrasonic Cross-Device Tracking

We’ve probably already listed all the wireless technologies. As you can see, they can all be used to track our location. But there is another technology that is not really associated much with connectivity. However, it is very effective and, worse, it is very difficult to tell if and possibly when our phone is using it. Ultrasonic Cross-Device Tracking, or uXDT for short, is a technology that can work on almost any device. It can be either a smartphone, tablet, laptop and basically anything equipped with a speaker and microphone. The basis of the technology’s operation is the ultrasound sent by the transmitter and received by our phone’s microphone. Suppose we are watching a commercial for some popular restaurant chain on TV and we have our smartphone with our phone with an app installed, also provided by that restaurant chain. Since our TV is equipped with speakers, it can additionally send out very high-frequency sounds not heard by humans during the advertisement broadcast. These sounds are captured by our phone’s microphone. If this restaurant chain’s application has access to a microphone, it can receive these sounds and interpret them accordingly. Depending on how this application is already programmed, it can further send data for analysis. Signals sent in this way can carry a gross of a dozen bits per second and over a distance of a few to several meters. It’s not too much, but it’s enough to transmit the ad identifier. The device with the application installed, i.e. our smartphone, can, upon receiving the identifier, perform such actions as sending our phone number, location or many other things to the advertiser’s designated servers. The location data can come from other technologies as well as be linked to the ad ID, for example, a given ad ID was only aired in a given location. What is even more attractive to the advertiser is that regardless of the manufacturer of our devices or their log-in data, they will be able to link all of our devices and create an even more accurate profile of our consumer habits based on the data we receive from them. Until now, if we used several different devices, the advertiser saw each of them as if it were a different person. On a smartphone, we were looking at pictures of cats, on a tablet at dresses and on a laptop at something work-related. With uXDT, the advertiser is able to link all of our devices to profile us even better. The ultrasound transmitter can be, also our laptop. If we watch an advertisement on it, or simply access some website that causes its speakers to emit ultrasound, profiling of us can also just take place. Virtually any device that can broadcast advertisements is capable of transmitting a uXDT signal. For this reason, owners of shopping malls, stadiums or other venues are interested in this technology to track their customers. Has it occurred to any of you to see that a smartphone app is using a microphone, even though it doesn’t seem to need it at all? This could be an indication that the app has such functionality. uXDT works on most speakers and most microphones available in stores. Not surprisingly, you can use this technology using almost any mobile device. It can be said that using this technology our phones do not overhear what we say, but they can easily listen to what other devices in close proximity have to say. The only way to block uXDT in apps on our smartphones is to disconnect or limit their access to the microphone. I encourage you to review your phone’s settings and pay close attention to whether certain apps have such access, even though they don’t seem to need it.


Information about our location is very valuable and quite easy to monetize. In fact, by simply carrying our favorite devices with us, we ourselves make it available to various entities, making us an even easier target for advertisers. There are really many technologies, and all used simultaneously, they are becoming extremely powerful and effective tools for profiling customers. This is what entire teams of statistics specialists are employed for. Big data is a big industry today, and it’s going to get bigger as the acquisition of consumer data becomes easier and easier over time. And whether we like it or not, wanting to experience a moment alone, let’s leave all modern devices at home, because nothing is a better spy than our own smart-gadgets.