A new lawsuit accusing Google of tracking people's locations against their will has served as a reminder that every movement of most smartphone users is being recorded, often without their knowledge.
The California man who filed the suit claims that the tech behemoth continued to track the whereabouts of Android smartphone users even after they turned off "location history".
But the history of geolocation and the privacy issues it raises are as old as the mobile phone itself.
- Early days -
Before smartphones arrived more than a decade ago, it was still possible to use geolocation. Mobile phones constantly connect to local antenna towers, and by triangulating the signals the user can be found -- as Jeff Goldblum illustrated in the 1996 movie "Independence Day".
However smartphones brought about a far simpler way to track people: GPS.
- GPS revolution -
After the release of the first iPhone revolutionised the industry in 2007, GPS -- Global Positioning System using satellites -- became prevalent, and it is now included on all smartphones.
Most apps now use location tracking, and not just for obvious purposes like maps and transport. It's also used for dating, food delivery and gaming, such as Pokemon Go, which became hugely if briefly popular across the world in 2016.
- Trackers on 75% of apps -
As the popularity of apps using geolocations grows, so does their money-making potential.
For example, when tourists use their phone to explore, they can be targeted with advertising not just from the country they are in but also the city and even the street they are standing on.
A 2014 study by CNIL, the French government's techonology consumer protection body, showed that between a quarter to a third of apps had access to the phone's location.
By 2017, a study by Yale University found that three quarters of Android apps contained trackers -- usually containing advertising.
The CNIL study also found that some apps tracked the phone's location more than a million times over a three-month period -- accessing the information about once per minute.
- Even flashlight apps -
The new Google lawsuit is far from the first time privacy concerns have been raised over geolocation. In 2011 fellow tech giant Apple faced a lawsuit over location tracking on its ubiquitous iPhones and iPads.
And there are also national security concerns.
In July of this year, researchers found that the fitness app Polar had revealed sensitive data on military and intelligence personnel from 69 countries. The app later disabled the function.
Just months before another health app, Strava, was found to have showed potentially sensitive information about US and allied forces around the world.
But the problem includes apps that don't even need to track the users' location.
Some simple flashlight apps have been discovered to have been secretly sharing location information.