The thought of travelling to a far-off village with a road map in tow has become antiquated in recent years, and that’s primarily due to satellite navigation. This remarkable tech is now so common that most of us carry a global navigation system in our pockets every day.
Sat nav was originally invented for the US military, and was based on primitive navigation systems that had been prototyped in the 1960s. Mapping as we know it was opened up to consumers after the US government decrypted its navigation systems and improved accuracy, which took place around 20 years ago.
In the mid-2000s, the first commercially available sat nav systems were fitted to cars, and there’s now very little practical difference between the system on your phone and the system used by the military.
How Sat Nav Works - the Basics
The GPS chip in your phone or sat nav system scans the sky looking for positioning satellites. There are 24 of these satellites currently in orbit, although your sat nav only needs to be able to see three of them to get a location. In practice, most of our devices can see several at any time.
If your device can see four satellites, rather than three, it gets a little bit more information: it can also calculate your altitude.
The phone in your pocket, or sat nav in your car, still requires the resources of the US military on the ground, too. Two ground stations in the United States ensure that the satellites are functional by tracking data from a global network of monitoring stations. There’s more information on the US government website.
Calculating location in this way is fraught with complicated problems. For example, although these satellites carry atomic clocks, the time stamps they generate can be slowed down by the earth’s atmosphere. Also, time ticks by at a slightly different speed in space, because the pull of gravity is different. So sat nav satellites have to be able to compensate for all of these small differences to give an accurate location.
Sat nav has evolved in the last few years, fuelled in part by the rise in 4G connectivity. Now, maps can be automatically updated when roads are closed, or when roadworks are in place, giving people more useful directions. Additionally, 4G is used in combination with self-driving technology to create driverless vehicle systems.
In theory, this will mean that self-driving cars will soon be able to avoid collision by constantly knowing the location of all the other cars around them.
This combination of GPS and two-way connectivity has also turned sat nav into a way to track and locate people. There’s still controversy over the use of location data by companies that track us to sell us things and serve us ads.
The one downside of all this clever tech is that it could be switched off or disrupted, and there are signs that sat nav signals are already being jammed by rogue states as a form of cyber attack. In fact, the humble sat nav is perhaps one of the most important advances of the modern world because most of us are so dependent on it being functional.
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