Science Behind Sat Navs

How do sat navs work?

Research has found that 52% of car drivers now have and use a sat nav device in their vehicle. Many now come installed in new cars and vans and are an essential tool for a lot of road users to ensure they do not get lost on long or short journeys.

Sat nav science

Whether you use a sat nav with an external piece of equipment or through your phone, they all tend to do the same thing and work in similar ways.

GPS Satellites

Sat navs use the Global Positioning System (GPS) to determine the exact position of where you are on earth. GPS is a system which uses a network of 30 satellites that were originally sent into space for military purposes.


Wherever in the world you are, at least four GPS satellites will be visible, but only three are required to generate an accurate location. Sat navs use the information sent from three separate satellites to calculate the sat nav’s exact destination, this is trilateration.

Sat navs use GPS for navigation

When the vehicle moves the three satellites will recalculate the location and if it moves outside of one sphere then the sphere of another satellite should pick it up. When all this is in place and there is a decent signal, further information can be calculated, such as speed, distance to destination, trip distance and more.

If for some reason the sat nav cannot lock onto three satellites, then a position will not be generated. To get a 3D position you need to use four satellites rather than the standard three.

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When sat navs go wrong

We all love a good tragic story and some of these are the best ones we’ve heard. If only they would have applied some form of logic whilst driving.

Not suitable for off land

A man had to be rescued after using a sat nav on a boat down the River Thames. The man was trying to reach Kent and thought it would be a good idea to follow the device dedicated to roads.

A woman ruined a very expensive Mercedes after driving straight into a river and being washed a couple of hundred metres down river.

Similar names

When sat navs go wrong

Our favourite story is of the truck driver who was trying to get to Gibraltar (near Spain) but ended up at Gibraltar Point in Lincolnshire. Fair play to him though, he was only 1,600 miles wrong. Easy mistake.

A group of Christmas shoppers managed to drive to the wrong country and ended up in Belgium instead of France after inputting “Lille” into their sat nav.

School kids were disappointed when they were taken to a random side street in London rather than Henry VII’s old palace. Even the school teacher hadn’t realised the mistake and thought it must have been round the corner (it’s at least 1.5 hours away!)

It could be argued that as a society we are now over reliant on technology, but given that the benefits of Sat navs appear outweigh the negatives, their use is only likely to increase.

GPS Accuracy

GPS has developed a lot since the 1980s to become ever more accurate. Receivers WAAS capability are the most accurate and are the ones you find on aeroplanes as they have the ability to keep GPS through the entirety of any flight.

Sat navs in Society

The use of Sat navs is now so prevalent that it is being incorporated into the ‘independent driving’ sector of the UK’s driving test, with candidates having to follow directions from a Sat nav accurately to pass.

There is also a multi-million pound project underway to create a database with information about 200,000 miles of roadways. This is to provide accurate road widths, weight restrictions and bridge heights to prevent lorries and cars getting stuck.  

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