Wednesday - Jun 19, 2019

How Does GPS Work?


GPS is easily one of the most revolutionary technologies of our time, but also one of the least understood technologies. Never mind that we depend on GPS daily to get directions to unfamiliar places, monitor weather patterns, execute rescue operations, follow stock market trades and even direct the operations of our military.

Most of us understand what it is and what it does, but how it works is another thing all together. Perhaps the little or lack of understanding can be attributed to the fact that the technology is free to anyone who wants to use it, thus eliminating the usual profit driven push that is synonymous with other popular technologies.

Here  is a look at what GPS is all about, what it does, and how it works.

What makes up GPS?

GPS deviceGPS is an acronym for Global Positioning System. It is essentially a system of satellites that was invented by the US government as an easy way of providing positioning, navigation and timing services.

The GPS satellites are owned and operated by the government of the United States. They were initially made for military navigation though now anyone with functional relevant technology is able to access the satellites' signals at no cost. 

When map based GPS navigation arrived around 2001, users found it hard to believe that the system was 100% free with neither contracts nor service plans. Most were sure there would be a catch somewhere down the line, but there was none. It was all free, remains free today and is predicted to forever remain free.

Navstar, the network

The GPS network that we use is known as Navstar,   This is the only system that is fully operational, though we have GLONASS by Russia, COMPASS  by China and GALILEO  by EU, all at varying stages of progress and or testing. Navstar was initially reserved for use by the US military before civilians were granted access starting 1983.

For the system to be functional at any one time, it must always contain a minimum of twenty four  radio satellites. The satellites fly over 12,000 miles above the surface of planet earth and orbit it twice daily.

Every single satellite is equipped with several atomic clocks, designed to keep accurate time.  They also contain wing-shaped solar panels that act as the poser source.

The working
At least four GPS satellites are 'visible' from the planet at any one time. Each of these satellites transmits information regarding its position and time. This information is transmitted at regular intervals via signals that travel at the speed of light. The signals are then intercepted by your GPS receiver device which calculates how far away the satellite is, depending on the time it took the message/signal to arrive at your device.  Once your device calculates how far away at least three satellites are, it can pinpoint your current location through a process known as trilateration.

To understand trilateration, imagine for a moment that you are standing somewhere on the Earth with three satellites in the sky right above you. If you can tell how far away you are from satellite 1, then you will know that you must be positioned somewhere on the red circle. Now, if you do the same for satellites 2 and 3, you can easily work out your current location by identifying where the three circles intersect. This is the same thing your GPS receiver does, but it makes use of overlapping spheres instead of the circles that we have used to demonstrate.

The more satellites available above the horizon,  the more the accuracy of your GPS device.

While the GPS satellites have on-board clocks that help to keep accurate time, differences will always occur between these clocks and an identical clock on the earth, due to factors to do with relativity. 

Why the GPS receiver is critical

The GPS system cannot work if the GPS receiver that is inbuilt in devices such as mobile  phones is not on. Once it is on, the unit automatically searches for the closest satellites and control station in that specific location. The higher the number of satellites a device is able to connect to, the higher the accuracy of the location and time information. Using the microwave-format of information, the device will be able to point accurately to the location and time that the satellites move through.

Information transfer from space to receiver

The satellites are positioned in a way that any GPS-enabled device can connect to at least four of them at a time. The satellites are constantly maintained to avoid a blank information window. As they orbit the earth, they are sending time and location signals that a cell phone is able to pick from the nearest control centers. Once your smart phone GPS receiver picks these signals, it is able to convert them into clear information on how far the satellite is form your current location.

Once the device receives these data form at least 4 satellites, it calculates your location geometrically. Three satellites are enough to locate you but the fourth one is to help in calculating your latitude.

There is a common misconception that the satellites can know about you! This is a big lie since your cell phone does not send any data to the satellite and neither does the satellite record any of your data.

GPS chain
A GPS chain is more or less the big picture of the distinct components that make up the GPS system. These can be broken down into three major parts:

The space compartment- this is the part that has a collection of satellites orbiting the earth (minimum of 24 satellites). The satellites gather and code location & time information. This information is then sent in microwaves towards the earth.

The control compartment- once the time and location microwaves are sent to earth, they have to be received and decoded to human-friendly format. The control unit is based on earth where it receives and decodes the waves.

The user compartment- this is the last part in the GPS chain. These are groups of users like the military and individuals who need the GPS information. As long as they have GPS receivers, they will access the information at all times and at no cost.

The future

GPS on mobileGPS is fast becoming a daily tool for millions of people worldwide. GPS devices are now available in watches, mobile phones and even cloths. To ensure that the satellites are abreast with today’s technology, the American government has paved way for the next generation of satellites dubbed GPS III. These new satellites will increase the accuracy of information and are expected to last longer than the current generation.


All trends point to an exciting future for businesses and individuals who happily use GPS in their daily activities. Millions more will utilize the system as it grows both in quality and sophistication.