Global positioning satellites beam signals to special receivers on Earth. These receivers, which are not much larger than mobile phones, know the difference between when the satellite signal was sent and when it was received. This allows the receiver to work out the distance between each of the satellites and itself, and there-fore calculate its position.
GPS is accurate and handy to use, so much so that we rely on it more and more every day. It’s not often we take the time to learn how it works. The idea of GPS refers to a Global Positioning System; a collection of satellites in orbit above the Earth that transmit location data down to our devices. As hobbyists, we can get GPS modules that will read and interpret this data for us! They’re known as GPS receivers, and they are used everywhere, like your phone, tablet, and other electronic devices. GPS receivers will relay a satellite’s location data directly to a microcontroller in the form of serial data strings, which we can break down into relevant bite-sized chunks of data about where we are and how we are moving!
Firstly, the signal of time is sent from a GPS satellite at a given point. Subsequently, the time difference between GPS time and the point of time clock which GPS receiver receives the time signal will be calculated to generate the distance from the receiver to the satellite. The same process will be done with three other available satellites. It is possible to calculate the position of the GPS receiver from distance from the GPS receiver to three satellites. However, the position generated by means of this method is not accurate, for there is an error in calculated distance between satellites and a GPS receiver, which arises from a time error on the clock incorporated into a GPS receiver. For a satellite, an atomic clock is incorporated to generate on-the-spot time information, but the time generated by clocks incorporated into GPS receivers is not as precise as the time generated by atomic clocks on satellites. Here, the fourth satellite comes to play its role: the distance from the fourth satellite to the receiver can be used to compute the position in relations to the position data generated by distance between three satellites and the receiver, hence reducing the margin of error in position accuracy.
The Fig 1-3 below illustrates an example of positioning by two dimensions (position acquisition by using two given points). We can compute where we are at by calculating distance from two given points, and the GPS is the system that can be illustrated by multiplying given points and replacing them with GPS satellites on this figure.