What is GPS and Other Satellite Navigation Systems

The truth is that in the age in which we live, the term GPS is undoubtedly widely used. Its use in smartphones has made many people know this geolocation system in one of its many utilities. However, the vast majority of people do not know what exactly a GPS is , how it basically works and the different positioning systems that exist. If you want to know a little more about it, we will show you below.

The daily use of GPS to know how to get to an address with the car or walking from our mobile phone, locate a specific point on a map or share our location with friends through WhatsApp, has made it familiar to us. However, few have stopped to think about how it is possible to know the exact location of a person, car or object in this simple way and how the global positioning system works.

GPS

What is GPS and how does it work?

GPS stands for Global Positioning System or in English, Global Positioning System . Basically, it is a satellite-based navigation system ( GNSS ) and was developed by the United States Department of Defense in the early 1970s. A system that allows us to know the location of any person, vehicle or thing , the speed at which it moves and other data such as its height at any time and point on the globe.

GPS works through a network of at least 24 satellites that are in orbit over our planet, approximately 20,000 km high, with orbits distributed so that at least four satellites are visible at any point on Earth at any time.

GPS

That is, when we want to determine the exact position of someone or something, the receiver we use must locate at least four of these network satellites, from which it will receive signals indicating the identification and time of each one of them and the information about the constellation. Based on these signals, the receiver synchronizes its own clock with the time of the GPS system and calculates the time it takes for the signals to reach the equipment to calculate the distance with the satellite. Next, taking into account the speed of the signal and using the reverse trilateration method, it calculates its own position . We could say that satellite positioning works basically in this way, but the truth is that very complex algorithms are used in these calculations.

We could therefore say that the GPS is made up of three elements, the user , the control and the space . The space is the one that refers to the constellation of satellites in Earth’s orbit, distributed in different orbital planes. The control station is made up of tracking stations across the globe and a main station, which are responsible for tracking satellites, updating their positions, and synchronizing their clocks. And finally, the component element of the user, which is nothing other than that used by a GPS receiver to receive and understand all the GPS signals received and transform them according to the application used so that the user can obtain the information they expect and in the manner adequate. In this last element, it is where the antennas and the processing software of the device used as a receiver also come into play.

GPS applications and uses

Although the origin of satellite navigation was military, the truth is that over time its applications and uses have been very different. At first its use was professional, however, for more than 20 years, the GPS system has been used in numerous activities and devices in our daily lives.

  • Military use : GPS was born as a tool for military use with the idea of developing a system that was capable of providing the exact location or speed of an object or person and which was later used for other purposes such as the development of radio navigation systems. or launching weapons at a certain geographical location, among others.
  • Land, sea and air navigation : Some of these tools also ended up being used by civilians and the military in all kinds of means, such as land, sea and air navigation.
  • Locating people, animals and things : Without a doubt, it is a great utility in locating people, animals, vehicles or other types of objects for very different purposes, rescue activities, research, etc.
  • Public and private security: In this area, GPS also has multiple applications as a personal security tool, anti-theft measures or its integration into alarms, etc.
  • Cartography and engineering : Needless to say, it is also used to obtain precise and reliable data from any point on the globe, detection of localized seismic movements with great accuracy, as well as to carry out measurements or real-time monitoring of large deformations structures due to overloads, etc.
  • Devices and mobile phones : It is one of the systems that is not lacking in today’s mobile phones and in which we can use GPS for different purposes. Among the main ones, it is worth noting the possibility of locating the device in case of theft or loss, GPS navigation when we go in the car, bike, motorcycle or on foot, use of applications that require this functionality or even games.
  • Sport : Another of the most widespread uses today is in devices for sports. They allow to know and control the progression of our training and performance with great precision. Thanks to the GPS it is possible to know the rhythm of the race that we carry, the distance covered the unevenness of our route, etc.

Other satellite navigation systems

There is no doubt that GPS is the best known and most popular Global Navigation Satellite System (GNSS), however there are other satellite navigation systems such as GLONASS, GALILEO or BEIDOU.

GALILEO

Galileo is the European radio navigation and satellite positioning system developed by the European Union in collaboration with the European Space Agency, providing the EU with an independent technology of the American GPS. A system of creation, management and civil use that was launched in December 2016.

It has about 30 medium-orbit satellites located about 23,000 kilometers high, connected to a series of ground sensors and control centers located in different areas of our planet. Three of them come from the Spanish Space Agency and six of them are spare.

GPS

The main characteristic of Galileo is that it is a civil satellite navigation system. Therefore, the services it offers in real time can be used by any user who has a compatible device. Its dual frequency offers greater precision in real-time positioning, also improving the performance of the system in adverse weather situations. Meanwhile, the search and rescue service works through SAR beacons, similar to those used by ships and planes.

Recently, the news was echoed that Galileo was acquiring new functions that other networks do not have, such as the possibility of sending and receiving SOS signals . In other words, it allows receiving, transmitting and locating distress signals and, in addition, responding to these signals by sending confirmation that the location and the distress request have been received correctly.

Although the truth is that we are not yet aware, there are many smartphones that we can find today on the market that incorporate the Galileo system. Many mobiles and receivers in the agriculture sector are already capable of working with the European satellite navigation system.

GLONASS

GLONASS is the global satellite navigation system created by Russia for geographic location on the Earth’s surface. Another alternative to the United States-created GPS system that uses or consists of a constellation of 31 satellites, 24 active, 3 spare satellites, 2 in maintenance, one in service, and one in testing. Satellites located in three orbital planes at an altitude of 19,100 kilometers above Earth.

Although the satellites began to be put into orbit in 1982, they did not begin to be functional until 1996, consequently the coverage of the entire territory of the former Soviet Union as of 2007. To this day, they cover the entire world, their utilization is freely available and Russia continues to work on updating its satellite constellation.

GPS

As far as operation is concerned, GLONASS requires the use of at least three satellites of the constellation to be able to triangulate signals and know exactly the position of a person or thing with great accuracy. Each satellite indicates that the receiver is at a point on the Earth’s surface, centering on the satellite itself and radio the total distance to the receiver.

By obtaining information from at least two more satellites, a circumference is determined that results from the intersection of the spheres at some point where the receiver is located. Now, if we also need to know the altitude of that point, then it will require one more satellite. Therefore, the use of at least four satellites is required for three-dimensional navigation with GLONASS.

BEIDOU

This time, it is the Chinese satellite navigation system. It is made up of two separate satellite constellations and began operating in the Asian country in late 2011 with a partial constellation of 10 satellites in orbit. Later, more satellites were launched to the point of reaching 35.

BEIDOU is therefore an alternative global satellite navigation system to the Global Positioning System (GPS) of the United States, the Russian GLONASS and the European Galileo. The operation of the Chinese system depends in the first instance on the central control station, which is the one that sends consultation signals to users through two active satellites and the one that returns a response when the receivers receive these signals.

The central or master control station receives the response signals sent by the receivers from the satellites and calculates the user’s 2D position based on the time difference between the two signals , which is also compared with a digital territorial map stored in the system database to obtain the three-dimensional position.