What is GPS and How Does it Work?

What do you do if you have to travel in an uncharted territory? Well, gone are the days of complex maps and asking for directions. You simply use your GPS to reach your destination. But not many of us know how GPS originated, what is GPS, how GPS works, types of GPS or even the full form of GPS.

What is GPS?

To put it simply, the GPS (or Global Positioning System) is a navigation system based on use of satellites. It offers location and time services to civilian and military users for navigation of ships, commercial trucks and even passenger vehicles.

How is GPS Different From GIS?

GPS term full form is Global Positioning System. It is not to be confused with GIS, whose full form is Geographical Information System. They ought not to be confused with each other though they are closely related.

While GPS is a navigation system that military and civilian users rely upon, GIS is a software program. It is used to utilize the information generated by the information collected from GPS satellites. The main purpose of GIS is not to enable smooth navigation but to use the data created by GPS satellites for mapping and geospatial analysis. However, GIS is not limited to exploiting the data generated by GPS. It is also used for weather forecast, exploitation of natural resources, management of land information, and using the geospatial analysis for better decision-making.  It also relies upon data generated from other sources like aerial photographs and information provided by other communications satellites.

GPS based on satellites

The navigation system uses a set of satellites that rotate around the earth every 12 hours and map worldwide time, position & velocity information. The satellites help in identifying different locations on the globe and mapping the distance between them. The system keeps performing for 365 days a year, irrespective of the changing weather and environment. For the final user, GPS is a means of finding exact locations on an electronic application and navigating towards it. Initially, GPS was meant for military application but in 1980, it was also extended to civilian use.

How GPS works?

It works through a technique called trilateration. This technique relies on signals transmitted by the satellites to calculate physical dimensions like location, velocity and elevation. Satellites orbiting the earth transmit signals that are picked up and analyzed by the GPS devices located on or near the earth’s surface. It is not possible to track a location from a single satellite, as the microwave signal picked up by a GPS device only relates to the distance between the device and the satellite. There is no information about the angles that could be used to pinpoint the location of a GPS device.

This is why multiple satellites are used by the navigation system. When signals from three satellites are picked by a GPS device, its location can be finally determined as it will be located at the intersection of the radia created by the satellites. Since satellites produce a sphere rather than a circle, there will be two points of intersection and the device will be located on the point closest to the surface of the earth.

During navigation, real-time data is used to monitor velocity and movement. Since the distances from the satellites keep changing, the spheres also keep changing and so do the points of intersection. This enables the navigation system to constantly check the movement of the GPS device as well as the velocity with which the GPS device is moving.

Three elements of GPS

Like any other navigation system, the GPS too relies on three basic elements for its smooth functioning.

• Space segment

The accuracy of any navigation system depends on the number of satellites and their capabilities used. GPS uses a constellation of 31 satellites placed at a height of 20,000 km above our planet. Each satellite sends out microwave signals that are received and interpreted by receivers on GPS devices.

• Control segment

The control segment is the ground segment of the GPS navigation system. This is not very different from a remote tower. The control segment plays a critical role in managing the space-based segment, that is, the satellites and ensuring their proper functioning at all times.

• User segment

This is very we interact with the Global Positioning System. Our GPS devices, which may be a smartphone, a smartscreen on our cars, military hardware, aviation systems or maritime equipment, carry inbuilt receivers. These GPS receivers are a simple combination of an antenna and a processor.

The antenna is the hardware that picks up microwave signals being transmitted by the satellites. The processor attached to the electronic devices then starts the function of reading and interpreting the received information. It is the receiver that performs trilateration to locate the GPS device at a particular point on the planet. It further enables monitoring of movement and velocity of devices.

GPS is a sophisticated technology but it is already in a state of high advancement. The receivers form only a small part of your smartphones despite all their potential.

Types of GPS

The Global Positioning System (GPS) has grown in a rather organic way. Initially, it was restricted to military use. Later, it was opened up for civilian use and gradually it has become the preferred digital assistance for commutation. Therefore, it has evolved over several decades and different types of GPS have come up in the process. The fundamental principle remains the same, but different types of GPS are equipped to meet different kinds of needs. The types of GPS systems include:

1. A-GPS

Assisted GPS (A-GPS) allows receivers to gather information from local network sources and facilitate tracking location of the satellites. It is useful in conditions where satellite signals are obstructed by different obstacles like buildings and trees. It however works only on systems that have cellular networks

2. S-GPS

Simultaneous GPS (S-GPS) is used in case of emergency services like police patrols, ambulance and fire services. It is a unique function that allows both voice data and GPS signaling to be transmitted directly from a smartphone simultaneously. For emergency services, this allows the flexibility of tapping into GPS location services while also conversing on a telephone call with the victim.

3. D-GPS

Differential GPS (D-GPS) is an improvement upon the traditional GPS service in terms of accuracy and precision. The range of error in the traditional GPS service can be reduced to a minimum of 15 meters. However, correction technique used in D-GPS can further narrow down the range of error to just 1 inch (2.5 cm). It works using a network of fixed ground stations that rectify the difference between the satellite locations and known fixed locations.

4. Non-differential GPS

It is the exact opposite of D-GPS. It uses direct satellite signals for the purpose of tracking location and doesn’t rely on any rectification. So, there will be less accuracy but much greater and frequent use.

5. Mapping and non-mapping GPS

Mapping GPS is what you maybe most familiar with. It comes with in-built maps and also allows use to download maps and add them to your navigation system. This the type of GPS that you mostly use while driving an automobile or finding a store in the shopping mall. Most mobile devices, tablets and other handheld electronic devices now come equipped with a mapping GPS.

Non-mapping GPS, on the other hand, comes without any maps. This type of GPS displays your location. It also helps you in finding the direction to reach another point without having to take guidance of any human agency or without keeping a check on the pathways or landmarks.

Applications of GPS

GPS technology has several applications depending on the type of user and the field of use. Navigation and tracking location are the kind of services that different professionals would want to use. And now it has become popular in everyday use too. Following are some of the different uses of GPS-

1. Navigation of automobiles
2. Emergency services
3. Application in the aviation industry
4. Law enforcement services
5. Finance-related services
6. Finding lost devices and automobiles through GPS-enabled services
7. Health and fitness services
8. Use of agricultural equipment
9. Monitoring children
10. Use in military operations

Conclusion

GPS is incredibly popular amongst all kinds of users, whether civilian or military. The accuracy of GPS services though varies considerably according to the needs of a particular user.

GPS become quite affordable and such devices are the drivers of the IoT revolution. It makes our devices smarter and adds value to the electronics that we use on an everyday basis.