## How Does GPS Work?

In this article we will give you Full info About How Does GPS Work? or How GPS works? Satellite navigation relies on a global network of satellites in medium-earth orbit transmitting radio signals. The 31 Global Positioning System (GPS) satellites are most familiar to satellite navigation users.

The United States, which invented and operates GPS, and Russia, which invented and operates GLONASS, have both given free use of their systems to the rest of the world. GPS and GLONASS have been adopted as the core for an international civil satellite navigation capability known as the Global Navigation Satellite System (GNSS) by the International Civil Aviation Organization (ICAO) and other international user groups (GNSS).

## GPS Satellites

The basic GPS service gives customers an accuracy of about 7.8 meters 95 percent of the time, anywhere on or near the earth’s surface. To do so, each of the 31 satellites sends signals to receivers, which uses the difference between the time a signal is sent and the time it is received to calculate their location. The atomic clocks carried by GPS satellites provide exceptionally accurate time.

The time information is included in the satellite’s broadcast codes so that a receiver can keep track of when the signal was broadcast. The signal comprises information that a receiver needs to calculate satellite positions and make other changes necessary for precise positioning.

The distance or range, between the receiver and the satellite, is calculated using the time difference between signal reception and broadcast time. The receiver must account for ionosphere and troposphere propagation delays, as well as signal speed reductions. The receiver may compute its own three-dimensional position using information about the ranges to three satellites and the location of the satellite when the signal was sent. To determine ranges from these three signals, an anatomic clock synchronized to GPS is necessary.

The receiver, on the other hand, eliminates the necessity for an atomic clock by taking a measurement from a fourth satellite. As a result, the receiver computes latitude, longitude, altitude, and time using four satellites.

GPS has already been ingrained in our daily lives, and these examples demonstrate a few beneficial applications. (insert upbeat music) GPS is a fascinating technology. It employs a 24-satellite system that orbits the Earth continually, with at least four satellites required to track your location. It runs on an atomic clock, and the time error on your phone is also a major worry.

Furthermore, GPS technology relies heavily on **Albert Einstein**‘s theory of relativity. Finally, a practical application of relativity theory. Let’s set aside all of the complexities and learn about GPS technology in a rational and step-by-step approach. Assume that your friend wants to know where you are and that you have a smartphone with a built-in GPS receiver. Trilateration is an interesting mathematical approach used in GPS to locate someone’s position.

## Trilateration

Let’s start with a two-dimensional understanding of trilateration. In two-dimensional trilateration, at least two satellites are necessary to determine your position. The satellites use technical techniques to calculate the distance between you and the satellites. The methods for doing so will be discussed later. Things are now simple. You are at a distance of R1 according to the first satellite.

As a result, you should be on this circle someplace. You should be on this circle because the second satellite knows you’re at a distance of R2. As a result, your current position must satisfy both of these criteria. In a nutshell, you should be at the crossroads. Now there’s a minor snag. There are two points where the paths cross. So,

## What’s your final stance?

The third circle represents the Earth’s surface, and the implausible solution is eliminated. The same approach can be used in the three-dimensional universe.

We’ll need three satellites instead of two in this case. The satellite recognizes you as being anywhere on a sphere in the three-dimensional universe. The usage of a second satellite reduces your position to a circle. It’s worth noting that the intersection of two spheres results in a circle. You may now narrow down your location to just two points with the help of a third satellite. The intersection of a circle and a sphere yields two points in this case. Using the Earth as the fourth surface, we obtain the proper location, the three spatial coordinates, just as we did in the prior situation. Let’s have a look at how the distance between you and the satellite is calculated.

## ATOMIC CLOCK

All of the satellites have an extremely precise atomic clock. The satellite transmits a radio signal to Earth on a regular basis. The exact moment the signal was transmitted, as well as the satellite’s position, will be included in this radio transmission. Assume the recipient has a highly accurate clock as well. The signal is received by a receiver on Earth. This image depicts a standard smartphone GPS receiver. Your receiver receives the signal after a specific amount of time since radio waves move at the speed of light.

You can calculate the distance between you and the satellites by taking the difference between the sent and received times and multiplying it by the speed of light. Because the satellite has already told you its coordinates, you may easily construct a sphere around the satellite’s centre point to determine your location, as previously taught.

## INACCURACY

One thing to keep in mind is that the time measurement must be quite precise. Because the speed of light is so great, even a microsecond error will result in a kilometers-long error. Now we get to the meat of the matter. The time on your radio isn’t very accurate. Your cell phones and laptops use crystal clocks, which are not as accurate as atomic clocks.

It is absolutely impractical to include an atomic clock in a smartphone. By checking the time settings on your smartphone, you can quickly see how accurate it is compared to an atomic clock. The discrepancy between actual time and the time recorded by your phone is referred to as time offset. This time difference will result in a significant inaccuracy in GPS computations.

## How do we overcome this issue?

The good news is that your smartphone’s time offset is the same as all three satellites because they all keep the same time. Your device’s time offset value becomes the new unknown. This means that in addition to the three spatial coordinates, we must also compute your receiver’s time offset value. To solve this fourth unknown, we require an extra satellite measurement, which is why we need four satellites to measure your location. This eliminates the need for an atomic clock in your smartphone.

If you look at your current GPS constellation, you’ll notice that at any given time, at least four satellites can see your location. Please stay with us, this Article isn’t ended yet; we’ve got one more problem to solve. Even with all of these powerful technologies, this GPS system will not locate you correctly. This is where **Einstein’s theory of relativity** comes into play.

Time is not absolute; it is influenced by a variety of things. A fast-moving clock will slow down, according to special relativity theory. Every day, the atomic clocks, which travel at 14,000 kilometers per hour, will slow down by seven microseconds. Because the satellites are 20,000 kilometers above the Earth and experience one-quarter of the Earth’s gravity, the clocks will tick somewhat quicker, according to Einstein’s general relativity theory. Every day, roughly 45 microseconds in this example. This indicates that the atomic clock creates a net 38 microseconds offset per day.

A theory of relativity equation is embedded into the computer chips to compensate for this, and it modifies the rates of the atomic clocks. The GPS would have caused a daily inaccuracy of 10 kilometers without this application of relativity theory. The GPS system was developed by the US Department of Defense and is available to the general public for free.

However, in many countries now, accurate alternatives are accessible. To determine the most accurate position, modern receivers use GPS and other navigation systems at the same time. Now, let me ask you a brief question.

## Does GPG require an internet connection?

There is no need for an internet connection or a cell phone signal to use GPS. However, with their assistance, GPS setup can be significantly accelerated. Instead of slow direct satellite downloads, satellite location information can be downloaded via the internet. Assistive GPS systems are the name for these types of GPS systems. So, the next time you track your food delivery or drive your automobile, remember how significant Einstein’s theory of relativity and other mathematical theories are in the development of GPS.