How Does GPS Works

What Is GPS?

The Global Positioning System or GPS is a great navigational tool that can be used by anyone, anywhere in the world. It is made up of 24 satellites and provides accurate navigation data 24/7. Best of all, there are no subscription fees or setup charges.

The first GPS satellite was launched in 1978 as a project for the U.S. military. By 1994, there were 24 GPS satellites orbiting Earth. GPS was not very accurate when it first became available for civilian use. It would only locate a GPS receiver within about 300 meters (1,000 feet). Today, a much more accurate signal is free and available to anyone with a GPS receiver.

The GPS system that we use in America is not the only one. Russia has its own version called GLONASS (Global Orbiting Navigation Satellite System). China and the European Union are also currently in development of similar systems.

How GPS Works

The Global Positioning System (GPS) uses 24 satellites that orbit the Earth twice a day in a circular path and about 12,000 miles above us. They travel at speeds of roughly 7,000 miles per hour. Small rocket boosters keep each satellite on its intended track. Each satellite broadcasts a distinct signal and orbital parameters to allow GPS receivers to decode and compute the precise position of the satellite.

Data are collected and used by GPS receivers to calculate a person’s precise position. In simple terms, the GPS receiver measures the time it takes for a signal to arrive after calculating distance from each satellite using timing data from several more satellites.

The receiver will compute a user’s position and display it on an electronic map. Allowing for you to get directions to basically anywhere.

GPS satellites house atomic clocks that provide unrivaled accuracy for time. This information is broadcasted by the satellite so that a receiver can determine when the signal was initially sent. The signal also contains other data that helps receivers compute the locations of additional satellites and to make any adjustments necessary for pinpointing positioning.

The receiver computes the distance, or range, from the receiver to the satellite by subtracting the time difference between signal reception and broadcast time. The ionosphere and troposphere must be incorporated into the calculation.

The receiver can use this information to compute its own three-dimensional position after calculating ranges from three signals. Also with the help of information about the ranges to three satellites and the satellite location when the signal was sent. In order to calculate range estimates from these three transmissions, an atomic clock synchronized to GPS is required.

The addition of a fourth satellite allows the receiver to calculate latitude, longitude, altitude, and time without needing an atomic clock.

GPS requires a connection with at least three satellites to triangulate your 2D position (latitude and longitude) as well as monitor movement. You can find GPS in many devices such as smartwatches, satellite communicators, automobiles, boats and more.

A GPS receiver needs four satellites in view to calculate your three-dimensional position (latitude, longitude, and altitude). The device usually tracks eight or more satellites, but that number can differ based on the time of day and location.

GPS units doesn’t only tell you your location. Once it has pinpointed where you are, it can also give information about:

  • How fast you are moving (speed)
  • The direction you’re facing (bearing)
  • The route you’re taking (track)
  • How far along your journey you are (trip distance)
  • How much further until your destination (distance to destination)
  • When the sun will rise and set

How Accurate Are GPS Systems?

It varies. GPS satellites broadcast their signals with great accuracy, but what you receive is influenced by numerous elements such as satellite geometry, signal obstruction, atmospheric conditions, and receiver design features/quality.

The basic GPS service has an accuracy of approximately 7 meters 95 percent of the time, anywhere on or near the earth’s surface. Each of the 31 satellites sends signals to receivers, which use a mix of signals from at least four satellites to fix their position and time.

GPS-enabled mobile phones are often within a 4.9 m (16 ft.) radius under open sky, but their accuracy decreases as you approach structures, bridges, and trees.

By using dual-frequency receivers and/or augmentation systems, GPS accuracy improves significantly for high-end users, allowing real-time positioning within a few centimeters. Long term measurements are also improved at the millimeter level.

What Signals Does GPS Use?

L1 (1575.42 MHz) and L2 (1227.60MHz) are the two frequencies used by GPS satellites to communicate data. The atomic clocks aboard the satellite generate the fundamental L-band frequency, 10.23 Mhz. The carrier frequencies are generated by multiplying the common 10.23Mhz by 154 for L1 and 120 for L2.

At least two low-power radio signals are transmitted by GPS satellites. The way signals travel is mainly limited to line of sight, meaning they can go through clouds, glass, and plastic but not most solid objects like buildings and mountains. However, modern receivers are more sensitive and as a result can usually track even when there is a house in between them and the satellite.

A GPS signal is comprised of three types of data:

  • Pseudorandom Code – I.D. codes that identify which satellite is sending data. On your device’s satellite screen, you can look at which satellites you’re receiving transmissions from.
  • Ephemeris Data – Critical to understanding a satellite’s position and provides key insights into the current date, time, and health of the satellite.
  • Almanac data – Instructs the GPS receiver on where each GPS satellite should be at any given moment during the day and supplies orbital information for that satellite and every other satellite in the system.

What Effects GPS Signals?

The following factors can affect GPS signal, accuracy and be responsible for showing you in the wrong place:

  • Ionosphere and troposphere miscalculations: The satellite signals slow down as they pass through the atmosphere, which is why the GPS system uses a built-in model to fix this issue.
  • Reflecting signal: The GPS signal may be reflected off of tall buildings or large rock surfaces before it reaches the receiver, increasing signal travel time and causing errors.
  • GPS receiver clock miscalculations: Because a receiver’s internal clock is less precise than the atomic clocks on GPS satellites, it may have slight timing errors.
  • Visible satellites: The more satellites a GPS receiver can “see,” the more accurate it is. You may get position errors or perhaps no position reading at all if a signal is blocked. GPS units are not capable of operating underwater or underground, but new high-sensitivity receivers are able to pick up on some signals when inside buildings or beneath tree cover.
  • Satellite orbit errors: The satellite’s reported position may be incorrect.
  • Satellite geometry: The farther apart the satellites are when viewed from Earth, the stronger their signals, which is why broadcast networks prefer to put all of their transmitters in one spot rather than at wide angles.
  • Poor signal: Being indoors or underground.

Why Does GPS Give Me Wrong Directions Sometimes?

New roads, closed roads, lane changes, and other adjustments are all expected every year. Consider any new construction in your neighborhood – it may take months or years for the road to open once it’s finished.

Those new routes will eventually appear in the next iteration of digital mapping software, but it’s not a snap of the fingers. To construct maps that represent the real road systems across the world, the largest mapping and navigation businesses utilize on-the-ground technology (employees driving around and collecting data), user feedback, and a variety of other sources.

The Navigations Systems Research Foundation conducted a study and found that GPS systems may overlook crucial details, such as the type of road. Knowing this information is essential if your bus gets routed through a residential area or your car ends up on an unpaved road.

Although outdated map data is often due to inaccuracies in the map itself, user error is usually to blame. By connecting your handheld or stand-alone GPS device directly to a computer, you can frequently download updated maps from your digital map provider for free. In this way, your GPS will always have the most current routing information available.

Even with the most up-to-date mapping and navigation technology, your GPS device is still reliant on the coverage of its satellite network. Atmospheric disturbances, as well as terrestrial influences, can all cause errors.

If a satellite isn’t able to communicate its location, it won’t be able to link up with your GPS receiver. In the ionosphere and troposphere, atmospheric factors like as plasma activity, temperature, pressure, and humidity might cause calculation and accuracy problems in the satellite network.

The two most common GPS issues are weak signals and signal interference. If there’s something between your device and the satellite network, it causes a problem with the signal. This could be anything from tall buildings to trees to mountains. A clear uninterrupted signal will also be your best bet for getting the most accurate signal.

Conclusion

GPS systems are becoming increasingly commonplace, being used daily by most people. Sometimes weather they or not. But the technology not perfect as it requires so much precision and alignment of many factors.

New roads, construction, and other changes can quickly make a GPS system outdated. Additionally, atmospheric conditions and signal interference can cause inaccurate readings. However, by keeping your maps up to date and ensuring that your GPS device has a clear signal, you can minimize the chances of getting inaccurate directions and getting lost in the process.

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