What Is GPS and How It Works: A Complete Guide

GPS is quickly becoming an everyday technology. The apps on our mobile phones utilize GPS to provide functionality that wouldn’t be possible otherwise. For example, think of a list of recommended restaurants near you. GPS makes that possible. In-car navigation is another modern convenience that wouldn’t exist without GPS.

The same technology is used in autonomous vehicles, package tracking, military applications, and much more. But have you ever wondered what a GPS is, exactly? If you’ve ever asked yourself that question or just pondered how GPS works, this guide will tell you everything you need to know.

What is GPS?

The Global Positioning System, or GPS, is a satellite-based positioning, navigation, and timing (PNT) system maintained by the United States Space Force. It provides precise location data via satellites orbiting the Earth. While GPS is a US military project and was initially designed for its use only, today, it’s available to everyone in the world to use however they like.

The GPS initiative began in 1973, with its first satellite launching in 1978. Nine more of the first GPS satellite series — Block I — launched between 1978 and 1981. The Block II series featured several technological upgrades and began launching in 1989. The more advanced Block III satellites were first launched in 2018.

While GPS was first conceived to provide navigation and timing information to the military, it has numerous other purposes today. GPS is now a staple in the fields of navigation, mapping, and surveying. It provides timekeeping for various applications worldwide, and the technology’s functionality and accuracy improve many scientific endeavors.

What Are the Three Main Elements of GPS?

GPS relies on three main components: a network of satellites, ground control stations, and receivers. Each element is as important as the others in providing the functionality you’ve come to expect from GPS.

Satellites: The Backbone of GPS

The beating heart of GPS is the network of Block I, II, and III satellites in constant orbit around the Earth. The satellites continuously transmit radio signals containing precise orbital and timing data.

Ground Control: Managing GPS Satellite Networks

GPS ground control stations monitor and control the satellites to help ensure accuracy and reliability. Ground stations track the satellites’ orbit patterns, adjust their clocks, and upload critical navigation data.

Receivers: Interpreting GPS Signals

GPS receivers are found in smartphones, car navigation systems, and specialized tracking devices. Regardless of their form, each GPS receiver collects and processes signals from the satellites. The receiver takes the GPS data and calculates their precise location. By measuring the time it takes for signals to reach the receiver from multiple GPS satellites, a receiver determines its longitude, latitude, and altitude position.

How GPS Works: The Technical Details

The three main elements of the GPS system work together to determine a receiver’s location with unparalleled accuracy. Here’s how it all comes together seamlessly:

How GPS Satellites Transmit Signals

Satellite signals are the foundation of the entire GPS system. They travel at the speed of light and include voluminous information about the satellite’s position and the exact time of transmission. The data is encoded into microwave signals, which are then picked up by GPS receivers. The time it takes for signals to reach the receiver is critical in calculating the distance between the satellite and the receiver.

GPS signals are transmitted on the L-Band frequency. Since the L-Band can penetrate dense clouds, fog, and other potential disruptions, it helps improve the reliability and accuracy of the GPS system.

The Role of Triangulation in GPS

A GPS receiver must acquire signals from at least four separate satellites to determine its position accurately. Receivers use a method called trilateration, which analyzes the intersection of three signals to measure distance and pinpoint its precise location. The fourth signal provides data, which helps correct any timing errors that may arise.

When discussing GPS technology, the trilateration process is commonly called “triangulation,” a more familiar term to the layperson. While this is technically incorrect, as surveyors use triangulation to measure angles and not distance, the important thing to know is that the point where three signals intersect reveals a receiver’s precise location.

How Timing Improves GPS Accuracy

Each GPS satellite is equipped with atomic clocks, which are synchronized with the official GPS ground stations. Atomic clocks provide extreme accuracy, with some advanced models able to maintain time with an error of less than one second in 300 million years or more.

Remember that the time it takes for signals to reach a receiver is a core part of GPS location calculations, and how trilateration/triangulation calculations are verified by the timing data in the fourth signal sent to each GPS receiver. When combined with the unparalleled accuracy of atomic clocks, timing data is largely responsible for GPS’s accuracy.

In fact, GPS time is so accurate that it’s used in numerous other applications, such as wireless networks, power grids, and hospitals.

What Are the Uses of GPS?

Product manufacturers and software developers continue to find new and novel uses for GPS all the time. Some of the most common GPS applications today include:

GPS for Personal Navigation

Perhaps the most common use of GPS today is personal navigation. GPS-powered navigation systems are now essentially standard equipment in today’s automobiles. Smartphone map apps provide real-time driving, walking, and bicycling directions. In either application, software developers use GPS data and public alerts to calculate the best routes and help travelers avoid road closures.

GPS for Security and Tracking

GPS technology is at the heart of several commercial tracking systems, aiding in safety and security. For example, GPS trackers can be attached to commercial vehicles, shipping containers, construction equipment, medical devices, and other valuable assets. GPS tracks shipments and deliveries in the global supply chain while helping calculate ETAs.

Crafty developers integrate GPS receivers with tamper detection systems, which can provide alerts if a thief attempts to steal a tracked asset. With GPS tracking software, these alerts become notifications on mobile devices, enabling an immediate response to theft or damage.

Other Uses for GPS

GPS has become so ubiquitous that it’s easy to miss its uses outside navigation and tracking. For instance, the data, time, and location in digital photos and videos come from GPS data. Meanwhile, thanks to GPS, scientific researchers gain valuable insights into the Earth's surface and atmosphere.

Features of Modern GPS Systems

As the uses of GPS evolve, so do the features of modern GPS systems. Years of customer feedback and advances in technology have led to more durable systems with enhanced capabilities:

Real-Time Location Updates

Modern GPS devices provide real-time location tracking rather than intermittent updates. With up-to-date and accurate location information, users can navigate with precision in cities, rural areas, or even hike through a dense forest. Real-time location updates are also key for monitoring remote assets like construction equipment or other valuables. In emergency situations, real-time data can save precious time for first responders.

Geofencing and Alert Systems

Geofencing is a software feature of modern GPS systems that defines virtual boundaries around geographical locations. When a GPS-enabled device enters or leaves a geofenced area, users can receive immediate alerts and respond accordingly. For example, parents can set up a geofence around their children’s schools to receive notifications when they arrive or leave. Businesses can monitor delivery drivers’ routes or ensure valuable assets stay in place. Geofencing can also work in conjunction with intrusion detection systems to alert when someone enters an off-limits area.

Durability and Long Battery Life

Whereas battery life plagued early GPS trackers, modern systems feature high-capacity batteries in rugged enclosures. Many devices are waterproof or water-resistant, bringing GPS tracking to fishing boats and other marine equipment. The longer battery life found in today’s GPS devices ensures they can keep up with demanding hikes or long road trips.

Global Navigation Satellite Systems (GNSS) and GPS

In discussions of GPS, you might run across the acronym GNSS. While GNSS is often presented as an alternative to GPS, that’s not entirely correct.

What Is GNSS and How Is It Different from GPS?

GNSS stands for Global Navigation Satellite System and refers to all satellite-based navigation systems currently in operation. Therefore, GNSS is not technically “different” from GPS; it’s more accurate to say GPS is just one component of the GNSS.
GNSS includes GPS, the European Union’s Galileo, Russia’s GLONASS, and China’s BeiDou Navigation Satellite System (BDS).

GPS Devices vs. GNSS Devices

When people talk about the differences between GPS and GNSS, they’re actually referring to the distinct capabilities of GPS devices and the GNSS equivalents. A GNSS-compatible device can receive signals from multiple  GNSS networks, including GPS.

How GNSS Improves Positioning Accuracy

In general, more satellites and more data equate to improved location accuracy. That makes GNSS devices a good alternative to a strictly GPS device, especially for global tracking applications outside the US.

The improved positioning accuracy comes from how a GNSS device combines signals from multiple GNSS systems. Comparing data across sources enables better error correction routines. For example, a GNSS device can compare results to check for satellite clock errors or evaluate if atmospheric disturbances might have corrupted data transmission.

How Accurate Is GPS?

In ideal conditions, GPS is incredibly accurate. However, there are factors that can negatively impact accuracy, and not all receivers are created equally.

Factors Affecting GPS Accuracy

Some of the factors that can affect the accuracy of GPS signals include:

1. Environmental Conditions: Adverse weather conditions, such as heavy rain, fog, or atmospheric disturbances, can disrupt GPS signals and reduce their accuracy.
2. Satellite Availability: The number of satellites visible to a GPS receiver, based on their arrangement above the Earth, can reduce the accuracy of location calculations.
3. Signal Interference: Tall buildings, dense foliage, mountains, and other obstructions can block or weaken GPS signals, creating less accurate positioning.

Improving GPS Precision

Fortunately, there are several ways to work around the issues that can potentially reduce GPS accuracy. One popular method is differential GPS, or DGPS. Utilizing a network of ground-based referee stations, DGPS compares raw GPS signals with the stations’ known locations to reduce the impact of positioning errors.

Assisted GPS (A-GPS) leverages cellular networks to provide additional data to GPS receivers to improve accuracy. The cell networks used in A-GPS can also speed up the time it takes for a GPS device to receive signals, which improves reliability in remote or challenging environments.

How GPS Impacts Daily Life

GPS is now a remarkably mature technology. With more than 50 years since the first Block I satellites launched, the US government, device manufacturers, and software developers have a good handle on the issues that can impact GPS accuracy. GPS is so refined that it’s become a staple in our everyday lives.

Just think of how often you use GPS for navigation. Whether it’s with a phone app, an in-car navigation system, or a dedicated receiver, it’s conceivable that you use GPS navigation daily. And it’s not just for traveling in vehicles. Exploring a new city on vacation, finding a nearby restaurant with location awareness, and hiking in a forest are all scenarios where you might turn to GPS on any given day.

At the same time, GPS makes our world safer. With accurate location information, emergency services respond to critical situations faster than ever before. GPS can quickly direct you back to safety if you find yourself lost in a new environment. When you think about it, GPS has impacted our daily lives perhaps more than any other technology. It’s now hard to imagine life without the convenience of GPS navigation, a sure sign of its ongoing importance and relevance.

Unlock the Full Potential of GPS with LandAirSea

GPS is an indispensable part of daily life, but accuracy and reliability matter. LandAirSea is a veteran in the GPS industry, and we design each product for maximum performance. To unlock the full potential of GPS for security, navigation, and tracking, shop LandAirSea’s GPS solutions for both personal and commercial use.

There are a lot of uses and options when exploring GPS trackers. If you ever feel uncertain, reach out to LandAirSea for expert advice.