Today, self-driving semi-trucks are rapidly rolling out onto public highways. From the East Coast to the West Coast, autonomous 18-wheelers have launched out of the closed-course phase and into the public roads testing phase. At Torc, we get asked a ton of questions about how these autonomous trucks are getting around: do autonomous vehicles use GPS? How do self-driving cars know where they are? Do Torc’s self-driving trucks use GPS? If so, do they use the same systems that we do?

While Torc’s self-driving semi-trucks don’t use the kinds of GPS systems that narrate our family road trips, they do use their own form of GPS. However, this isn’t the only tool autonomous trucks have when it comes to navigation. Instead, they use a host of location-finding hardware and software to find their way around. With these add-ons assisting our self-driving vehicles, they’re able to be more efficient and more accurate in their driving decision-making. Our autonomous systems are totally self contained and do not need continuous satellite connects to safely complete its mission.

Whether they’re moving freight from coast-to-coast or just heading to the next state over, GNSS and GPS systems allow trucks like ours to get around without sacrificing safety or speed. In fact, they improve both speed and safety while adding an extra layer of efficiency to all routes.

What is GNSS?

GNSS, or Global Navigation Satellite System, is where an autonomous semi-truck’s navigation system begins. Across our Earth’s orbit, several satellites are strategically placed in constellation-like formats. Each satellite transmits a particular signal, which we can connect to via GNSS receivers. This signal tells our devices where we are in relation to those satellites, allowing us to decode our locale via this information and trilateration.

With the help of careful engineering and countless years of innovation, we’re able to connect to these satellites to get us from work, to school, and to all the in-betweens. For autonomous trucks, this connection means that they can identify their locations at all times, respond to remote operator’s requests to change course, and more.

GPS vs. GNSS

Some people refer to GNSS and GPS interchangeably, but they’re not technically one in the same.

Like we talked about above, GNSS uses constellations of satellites based on the concept of trilateration, but which constellation your GNSS will use is determined by your own location. If you’re in North America, your GNSS system likely uses GPS, or the Global Positioning System: a collection of 31 satellites that orbit around the Earth. If you’re in Europe, your GNSS system will use Galileo, a separate set of satellites positioned over the European continent. There are also GlONASS and BeiDou, which serve Russia and the Asian-Pacific, respectively.

Therefore: GNSS can be used interchangeably with the phrase, “GPS”, but someone in Russia might use “GIONASS” just as interchangeably.

How do autonomous trucks use GNSS to get around?

The GNSS system that serves our self-driving 18-wheelers uses some of the tools that our everyday navigation apps use, but it’s just one piece of the self-driving puzzle.

Simple-navigation GPS, like the apps that we pull up on our phones, often have limited accuracy and reliability. If you’ve ever been using a GPS app while driving down a road and watched your car icon suddenly zoom in a different direction, you’ve likely experienced this. In the same vein, you might’ve watched your app “recalculate location” for a moment too long, causing you to miss your turn. When we use simple-navigation systems in our day-to-day lives, these kinds of issues are just mild inconveniences. However, autonomous semi-trucks need more sophisticated problem-solving to ensure that they’re able to meet supply chain demands and safety requirements.

GPS systems, including the ones used by our autonomous 18-wheelers, supplement their satellite solutions with maps and historical information. Some of those apps that we use in our own lives also use maps and historical information; it’s part of the reason why those recalculation issues don’t crop up too often for most of us, but those that drive in rural areas might have more experience with those zooming-icon incidents. Autonomous trucks use this historical data, but continue to go a step further by adding an IMU system, or an inertial measurement unit system.

An IMU is a device that can measure and report specific gravity and angular rate of an object to which it is attached. They typically contain a gyroscope and an accelerometer, which allow them to measure angular rate and force/acceleration. In the case of autonomous trucks, an IMU might tell a truck how fast it’s traveling or, in combination with other sensors, what angle a street sign is hanging at.

Together, GNSS and IMU team up to create motion estimation, allowing a self-driving truck to assess its surroundings with as much accuracy as possible.

Complex algorithms are written to continue determining the vehicle’s position for extended periods of time if a GNSS outage happens. This helps us to confidently get the vehicle to a safe state even if all our satellites disappear in a blink.

Do autonomous trucks use GPS?

Yes! Autonomous vehicles do use GPS, but it’s not the same system that most of us use on a day-to-day basis. They have a ton of other tools available to supplement their satellite-based navigation systems, allowing them to “see” their surroundings with far more accuracy than our human abilities. With high-tech add-ons like IMUs, sensors, maps, and historical data, autonomous trucks are able to navigate our highway roads with heightened accuracy.

Whether self-driving semi-trucks are heading to a California hub or a Florida-based shipping center, these trucks have the unique ability to pilot through a wide array of places, states, and more.