Increasing Local GPS Accuracy For A Small Robot

June 25, 2026 by Bryan Cockfield 32 Comments

Even though GPS makes it possible for us to easily navigate around the planet in almost any vehicle we’d like, whether that’s a passenger vehicle, airplane, or cargo ship, it’s not really suitable for applications that require sub-meter accuracy. For that, some specialized hardware is needed, and [GreatScott!] shows us how to do it using a small robot as a platform.

The key to extremely accurate GPS signals in this case is using a receiver that supports real-time kinematic positioning (RTK). This type of system relies on a base station with a known position communicating with local mobile receivers to increase the precision of those mobile receivers by comparing the phase angle of the received signals. Of course these modules are much more expensive than the average standard GPS receiver, but for this kind of accuracy there is always a cost.

After getting a baseline accuracy of around two meters with a standard GPS receiver, [GreatScott!] installs the RTK GPS mobile receiver on a tracked robotic platform and a base station on a fence post. With the RTK system running, the limiting factor in accuracy became the robot’s steering system, as its turning radius and steering algorithms weren’t up to the task of hitting centimeter-sized targets out of the box.

But, as a proof-of-concept, it goes to show how accurate GPS can be as long as the right hardware is used, and for practical applications is good enough to mow a lawn with a robot or even do some amateur land surveying.

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Long-Theorized GPS Weakness Exploited On Large Scale

June 23, 2026 by Bryan Cockfield 40 Comments

GPS has become fairly common in our everyday lives, not only able to pinpoint our locations on Earth but also as an incredibly accurate timekeeping method. But since these satellites are around 20,000 km above Earth, the received signals on the surface of the planet can be incredibly weak. This makes them prone to jamming and spoofing, a weakness of the technology that has long been known. Although attempts to mitigate these problems have been ongoing, there has recently been a large-scale attempt to interfere with these signals that put all mitigation efforts to the test.

One proposed way to improve resilience is to supplement existing GNSS systems with low-Earth-orbit navigation satellites. In this example, a company called Xona is using a satellite called Pulsar-0 that operates in low-Earth orbit (LEO) and provides positioning and timing signals that are around 100 times stronger than standard signals from GPS/GNSS satellites. It is able to receive GPS signals as well, ensuring the two systems agree on one another. And, because Pulsar’s navigation signals originate from LEO and are much stronger than conventional GNSS signals, Xona expects them to be significantly more resistant to jamming.

Beyond geopolitics, spoofing GPS has some applications in finding legendaries in Pokemon Go as well as making it fairly trivial to steal GPS-guided drones.

An In-Browser Visualizer For GPS Satellites

June 18, 2026 by Zoe Skyforest 9 Comments

Billions of people use GPS on a daily basis, along with the various other satellite navigation systems available today. But few of us spend much time contemplating the fleet of satellites above us that actually makes the system work. [Robert Wolf] has, though, and he’s built a simple visualizer that displays just what those space birds are doing at any given time.

The visualizer runs right in the browser, and displays a cluster of GPS satellites in a 3D view around the Earth. The tool also offers a list of satellites and related data, including signal-to-noise ratio of the received signals from each one, and the ability to play back satellite positions from previous days. The satellite positions are captured from a GPS receiver that [Robert] operates in the UK.

The view isn’t global or complete, since the receiver can only see a certain number of satellites from its location, but it nevertheless gives an idea of where a subset of GPS satellites are flying above the globe. Depending on the selected view, it’s possible to see the satellites superimposed over the world map itself — or from a distant observer’s perspective, as if looking at the Earth from a distance, among other options.

If you’ve ever wanted an intuitive idea about where the GPS satellites live, this tool is a great way to understand it. We’ve also previously discussed the wide range of GPS alternatives that have been developed over the years. If you’ve got your own GPS hacks brewing in the home lab, don’t hesitate to let us know on the tipsline.

Spy Tech: The GPS Numbers Station

June 8, 2026 by Al Williams 24 Comments

We’ve talked before about number stations — mysterious shortwave transmitters repeating numbers, presumably for clandestine purposes. But, of course, the mere fact that they are unusual makes them stand out. The best place to hide something is in plain sight. In the old days, a broadcaster might slip a fake news story in mentioning a name that has a secret meaning, for example. But according to [Steven Murdoch], the United States has an even more obvious hiding place for a numbers station: inside GPS.

Every L1 C/A navigation message is a 176-bit field known by the affectionate moniker: Subframe 4, Page 17. The GPS specification says it is for “special messages.” No one has disclosed what those messages might be.

[Murdoch] at University College London analyzed over 12 million GPS packets from 2007 to 2026, trying to understand what was in this field. You might think 176 bits isn’t much, and you are right. But the L1 C/A signal carries 50 bits per second, and each frame is 1,500 bits. As [Murdoch] points out: “every bit must earn its place.” Each subframe is 300 bits, so this mysterious signal is 12% of the subframe. It must be important to someone.

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There’s More To Global Positioning Than Just GPS

May 7, 2026 by Tom Nardi 18 Comments

The Global Positioning System (GPS) was developed by the United States military in the 1970s, but it wasn’t long before civilians all over the planet started using it. By the early 2000s the technology was popping up in consumer devices such as mobile phones, and since then its become absolutely integral to our modern way of life.

But although support for GPS in our gadgets is nearly ubiquitous, it’s not the only option when it comes to figuring out where you are on the globe. As you might imagine, not everyone was thrilled with building their infrastructure around one of Uncle Sam’s pet projects, and so today there are several homegrown regional and global satellite navigation systems in operation.

As a follow-up to our recent dive into the ongoing GPS upgrades, let’s take a look at some of the other satellite positioning systems and who operates them.

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The GPS III Rollout Is Almost Complete, But What Is It?

April 28, 2026 by Tom Nardi 34 Comments

Considering how integral it is to our modern way of life, you could be excused for thinking that the Global Positioning System (GPS) is a product of the smartphone era. But the first satellites actually came online back in 1978, although the system didn’t reach full operational status until April of 1995. While none of the active GPS satellites currently in orbit are quite that old, several of them were launched in the early 2000s — and despite a few tweaks and upgrades, their core technology isn’t far removed from their 1990s era predecessors.

But in the coming years, that’s finally going to change. Just last week, the tenth GPS III satellite was placed in orbit by a SpaceX Falcon 9 rocket. Once it’s properly configured and operational, it will join its peers to form the first complete “block” of third-generation GPS satellites. Over the next decade, as many as 22 revised GPS III satellites are slated to take their position over the Earth, eventually replacing all of the aging satellites that billions of people currently rely on.

So what new capabilities do these third-generation GPS satellites offer, and why has it taken so long to implement needed upgrades in such a critical system?

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Laser Ranging Makes GPS Satellites More Accurate

March 29, 2026 by Maya Posch 25 Comments

Although GNSS systems like GPS have made pin-pointing locations on Earth’s sphere-approximating surface significantly easier and more precise, it’s always possible to go a bit further. The latest innovation involves strapping laser retroreflector arrays (LRAs) to newly launched GPS satellites, enabling ground-based lasers to accurately determine the distance to these satellites.

Similar to the retroreflector array that was left on the Moon during the Apollo missions, these LRAs will be most helpful with scientific pursuits, such as geodesy. This is the science of studying Earth’s shape, gravity and rotation over time, which is information that is also incredibly useful for Earth-observing satellites.

Laser ranging is also essential for determining the geocentric orbit of a satellite, which enables precise calibration of altimeters and increasing the accuracy of long-term measurements. Now that the newly launched GPS III SV-09 satellite is operational this means more information for NASA’s geodesy project, and increased accuracy for GPS measurements as more of its still to be launched satellites are equipped with LRAs.