Teardown: Mini GPS Jammer

If you spend enough time trolling eBay for interesting electronic devices to take apart, you’re bound to start seeing suggestions for some questionable gadgets. Which is how I recently became aware of these tiny GPS jammers that plug directly into an automotive 12 V outlet. Shipped to your door for under $10 USD, it seemed like a perfect device to rip open in the name of science.

Now, you might be wondering what legitimate uses such a device might have. Well, as far as I’m aware, there aren’t any. The only reason you’d want to jam GPS signals in and around a vehicle is if you’re trying to get away with something you shouldn’t be doing. Maybe you’re out driving a tracked company car and want to enjoy a quick two hour nap in a parking lot, or perhaps you’re looking to disable the integrated GPS on the car you just stole long enough for you to take it to the chop shop. You know, as one does.

But we won’t dwell on the potentially nefarious reasons that this device exists. Hackers have never been too choosy about the devices they investigate and experiment with, and there’s no reason we should start now. Instead, let’s take this piece of gray-area hardware for a test drive and see what makes it tick.

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Mobile Transmitter Gets Internal GPS And Bluetooth

While [Selim Olcer] was relatively happy with his Kenwood TM-D710a radio, he didn’t like the fact that it needed a bulky external GPS “backpack” for APRS location data. So he decided to crack open the head unit and see if he couldn’t integrate his own GPS hardware (machine translation). Not only did he succeed, but he even threw in Bluetooth compatibility for good measure.

With the repair manual circuit diagrams in hand, it was no problem to find the GPS RX and TX lines that were being broken out to the external connector. Unfortunately, the radio’s electronics are all 5 volts and the GPS module [Selim] wanted to use was only 3.3 V. So he came up with a small PCB that included not only the voltage regulator to power the GPS module, but also some voltage-dividers to level shift those signals.

Since the Kenwood TM-D710a was already designed to accept a GPS upgrade module, he just needed to change some configuration options in the radio’s menus for it to see the new hardware. Technically the project was done at this point, but since there was still room in the case and he had a GPS module spitting out NMEA sentences, [Selim] tacked on a common Bluetooth serial module so he could see the position information on his smartphone. With an application like APRSdroid, he now has a nice moving map display using the position pulled from the radio’s GPS.

With this modification done it looks like the head unit is ready to go, but that’s only the beginning for a mobile rig. Now we want to see how he integrates the whole thing into the car.

Draw On Your Lawn With This Autonomous Mower And RTK-GPS

The rise of open source hardware has seen a wide variety of laborious tasks become successfully automated, saving us humans a great deal of hassle.  Suffice to say, some chores are easier to automate than others. Take the classic case of a harmless autonomous vacuum cleaner that can be pretty dumb, bumping around the place to detect the perimeter as it traverses the room blindly with a pre-programmed sweeping pattern.

Now in principle, this idea could be extended to mowing your lawn. But would you really want a high speed rotating blade running rampant as it aimlessly ventures outside the perimeter of your lawn? The Sunray update to the Ardumower autonomous lawn mower project has solved this problem without invoking the need to lay down an actual perimeter wire. As standard consumer grade GPS is simply not accurate enough, so the solution involves implementing your very own RTK-GPS hardware and an accompanying base station, introducing centimeter-level accuracy to your mowing jobs.

RTK-GPS, also known as Carrier Phase Enhanced GPS, improves the accuracy of standard GPS by measuring the error in the signal using a reference receiver whose position is known accurately. This information is then relayed to the Ardumower board over a radio link, so that it could tweak its position accordingly. Do you need the ability to carve emojis into your lawn? No. But you could have it anyway. If that’s not enough to kick off the autonomous lawnmower revolution, we don’t know what is.

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How To Choose The Right GPS Module For Your Project

You’ve built a brand new project, and it’s a wonderful little thing that’s out and about in the world. The only problem is, you need to know its location to a decent degree of accuracy. Thankfully, GPS is a thing! With an off-the-shelf module, it’s possible to get all the location data you could possibly need. But how do you go about it, and what parts are the right ones for your application? For the answers to these questions, read on! Continue reading “How To Choose The Right GPS Module For Your Project”

Busting GPS Exercise Data Out Of Its Garmin-controlled IoT Prison

If you take to the outdoors for your exercise, rather than walking the Sisyphusian stair machine, it’s nice to grab some GPS-packed electronics to quantify your workout. [Bunnie Huang] enjoys paddling the outrigger canoe through the Singapore Strait and recently figured out how to unpack and visualize GPS data from his own Garmin watch.

By now you’ve likely heard that Garmin’s systems were down due to a ransomware attack last Thursday, July 23rd. On the one hand, it’s a minor inconvenience to not be able to see your workout visualized because of the system outage. On the other hand, the services have a lot of your personal data: dates, locations, and biometrics like heart rate. [Bunnie] looked around to see if he could unpack the data stored on his Garmin watch without pledging his privacy to computers in the sky.

Obviously this isn’t [Bunnie’s] first rodeo, but in the end you don’t need to be a 1337 haxor to pull this one off. An Open Source program called GPSBabel lets you convert proprietary data formats from a hundred or so different GPS receivers into .GPX files that are then easy to work with. From there he whipped up less than 200 lines of Python to plot the GPS data on a map and display it as a webpage. The key libraries at work here are Folium which provides the pretty browsable map data, and Matplotlib to plot the data.

These IoT devices are by all accounts amazing, listening for satellite pings to show us how far and how fast we’ve gone on web-based interfaces that are sharable, searchable, and any number of other good things ending in “able”. But the flip side is that you may not be the only person seeing the data. Two years ago Strava exposed military locations because of an opt-out policy for public data sharing of exercise trackers. Now Garmin says they don’t have any indications that data was stolen in the ransomware attack, but it’s not a stretch to think there was a potential there for such a data breach. It’s nice to see there are Open Source options for those who want access to exercise analytics and visualizations without being required to first hand over the data.

Not Just GPS: New Options For Global Positioning

A few weeks ago, China launched the final satellite in its BeiDou-3 satellite positioning system. Didn’t know that China had its own GPS? How about Europe’s Galileo, Russia’s GLONASS, or Japan’s QZSS? There’s a whole world of GPS-alikes out there. Let’s take a look.

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Number Crunching GPS For The DIYer

Many of us have had cause to add GPS to a project, whether it’s because we need an accurate timebase or just want to know where the bloody thing is. Normally, this consists of plugging in a cheap module and making sure the antenna has a good view of the sky. [Mike] wanted to dig deeper, however, and figure out just what goes into decoding a GPS signal and calculating a location fix.

[Mike]’s investigation combined several avenues of investigation. In terms of decoding live radio signals, he selected a KiwiSDR software defined radio. Combined with a Digilent Nexys 2 FPGA, it was now possible to get live data off the air and into the PC quickly for decoding. In concert with this, [Mike] used a sample of raw GPS data captured in Nottingham, UK in order to test his code. After much experimentation, [Mike] was able to get the data decoded with 700 lines of C code. Decoding three minutes worth of data took all night, but further development allowed things to be sped up over 200 times. For the curious, the code is up on Github to convert raw ADC samples into actual location fixes.

Armed with the wealth of resources online and the right hardware, [Mike] was sucessfully able to achieve his goal, and figure out just precisely where his house is, to boot. As a bonus, the whole project was inspired by a similar project posted in these very pages back in 2013! If you’re working on your own satellite-based projects, be sure to drop us a line.