AI-Powered Bumper Sticker Provides Context-Sensitive Urban Camouflage

While we absolutely support the right of everyone to express their opinions, it seems to us that it’s rarely wise to turn your vehicle into a mobile billboard for your positions. Aside from potentially messing up the finish on your car, what’s popular and acceptable at home might attract unwanted attention while traveling abroad, leading to confrontations that might make your trip a little more eventful than it needs to be.

So why not let technology help you speak your mind in a locally sensitive manner? That’s the idea behind [Pegor]’s “smahtSticker”, an AI-powered bumper sticker that provides the ultimate in context-sensitive urban camouflage. The business end of smahtSticker — we’re going to go out on a limb here and predict that [Pegor] hails from the Boston area — is an 8.8″ (22-cm) wide HDMI display capable of 1920×480 resolution. That goes on the back of your car and is driven by a Raspberry Pi Zero with a GPS module. The Pi grabs a geolocation every second, and if you’ve moved more than 25 feet (7.6 m) — political divisions are at least that granular in the US right now, trust us — it grabs your current ZIP code using GeoPy. That initiates a query to the OpenAI API to determine the current political attitudes in your location, which is used to select the right slogan to display. You’ll fit in no matter where you wander — wicked smaht!

Now, of course, this is all in good fun, and with tongue planted firmly in cheek. The display isn’t weatherized at all, so that would need to be addressed if one felt like fielding this. Also, ZIP codes may be good for a lot of things, but it’s not the best proxy for political alignment, so you might want to touch that part up.

How Airplanes Mostly Stopped Flying Into Terrain And Other Safety Improvements

We have all heard the statistics on how safe air travel is, with more people dying and getting injured on their way to and from the airport than while traveling by airplane. Things weren’t always this way, of course. Throughout the early days of commercial air travel and well into the 1980s there were many crashes that served as harsh lessons on basic air safety. The most tragic ones are probably those with a human cause, whether it was due to improper maintenance or pilot error, as we generally assume that we have a human element in the chain of events explicitly to prevent tragedies like these.

Among the worst pilot errors we find the phenomenon of controlled flight into terrain (CFIT), which usually sees the pilot losing track of his bearings due to a variety of reasons before a usually high-speed and fatal crash. When it comes to keeping airplanes off the ground until they’re at their destination, here ground proximity warning systems (GPWS) and successors have added a layer of safety, along with stall warnings and other automatic warning signals provided by the avionics.

With the recent passing of C. Donald Bateman – who has been credited with designing the GPWS – it seems like a good time to appreciate the technology that makes flying into the relatively safe experience that it is today.

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Navigate Burning Man With Ease With This Custom Tool

When setting up a city in the desert, the team behind Burning Man does its best to lay things out in an ordered fashion. Even still, getting around at ground level can be a challenge at times, and it’s easy to get lost. To help get around easier, [Zach] developed a nifty GPS device built specifically for navigating the ephemeral clock-like city.

The device is built for a few simple purposes. It shows where you are, it helps you navigate somewhere you’ve been before, and it helps you navigate to portable toilets. It’s set up to be usable both on bike and on foot, the typical ways of getting around the playa. Since Black Rock City is fairly simple, it uses an arrow to point to a desired waypoint, and is capable of storing up to five points of interest. It’s built using a cheap GNSS receiver and transflective LCD screen, and a Pi Pico is the brains of the operation.

The value of the device is obvious, particularly when exploring deeper areas of the playa, or after the road signs have been removed or structures have been taken down or burnt to ashes. We’ve seen some other great projects from the desert festival before, too. If you’ve got your own playa-spec hacks, don’t hesitate to let us know!

FLOSS Weekly Episode 767: Owntracks, Are We There Yet?

This week Jonathan Bennett and Jeff Massie talk with JP Mens about Owntracks, the collection of programs that lets you take back control of your own location data. It’s built around the simple idea of taking position data from a mobile phone or other data source, sending it over MQTT to a central server, and logging that data to a simple data store.

From there, you can share it as trips, mark points of interest, play back your movement in a web browser, and more. And because it’s just JSON inside MQTT, it’s pretty trivial to make a connector to interface with other projects, like Home Assistant. We’ve even covered the process!

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Cockpit of a Hawker Siddeley Trident with the moving map display

A Live Map Display In A 1960s Airliner

We tend take GPS navigation for granted these days, so it’s easy to forget that it became only available in the last few decades. Aviation navigation used to be significantly more challenging, so how was the Hawker Siddeley Trident, a 1960s airliner, fitted with a live updating map display? In a fascinating dive into aviation history the British Airliner Collection has spun up an insightful article on the magic behind these moving map displays.

Without access to satellite navigation or advanced electronics, engineers had to get creative. Enter the Trident’s moving map display, a marvel of ingenuity that predated the GPS systems. Using a combination of Doppler radar and some clever mechanics, pilots could accurately determine their position without relying on any external signals.

The system makes use of four Doppler radar beams, arranged in what was known as the Janus array. This configuration corrected for errors caused by changes in altitude or wind drift, ensuring accurate ground speed readings. The movable antennas mounted under the cabin floor could adjust its orientation to maintain alignment with the actual direction of travel, calculating drift angle precisely. Combined with compass information and flight time from a known start point to to indicate the current position with a pointer on a rolled paper map. The system was well ahead of it’s time, and significantly easier to use and more accurate than the Decca radio navigation system in use at the time.

It’s mind boggling to see the solutions engineers came up with without much of the digital technology we take for granted today. Gyroscopes for inertial navigation, the cavity magnetron for radar and radial engines were all building blocks for modern aviation.

Thanks for the tip [poiuyt]!

A Homebrew GPS Correction System For DIY Land Surveying

For those of you rushing to the comment section after reading the title to tell [Ben Dauphinee] that his DIY land surveying efforts are for naught because only a licensed surveyor can create a legally binding property description, relax — he already knows. But what he learned about centimeter-resolution GPS is pretty interesting, especially for owners of large rural properties like him.

[Ben]’s mapping needs are less rigorous than an official survey; he just wants to get the locations of features like streams and wood lines, and to get topographic elevations so that he has a general “lay of the land” for planning purposes. He originally engaged a surveyor for that job, but after shelling out $4,600 to locate a single property line, he decided to see what else could be done. Luckily, real-time kinematics, or RTK, holds the key. RTK uses a fixed GPS station to provide correction signals to a mobile receiver, called a rover. If the fixed station’s position is referenced to some monument of known position, the rover’s position can be placed on a map to within a couple of centimeters.

To build his own RTK system, [Ben] used some modules from SparkFun. The fixed station has an RTK breakout board and a multi-band GNSS antenna to receive positioning data, along with a Raspberry Pi to run the RTK server. An old iPhone with a prepaid SIM provides backhaul to connect to the network that provides correction data. [Ben]’s rover setup also came mainly from SparkFun, with an RTK Facet receiver mounted on a photographer’s monopod. Once everything was set up and properly calibrated, he was able to walk his property with the rover and measure locations to within 4 centimeters.

This was not an inexpensive endeavor — all told, [Ben] spent about $2,000 on the setup. That’s a lot, especially on top of what he already paid for the legal survey, but still a fraction of what it would have cost to have a surveyor do it, or to buy actual surveyor’s equipment. The post has a ton of detail that’s worth reading for anyone interested in the process of mapping and GPS augmentation.

Building A GPS Receiver From The Ground Up

One of the more interesting facets of GPS is that, at least from the receiver’s point-of-view, it’s a fairly passive system. All of the information beamed down from the satellites is out in the ether, all the time, free for anyone on the planet to receive and use as they see fit. Of course you need to go out and buy a receiver or, alternatively, possess a certain amount of knowledge to build a circuit that can take those signals and convert them into something usable. Luckily, [leaning_tower] has the required knowledge and demonstrates it with this DIY GPS receiver.

This receiver consists of five separate circuit boards, all performing their own function. The first, a mixer board, receives the signal via an active antenna and converts it to a lower frequency. From there it goes to a second mixer and correlation board to compare the signal to a local reference, then a signal processing board that looks at this intermediate frequency signal to make sense of the data its seeing. Finally, an FPGA interfacing board ties everything together and decodes the information into a usable form.

Dealing with weak signals like this has its own set of challenges, as [leaning_tower] found out. The crystal oscillator had to be decapped and modified to keep from interfering with the GPS radio since they operated on similar frequencies. Even after ironing out all the kinks, the circuit takes a little bit of time to lock on to a specific satellite but with a second GPS unit for checking and a few weeks of troubleshooting, the homebrew receiver is up and running. It’s an impressive and incredibly detailed piece of work which is usually the case with sensitive radio equipment like GPS. Here’s another one built on a Raspberry Pi with 12 channels and a pretty high accuracy.