Affordable Ground-Penetrating Radar

October 22, 2020 by Bryan Cockfield 30 Comments

While you might think of radar pointing toward the skies, applications for radar have found their way underground as well. Ground-penetrating radar (GPR) is a tool that sends signals into the earth and measures their return to make determinations about what’s buried underground in much the same way that distant aircraft can be located or identified by looking for radar reflections. This technology can also be built with a few common items now for a relatively small cost.

This is a project from [Mirel] who built the system around a Arduino Mega 2560 and antipodal Vivaldi antennas, a type of directional antenna. Everything is mounted into a small cart that can be rolled along the ground. A switch attached to the wheels triggers the radar at regular intervals as it rolls, and the radar emits a signal and listens to reflections at each point. It operates at a frequency range from 323 MHz to 910 MHz, and a small graph of what it “sees” is displayed on an LCD screen that is paired to the Arduino.

Using this tool allows you to see different densities of materials located underground, as well as their depths. This can be very handy when starting a large excavation project, detecting rock layers or underground utilities before digging. [Mirel] made all of the hardware and software open-source for this project, and if you’d like to see another take on GPR then head over to this project which involves a lot of technical discussion on how it works.

Recognizing Activities Using Radar

September 6, 2020 by Danie Conradie 10 Comments

Caring for the elderly and vulnerable people while preserving their privacy and independence is a challenging proposition. Reaching a panic button or calling for help may not be possible in an emergency, but constant supervision or camera surveillance is often neither practical nor considerate. Researchers from MIT CSAIL have been working on this problem for a few years and have come up with a possible solution called RF Diary. Using RF signals, a floor plan, and machine learning it can recognize activities and emergencies, through obstacles and in the dark. If this sounds familiar, it’s because it builds on previous research by CSAIL.

The RF system used is effectively frequency-modulated continuous-wave (FMCW) radar, which sweeps across the 5.4-7.2 GHz RF spectrum. The limited resolution of the RF system does not allow for the recognition of most objects, so a floor plan gives information on the size and location of specific features like rooms, beds, tables, sinks, etc. This information helps the machine learning model recognize activities within the context of the surroundings. Effectively training an activity captioning model requires thousands of training examples, which is currently not available for RF radar. However, there are massive video data sets available, so researchers employed a “multi-modal feature alignment training strategy” which allowed them to use video data sets to refine their RF activity captioning model.

There are still some privacy concerns with this solution, but the researchers did propose some improvements. One interesting idea is for the monitored person to give an “activation” signal by performing a specified set of activities in sequence.

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Damage To Arecibo Leaves Gaping Hole In Astronomy

August 24, 2020 by Tom Nardi 69 Comments

In the early morning hours of August 10th, a support cable at the Arecibo Observatory pulled lose from its mount and crashed through the face of the primary reflector below. Images taken from below the iconic 305 meter dish, made famous by films such as Contact and GoldenEye, show an incredible amount of damage. The section of thick cable, estimated to weigh in at around 6,000 kilograms (13,000 pounds), had little difficulty tearing through the reflector’s thin mesh construction.

Worse still, the cable also struck the so-called “Gregorian dome”, the structure suspended over the dish where the sensitive instruments are mounted. At the time of this writing it’s still unclear as to whether or not any of that instrumentation has been damaged, though NASA at least has said that the equipment they operate inside the dome appears to have survived unscathed. At the very least, the damage to the dome structure itself will need to be addressed before the Observatory can resume normal operations.

The Arecibo Observatory by JidoBG [CC-BY-SA 4.0]

But how long will the repairs take, and who’s going to pay for them? It’s no secret that funding for the 60 year old telescope has been difficult to come by since at least the early 2000s. The cost of repairing the relatively minor damage to the telescope sustained during Hurricane Maria in 2017 may have been enough to shutter the installation permanently if it hadn’t been for a consortium led by the University of Central Florida. They agreed to share the burden of operating the Observatory with the National Science Foundation and put up several million dollars of additional funding.

It’s far too early to know how much time and money it will take to get Arecibo Observatory back up to operational status, but with the current world situation, it seems likely the telescope will be out of commission for at least the rest of the year. Given the fact that repairs from the 2017 damage still haven’t been completed, perhaps even longer than that. In the meantime, astronomers around the globe are left without this wholly unique resource.

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Faux Radar Uses Ultrasound & Python

July 18, 2020 by Lewin Day 25 Comments

Radars are simply cool, and their portrayal in movies and TV has a lot to do with that. You get a sweet glowing screen that shows you where the bad guys are, and a visual representation of your missiles on their way to blow them up. Sadly, or perhaps thankfully, day to day life for most of us is a little less exhilarating. We can make do with a facsimile of the experience instead.

The project consists of an Arduino Uno outfitted with an ultrasound module that can do basic range measurements on the order of tens of centimeters. The module is then placed on a servo and scanned through a 180 degree rotation. This data is passed back to a computer running a Python application, which plots the results on a Plan Position Indicator, or PPI – the sweeping display we’re all so familiar with.

While it’s unlikely you’ll be using such a setup to engage bandits, it could prove as a useful module for robot navigation or similar applications. We’ve seen ultrasonic transducers used for exactly that. Video after the break.

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Wind Farms In The Night: On-Demand Warning Lights Are Coming

March 24, 2020 by Sven Gregori 117 Comments

There appears to be no shortage of reasons to hate on wind farms. That’s especially the case if you live close by one, and as studies have shown, their general acceptance indeed grows with their distance. Whatever your favorite flavor of renewable energy might be, that’s at least something it has in common with nuclear or fossil power plants: not in my back yard. The difference is of course that it requires a lot more wind turbines to achieve the same output, therefore affecting a lot more back yards in total — in constantly increasing numbers globally.

Personally, as someone who encounters them occasionally from the distance, I find wind turbines mostly to be an eyesore, particularly in scenic mountainous landscapes. They can add a futuristic vibe to some otherwise boring flatlands. In other words, I can not judge the claims actual residents have on their impact on humans or the environment. So let’s leave opinions and emotions out of it and look at the facts and tech of one issue in particular: light pollution.

This might not be the first issue that comes to mind when thinking about wind farms. But wind turbines are tall enough to require warning lights for air traffic safety, and can be seen for miles, blinking away in the night sky. From a pure efficiency standpoint, this doesn’t seem reasonable, considering how often an aircraft is actually passing by on average. Most of the time, those lights simply blink for nothing, lighting up the countryside. Can we change this?

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Teardown: Cobra XRS 9740 Radar Detector

March 18, 2020 by Tom Nardi 46 Comments

Drivers with a lead foot more often than not have Waze open on their phone so they can see if other drivers have spotted cops up ahead. But avoiding a speeding ticket used to involve a lot more hardware than software. Back before the smartphone revolution, that same driver would have had a radar detector on their dashboard. That’s not to say the gadgets are completely unused today, but between their relatively high cost (one of the top rated models on Amazon as of this writing costs over $300) and the inevitable false positives from so many vehicles on the road having their own radar and LIDAR systems, they’ve certainly become a less common sight over the years

The subject of today’s teardown is a perfect example of “Peak Radar Detector”. Manufactured back in 2007, the Cobra XRS 9740 would have been a fairly mid-range entry offering the sort of features that would have been desirable at the time. Over a decade ago, having an alphanumeric display, voice alerts, and a digital compass were all things worth shouting about on the box the thing was sold in. Though looking like some kind of Cardassian warship was apparently just an added bonus.

As the name implies these devices are primarily for detecting radar activity, but by this point they’d also been expanded to pick up infrared lasers and the strobe beacons on emergency vehicles. But false positives were always a problem, so the device allows the user to select which signals it should be on the lookout for. If you were getting some kind of interference that convinced the detector it was being bombarded with IR lasers, you could just turn that function off without having to pull the plug entirely.

But it’s important to remember that this device was built back when people were still unironically carrying around flip phones. Detecting laser and multi-band radars might sound like something pulled from the spec sheet of a stealth fighter jet, but this is still a piece of consumer electronics from more than a decade in the past. So let’s crack it open and take a look at what goes on inside a radar detector that’s only a few years away from being old enough to get its own driver’s license.

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Just How Can You Lose Something The Size Of A Cargo Ship?

February 26, 2020 by Jenny List 91 Comments

I’m writing from a cozy farmhouse just outside of Oxford, UK where we are slowly emerging from a particularly intense Atlantic storm. Some areas have widespread flooding, while fallen tree branches and damaged roofs are countrywide. Our neighbours in the Irish Republic are first in the path of these storms, and receive an especially strong pasting.

In the news following the storm is a merchant ship that was washed up by this storm on the coast of County Cork. The MV Alta is a nearly 2300t and 77m (just over 253 ft) freighter that had been abandoned in 2018 south of Bermuda after a mechanical failure had rendered it incapable of navigation. Its crew had been rescued by the US Coast Guard, and since then — apart from a brief sighting in mid-Atlantic by a Royal Navy polar research vessel — it had passed unseen as a drifting ghost ship before appearing on the Irish coast.

In a very literal sense it had dropped off the radar, but the question for us is how? With the huge array of technological advances in both navigation aids and global sensing available at the end of the 21st century’s second decade, should that even be possible? It’s worth taking a while as land-lubbers to look at how ships are tracked, to try to make sense of the seeming invisibility of something that is after all pretty large and difficult to hide.

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