4 ms·
"... It helps to think of it just as your brain’s interpretation of a two dimensional representation of the coherent sum of backscatter responses from electroma
by supernova87a 6y ago
"... It helps to think of it just as your brain’s interpretation of a two dimensional representation of the coherent sum of backscatter responses from electromagnetic waves..."
Well that clears it right up, thanks! Lol.
I'm pleased that they think any general public person or even journalist is capable of seeing the difference between the left and right figure in the article.
- mekkkkkk 6y agoI was about to write this same thing. It is amazing to me how scientists/experts sometimes seem utterly incapable to level with an audience. I get that it's tough if there is a lot of ground to cover, but the quote you pulled is so telling. Those who are now convinced that the NSA are looking at them from space when they shower will probably gain absolutely nothing from this release.
- excerionsforte 6y agoLol. Articles like this remind me of Silicon Valley where Pied Piper app is built for engineers rather than "Regular people": https://www.youtube.com/watch?v=QYBcLMiR9b0 https://www.youtube.com/watch?v=QYBcLMiR9b0 and then Richard going in to the focus group trying to explain it science-speak rather than ELI5. It seemed like this article's intended audience is regular people and it missed the mark. First question I had was... what is SAR?
- Animats 6y agoSynthetic Aperture Radar. What you're really seeing here is what happens when you try to put together a 3D image from an angled line scan from a moving scanner. There isn't enough information to do this perfectly, so you get artifacts on tall objects. You can see somewhat similar artifacts in Google Earth when looking down on tall objects for which they don't have full elevation data, like trees. What's impressive is that they're getting 50cm resolution from orbit. Doing this from aircraft is nothing new; that's been going on for decades. But 50cm from a satellite? That's an achievement.
- andi999 6y agoI read it is 50cm because it is the legal (not technical) limit.
- derstander 6y agoIn some sense achieving high resolution imagery from orbit is simpler in that SAR requires motion compensation on the order of a wavelength. Planes are subject to all sorts of motion like turbulence whereas a satellite’s motion is often far more predictable. Closing the link budget can certainly be more challenging given longer ranges and size, weight, power, and cooling constraints for satellites though.
- nick_kline 6y agoReading that long article where the writer didn't have awareness that they should define that term reminds me of reading in grad school. Please define the main term in your articles, people! Geeze.
- derstander 6y agoRadar is good at ranging. So you can locate things precisely in that dimension. It’s not great at cross-range though because a beam is typically wide. SAR gets around this by essentially using the flight path or orbit of a radar sensor to synthesize a longer antenna than you’ve got. You make some assumptions that can be violated to varying degrees that may degrade the image (you need coherence over the synthetic aperture, you assume things you’re imaging don’t move, etc.)
- p5a0u9l 6y agoConsider a simple radar as capable of locating objects in 3D spherical coordinates- range, azimuth, and elevation. Radar is typically really good at measuring distance, but because of the physics of wavelengths and antennas, it needs a relatively huge aperture to achieve good angular resolution. SAR technique create a virtual or synthetic antenna by imaging coherently over a path that draws out the synthetic aperture. Of course, time continues as the the platform (satellite in this case) is moving. SAR then requires precise spatial/temporal awareness to combine the returns from the ground into a coherent image. It is similar to long exposure in photography leading to seeing dim objects far away. In both cases, if objects in the imaged scene are moving during the scanning period, they become blurred in the final result.
- mNovak 6y agoThis reminds me of the Rockwell Retro Encabulator https://www.youtube.com/watch?v=RXJKdh1KZ0w&t=1s https://www.youtube.com/watch?v=RXJKdh1KZ0w&t=1s
- jimmytidey 6y agoThe Rockwell encabulator would only be relevant if the SAR had parasitic side band resonance. Unlikely, IMHO.
- totetsu 6y agooh dear, I slack off from watching 5G training and get this..
- briandear 6y agoMaybe they should define “SAR” as well, given that anyone who has misconceptions might not even know what the hell they are talking about.
- ravi-delia 6y agoI find it incredibly endearing. Obviously it's not ideal in terms of public communication, but there's something wonderfully earnest about the way a lot of domain experts just kind of forget that most people don't share their obsession, let alone their knowledge.
- andi999 6y agoIt could also be smokescreen and mirrors. If you find the truth uncomfortable just hide it beneath technical mumble jumble.
- jhrmnn 6y agoIt could, but it isn’t in this case.
- andi999 6y agoWell then give me a real reason why it should not be possible. (Basically what they only say is why the appearance of penetrating building cannot be interpreted so easily)
- ravi-delia 6y agoAll of the assurance was in the first third at best, and the rest was explaining why it looks like it can penetrate buildings.
- andi999 6y agoYes, they claim the 'laws of physics' prevent that. They should specify which law exactly. Maybe too low SNR? I know for a fact you can use radar to see through walls.
- system123 6y agoradar is a technique, not a specific thing. Their radar is based in the X-band (9.5 GHz) which is known not to have the ability to penetrate much. In fact, while C-band SAR (Sentinel 1) can partially penetrate forest canopies, and the top few cm of soil, X-band waves can hardly do this and basically just provide a surface scattering.
- jcims 6y agoThe sad thing is they could do it with an animation pretty easily, it’s just not that easy to do animations.