5 ms·

Why does it seem that press releases and public statements like this tend to overstate things, to the point of fallacy, in order to make a definitive point? If

by jcims 6y ago

Why does it seem that press releases and public statements like this tend to overstate things, to the point of fallacy, in order to make a definitive point? If you took a SAR image of my home you would absolutely see how many vehicles are in my garage. Some examples from Sandia labs SAR image gallery - https://www.sandia.gov/radar/imagery/index.html https://www.sandia.gov/radar/imagery/index.html (I believe these are aerial vs. orbital but the technology is the same) Ku band SAR Airport Historical Site - Can see parked vehicles right through the roof of the building on the left - https://www.sandia.gov/radar/_assets/images/gallery/ku-band-5.png https://www.sandia.gov/radar/_assets/images/gallery/ku-band-... Ka band SAR Golf Course - Can see right through the roof of the clubhouse and golfers (eg. human bodies) on the greens - https://www.sandia.gov/radar/_assets/images/gallery/ka-band-3.png https://www.sandia.gov/radar/_assets/images/gallery/ka-band-...

StavrosK 6y ago
I don't understand what you think is shown "through" the roof of the clubhouse (or cars, for that matter). That's just the roof: https://goo.gl/maps/bsSQjADvWuynPLvq6 https://goo.gl/maps/bsSQjADvWuynPLvq6
- Firerouge 6y ago
  Interestingly it does seem to see right through the awning that's to the right of the roof. There appears to be a couple tables that are hiden from Google's satellite view but clearly visible to the bottom right of the building in the ka band SAR image.
  - StavrosK 6y ago
    The SAR photo was probably taken before an awning was installed.
    - Firerouge 6y ago
      I thought that might of been the case as well, but based on Google Earth Pro's historic satellite data, it's been there since 2009.
      - technick 6y ago
        How long has this witchcraft been around?
      - StavrosK 6y ago
        That's odd, but you can see in the SAR photo that there isn't even an outline of the awning, nor the golf carts under it, nor the columns that hold the awning up, but there are trees which aren't there in the photos from the ground.
        Firerouge 6y ago
        It certainly looks like you're right. While I can't find the image online earlier than 2010, there's an ieee research paper titled TanDEM-X for High-Resolution SAR Interferometry from 2007, so it certainly could predate the awning.
- jcims 6y ago
  I just started to doubt myself but you saved me lol. OK take a look at the front of that building (found on flickr) https://i.imgur.com/cDF8Fsr.jpg https://i.imgur.com/cDF8Fsr.jpg Now take a look at this map image, and go back and forth to see if you feel that the X i marked is a reasonable approximation of the photographer's location https://i.imgur.com/fvj0ZPj.jpg https://i.imgur.com/fvj0ZPj.jpg Now take a look again at the SAR image and tell me if you can see any artifacts from the front of the building through the roof (hint, zoom in and look for the curved line of bright dots :) ) https://www.sandia.gov/radar/_assets/images/gallery/ka-band-3.png https://www.sandia.gov/radar/_assets/images/gallery/ka-band-...
  - StavrosK 6y ago
    Not really, the building windows are octagonal (you can see that they're straight) and the dots curve. The brick wall at the front, though, has the exact same curvature as the dots, dead-on.
  - CapriciousCptl 6y ago
    I don't follow. Can you edit the ka band image and circle what you're seeing?
    - jcims 6y ago
      This part - https://i.imgur.com/CmtzOES.png https://i.imgur.com/CmtzOES.png But now that I have a better understanding of the layover effect I think it might just be that the satellite is looking from where it looks like the sun is shining, and it's directly imaging that front window frame and brick wall. Need our SAR pro to comment :)
enriquto 6y ago
I don't think that you are interpreting these images correctly (but the screenshots do not indicate the viewing direction, so it's not your fault). The objects that you see "through the roof" may be in front of the building, not inside. Radar imaging is based on the return time of a chirp to the antenna. If two objects appear on the same pixel in the image it means that they are at the same distance to the antenna. For example, if the sensor is at a (common) elevation of 45 degrees, a 10m vertical wall will seem to cover the 10m of ground next to it, and any object there will be superimposed with the roof of the building. EDIT: I have some professional experience with the interpretation of satellite SAR imagery.
- jcims 6y ago
  You're right I probably blew it with that one. I found the building on google maps and there's no cars there. BUT! What do you think about this one? - https://news.ycombinator.com/item?id=25482504 https://news.ycombinator.com/item?id=25482504
- rmrfstar 6y ago
  They should open up a rate-limited retail API that lets us verify for ourselves what is visible in our life and what is not. Otherwise we have to outsource our thinking to others who may have a conflict of interest.
  - jcims 6y ago
    I like this idea. There's already sales channels for this, they would just be another imaging provider.
  - notahacker 6y ago
    Many high value commercial applications of ultra high resolution SAR only involve small areas of land and irregular periods Ultimately satellite providers don't have any more obligation to subsidise access to their services to people wishing to verify for themselves that the product doesn't contradict the laws of physics than 5G providers or microchip providers.
Technically 6y ago
You can make the same claim about your own post: "seeing" is a very misleading description of the phenomenon you're describing.
jcrawfordor 6y ago
I have the local knowledge to tell you that there aren't parked vehicles in or near that part of the building. You can even see in aerials that it's that it's a lawn with walking paths and a prefab outbuilding. I think this SAR image may be from before the outbuilding was there, and historical imagery shows that it used to just be an extension of the lawn. I think the bright objects are a distorted reflection from elements of the building facade, perhaps. I don't know, I'm squinting at the SAR image having a hard time deciding if it depicts the outbuilding or not, and it perhaps says something about the limitations of SAR images that it's not clear to the untrained eye whether or not an entire building is there. I think it's possible the building is there and is just made of materials with very low reflectivity, there are sort of "ghost lines" that seem in the right place for its edges.
- jcims 6y ago
  You're right. Here's the back of the building - https://i.imgur.com/JRcer7d.jpg https://i.imgur.com/JRcer7d.jpg Why am I worried about SAR when Google is ten times creepier, lol. Could definitely be some kind of artifact
studius 6y ago
> Why does it seem that press releases and public statements like this tend to overstate things, to the point of fallacy, in order to make a definitive point? While in my mind, things were better with Fairness Doctrine and Equal-time Rule restrictions, I think we could solve this in the US by greater tax-funded federal, state, and local government-funded media, where the government has no control over that media aside from that of regulation to promote fair and equal representation within that media. Basically, put PBS, state, and local programming into a streamed source similar to Netflix/Hulu/Prime, produce content with quality surpassing other streaming services, and give the public air time both via meritocratic decision by randomly selected electorate as well as via lottery and availability. The BBC might be a good model to emulate also. At that point, there would at least be an alternative to B.S. journalism and bad media behavior reinforced by viewership and advertising dollars.
nitrogen 6y ago
There's that old video of a police helicopter tracking someone who shined (shone?) ^W^W pointed a green laser pointer at them, even through buildings. Was that SAR?
craftinator 6y ago
Look into the physics of how this technology works. If you do that, and take the time to grok it, you'll have the information to understand that this type of radar cannot penetrate any of the materials that buildings are made.
- andi999 6y ago
  10 Ghz is used in ground and wall penetrating radar
  - jcims 6y ago
    That's the disconnect here I think. SAR is a technique for building up a two dimensional image by rasterizing one dimensional signal reflection data. Any type of radiant energy would presumably support SAR techniques, from sonar to x rays, although the 'R' in SAR presumably limits it to radio frequency range (~30Hz-300GHz). Some of which, as I mentioned originally, absolutely would see through buildings. My point is that the headline and article are trying to make the case that 'SAR can't see through buildings', when it should be 'Why it looks like our satellites are seeing through buildings' because that is all that is explained.
    - andi999 6y ago
      Yes. And actually I wouldnt be surprised if their satellites actually can see through buildings (because the frequency band they use should allow that). Maybe just need to adjust the color-scale (or switch to logarithmic if it is not). I mean 10GHz SAR is capable: https://www.kurzweilai.net/seeing-through-walls-in-real-time https://www.kurzweilai.net/seeing-through-walls-in-real-time (of course SNR might be too low for satellite, but this is nowhere written)
derstander 6y ago
> If you took a SAR image of my home you would absolutely see how many vehicles are in my garage. Unless your garage was made of materials that are transparent to the frequency band of the radar or the collection geometry enabled the radar to image through a door or large windows, this is not true.

by jcims 6y ago

StavrosK 6y ago

I don't understand what you think is shown "through" the roof of the clubhouse (or cars, for that matter). That's just the roof: https://goo.gl/maps/bsSQjADvWuynPLvq6 https://goo.gl/maps/bsSQjADvWuynPLvq6

Firerouge 6y ago
Interestingly it does seem to see right through the awning that's to the right of the roof. There appears to be a couple tables that are hiden from Google's satellite view but clearly visible to the bottom right of the building in the ka band SAR image.
- StavrosK 6y ago
  The SAR photo was probably taken before an awning was installed.
  - Firerouge 6y ago
    I thought that might of been the case as well, but based on Google Earth Pro's historic satellite data, it's been there since 2009.
    - technick 6y ago
      How long has this witchcraft been around?
    - StavrosK 6y ago
      That's odd, but you can see in the SAR photo that there isn't even an outline of the awning, nor the golf carts under it, nor the columns that hold the awning up, but there are trees which aren't there in the photos from the ground.
      - Firerouge 6y ago
        It certainly looks like you're right. While I can't find the image online earlier than 2010, there's an ieee research paper titled TanDEM-X for High-Resolution SAR Interferometry from 2007, so it certainly could predate the awning.
jcims 6y ago
I just started to doubt myself but you saved me lol. OK take a look at the front of that building (found on flickr) https://i.imgur.com/cDF8Fsr.jpg https://i.imgur.com/cDF8Fsr.jpg Now take a look at this map image, and go back and forth to see if you feel that the X i marked is a reasonable approximation of the photographer's location https://i.imgur.com/fvj0ZPj.jpg https://i.imgur.com/fvj0ZPj.jpg Now take a look again at the SAR image and tell me if you can see any artifacts from the front of the building through the roof (hint, zoom in and look for the curved line of bright dots :) ) https://www.sandia.gov/radar/_assets/images/gallery/ka-band-3.png https://www.sandia.gov/radar/_assets/images/gallery/ka-band-...
- StavrosK 6y ago
  Not really, the building windows are octagonal (you can see that they're straight) and the dots curve. The brick wall at the front, though, has the exact same curvature as the dots, dead-on.
- CapriciousCptl 6y ago
  I don't follow. Can you edit the ka band image and circle what you're seeing?
  - jcims 6y ago
    This part - https://i.imgur.com/CmtzOES.png https://i.imgur.com/CmtzOES.png But now that I have a better understanding of the layover effect I think it might just be that the satellite is looking from where it looks like the sun is shining, and it's directly imaging that front window frame and brick wall. Need our SAR pro to comment :)

enriquto 6y ago

I don't think that you are interpreting these images correctly (but the screenshots do not indicate the viewing direction, so it's not your fault). The objects that you see "through the roof" may be in front of the building, not inside. Radar imaging is based on the return time of a chirp to the antenna. If two objects appear on the same pixel in the image it means that they are at the same distance to the antenna. For example, if the sensor is at a (common) elevation of 45 degrees, a 10m vertical wall will seem to cover the 10m of ground next to it, and any object there will be superimposed with the roof of the building. EDIT: I have some professional experience with the interpretation of satellite SAR imagery.

jcims 6y ago
You're right I probably blew it with that one. I found the building on google maps and there's no cars there. BUT! What do you think about this one? - https://news.ycombinator.com/item?id=25482504 https://news.ycombinator.com/item?id=25482504
rmrfstar 6y ago
They should open up a rate-limited retail API that lets us verify for ourselves what is visible in our life and what is not. Otherwise we have to outsource our thinking to others who may have a conflict of interest.
- jcims 6y ago
  I like this idea. There's already sales channels for this, they would just be another imaging provider.
- notahacker 6y ago
  Many high value commercial applications of ultra high resolution SAR only involve small areas of land and irregular periods Ultimately satellite providers don't have any more obligation to subsidise access to their services to people wishing to verify for themselves that the product doesn't contradict the laws of physics than 5G providers or microchip providers.

Technically 6y ago

You can make the same claim about your own post: "seeing" is a very misleading description of the phenomenon you're describing.

jcrawfordor 6y ago

I have the local knowledge to tell you that there aren't parked vehicles in or near that part of the building. You can even see in aerials that it's that it's a lawn with walking paths and a prefab outbuilding. I think this SAR image may be from before the outbuilding was there, and historical imagery shows that it used to just be an extension of the lawn. I think the bright objects are a distorted reflection from elements of the building facade, perhaps. I don't know, I'm squinting at the SAR image having a hard time deciding if it depicts the outbuilding or not, and it perhaps says something about the limitations of SAR images that it's not clear to the untrained eye whether or not an entire building is there. I think it's possible the building is there and is just made of materials with very low reflectivity, there are sort of "ghost lines" that seem in the right place for its edges.

jcims 6y ago
You're right. Here's the back of the building - https://i.imgur.com/JRcer7d.jpg https://i.imgur.com/JRcer7d.jpg Why am I worried about SAR when Google is ten times creepier, lol. Could definitely be some kind of artifact

studius 6y ago

> Why does it seem that press releases and public statements like this tend to overstate things, to the point of fallacy, in order to make a definitive point? While in my mind, things were better with Fairness Doctrine and Equal-time Rule restrictions, I think we could solve this in the US by greater tax-funded federal, state, and local government-funded media, where the government has no control over that media aside from that of regulation to promote fair and equal representation within that media. Basically, put PBS, state, and local programming into a streamed source similar to Netflix/Hulu/Prime, produce content with quality surpassing other streaming services, and give the public air time both via meritocratic decision by randomly selected electorate as well as via lottery and availability. The BBC might be a good model to emulate also. At that point, there would at least be an alternative to B.S. journalism and bad media behavior reinforced by viewership and advertising dollars.

nitrogen 6y ago

There's that old video of a police helicopter tracking someone who shined (shone?) ^W^W pointed a green laser pointer at them, even through buildings. Was that SAR?

craftinator 6y ago

Look into the physics of how this technology works. If you do that, and take the time to grok it, you'll have the information to understand that this type of radar cannot penetrate any of the materials that buildings are made.

andi999 6y ago
10 Ghz is used in ground and wall penetrating radar
- jcims 6y ago
  That's the disconnect here I think. SAR is a technique for building up a two dimensional image by rasterizing one dimensional signal reflection data. Any type of radiant energy would presumably support SAR techniques, from sonar to x rays, although the 'R' in SAR presumably limits it to radio frequency range (~30Hz-300GHz). Some of which, as I mentioned originally, absolutely would see through buildings. My point is that the headline and article are trying to make the case that 'SAR can't see through buildings', when it should be 'Why it looks like our satellites are seeing through buildings' because that is all that is explained.
  - andi999 6y ago
    Yes. And actually I wouldnt be surprised if their satellites actually can see through buildings (because the frequency band they use should allow that). Maybe just need to adjust the color-scale (or switch to logarithmic if it is not). I mean 10GHz SAR is capable: https://www.kurzweilai.net/seeing-through-walls-in-real-time https://www.kurzweilai.net/seeing-through-walls-in-real-time (of course SNR might be too low for satellite, but this is nowhere written)

derstander 6y ago

> If you took a SAR image of my home you would absolutely see how many vehicles are in my garage. Unless your garage was made of materials that are transparent to the frequency band of the radar or the collection geometry enabled the radar to image through a door or large windows, this is not true.