4 ms·

Can someone explain what the advantage of this is over a typical optical visible range satellite.

• _adamb 6y ago
  It can see through clouds and take pictures at night!
  • reasonabl_human 6y ago
    Yep, and depending on power and focusing, can ascertain better resolution and more clearly see object definition as opposed to blended colors
• pratyushc 6y ago
  I don't all the pros and cons, but SAR can see through cloud cover.
• shash 6y ago
  It can see through buildings, it can do some pretty precise depth estimates,... It’s not a replacement for visual range (or infrared for that matter) but an additional sensor. It’s usually used to create things like elevation maps. So all those altitude measurements that you see on Google Earth might be at least partially SAR.
  • K0balt 6y ago
    "it can see through buildings" Perhaps you missed the point of the article? While it is true that some implementations of SAR can image through walls at short distances (tens of meters), SAR is a very broad term and those systems are very different from the imaging systems in the article.
    • shash 6y ago
      OK, never comment from a mobile phone! Of course I meant it can't see through buildings!
• enriquto 6y ago
  Besides seeing through clouds and at night, you can often correlate images taken at different times and detect tiny movements (of fractions of a millimeter). This technique is called "interferometry". You can observe minute movements of large swaths of terrain; this is impossible with optical images.
  • notahacker 6y ago
    As a relevant commercial example, you can see patterns of subsidence which indicate a sinkhole is about to form near your mine. You're probably only looking at a relatively small area but it's unlikely to be evident from optical images. As an indication of how sensitive it is, you can use SAR interferometry to see where Crossrail tunnels have been bored under London, despite the elevation change of the buildings and roads on top being too small to have had any impact on their structural integrity. The caveat is that this level of sensitivity you get when looking at smooth, undisturbed surfaces like the roofs of buildings isn't matched when you're looking at fields with growth and soil movement
    • enriquto 6y ago
      > looking at smooth, undisturbed surfaces like the roofs of buildings a flat roof (with fine enough texture) will be reflective thus invisible. What you see are precisely tiny "corner" reflectors formed by large enough gravel, rocks and building structures. On a mountainous area, as long as you have some rocks and gravel here and there, you are still able to find correlations--and thus interferences. Of course, if all you have is wet mud and vegetation there's nothing to do, but this is not often the case. In a region of special interest like near a mine, people often install ad-hoc corner reflectors at calibrated positions.