Replying to Avatar jamw

My understanding of this is that satellite and even airborne based SAR systems can only resolve objects of 25cm in size - i.e. at best, spatial resolutions for images of objects 25cm in size can be resolved. Still impressive but this limitation is due to the synthetic aperture size, which would need to be impossibly large in order to achieve mm-level spatial resolutions. However, InSAR (SAR Interferometry systems) can detect mm-level displacements (ground movement, landslides, tectonic shifts, etc) in the vertical or line-of-sight displacement plane), which is not the same as spatial resolution (for images). Fascinating stuff!
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mike 7mo ago

Yes, their accuracy is incredible, they can detect mm level change, but they are also rubbish because they can't detect 2 meter change 😂

Also, there are only a few of them, so you can't direct them where you want to observe something, you have to wait around 10 days until they cover the area you are interested in.

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jamw 7mo ago

Yep, the live satellite feeds one sees in the movies is not there yet. I think you can get hourly or so image updates and short-burst recorded video from some satellite systems though. But yes, only until they cover the area you want. They can’t be repositioned willy-nilly. 😁 I remember back in 1995 or so we had a visiting lecturer from one of the satellite imaging companies and the photos — dune advancement and vegetation growth/changes around the Sahara — he handed out back then were pretty impressive. Though I tried, he wouldn’t answer any questions about their in-development spatial resolutions 😅 - wish I could remember where he was working.