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Comment by TomasD | Hacker News Reader

You can fly your satellites lower in mars due to atmosphere density, as low as 20km it appears

On top of that isn't the lower resolution on earth more for military reasons than a technical one or is this not the case any more?

Hasn't been really the case since french airbus started offering highres global imagery. If you have deep pockets, you can buy 30cm/px (i.e. order of magnitude better than this Mars dataset) images of pretty much anything.

I wonder if there's any sources for those images that aren't cough restricted. Could be interesting to play with, though maybe not worth paying for.

What do you mean, there are many resources that provide access to various satellite images. In general satellite imaging is not really that sort of hushhush industry it maybe was 50 years ago.

I read parent as looking for sources that provide access to hi-res satellite imaging, without them needing to provide access to their wallet.

I think the thread is referring to satellite pictures of more sensitive locations (like military bases, gov facilities, etc)

But I can imagine it all depends on jurisdiction. A Russian or Chinese satellite imagery company will have no problem publishing clear images of US military bases, while an American satellite company may have to comply with US laws prohibiting that.

And vice versa.

Ultimately if you cobble together imagery from multiple sources, you can probably get everything you want.

Well yes, but we certainly have better resolution imagery of Earth for many places. It's just that the Mars data is free and the Earth data is owned by corporations that sell access to it for a lot of money.

And presumably the atmospheric distortion is much less as well.

it's surface area also a lot smaller

However, the total surface area of Mars is roughly equal to the total land area of Earth.

If I wanted to make a textured globe, you just made my oceans totally smooth. Some of the tallest mountain ranges we have are in the area you just nulled out.

And how exactly would satellite imagery (no matter which wavelength range) help you texture the ocean floor in your globe?

nobody said optical wavelengths were the only meaning of imagery.

Turns out the surface of the ocean has ridges and valleys that match the seafloor, and these can be measured by radar from a satelite

Atmospheric distortion looking down is not as severe as it is looking up. This is because the distortion subtends much greater angles looking up than looking down, since the distortion is close to the observer. Looking down, it’s also true that, at least in daytime, exposures are very short as well by virtue of the earth being very bright.

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