Comment by cyberax

> I imagine that satelite imagery is a bit needs based but maybe every square meter of the earth is captured at least once a couple of months

Probably, but likely not as thoroughly as you'd think.

The problem with most high-resolution imaging satellites is that they are not designed to work over the ocean. They can't track the Earth perfectly, so they use a lot of image processing to "unsmear" the images. These algorithms rely on tracking recognizable features moving across the frames. Which obviously fails with the ocean.

So you often get hilarious results with images of offshore drilling platforms or ships.

That being said, there are satellites specifically designed for ocean observation, so they likely won't miss something as big as a new island.