To understand how images make it from satellites in orbit to Google Earth, you should take a look at Frank’s excellent about Google Earth imagery post from a few years ago. In short, Google doesn’t own any satellites that capture imagery; they buy the imagery from providers such as DigitalGlobe.
With that in mind, Richard Hollingham of the BBC took a trip to Ball Aerospace in Boulder, Colorado, where the WorldView-3 satellite is currently being assembled for DigitalGlobe.
WorldView-3 will be able to capture imagery at a remarkable resolution of just 25cm, though only the US government can purchase imagery that detailed. For Google Earth (and similar mapping projects, such as Bing Maps), the imagery will be released at a resolution of 50cm. As the article points out, from more than 600km away, travelling at around eight kilometres per second, capturing an image half-a-metre across is an impressive technical achievement, and is less likely to raise concerns about privacy.
It’s an excellent article that shows a bit more about how things work in regards to satellite imagery, and I recommend you check out the full story for yourself.