And that, ladies and gentlemen, is how it is done.

"Nasa engineers say they are thrilled at just how well the Curiosity rover landing system worked when it touched down on Mars."  Story over at the BBC.
Figure shows the expected error ellipses for several other Mars landers, along with actual positions within their ellipses:

The landing sites are, of course, actually spread out over Mars, not all in Gale Crater as depicted in the above error ellipse diagram.  The lower figure shows their actual positions: