JAPAN'S PLAN for centimeter-resolution GPS location/navigation.

My first job -- while I was still in college in the early 1960's -- was to work on the initial attempts at satellite-based location. Location, not navigation. We were thrilled that after years of data collection we were finally able to distinguish two stationary antennas at the opposite ends of a 300-foot long building. Today, only 50 years later, we can tell whether a moving antenna (e.g., car) is driving on the wrong side of a 20-foot wide highway.

Note: if you bother to read the comments, they are mostly wrong.