【英语时差8,16】鞋子里的GPS

（单词翻译）

 But measuring movement is actually pretty tricky¹. Any small mistake in the measured acceleration² results in position errors that grow with time. So even if you’re standing³ still and just rocking in place, a navigation computer relying solely⁴ on the IMU readings may show you wandering off in a random⁵ direction. And that’s where radar⁶ comes in. Engineers have developed a tiny radar sensor⁷ and navigation computer that attach to a shoe to keep track of the space between the shoe’s heel and the ground. Basically, the radar system helps the IMU device more accurately⁸ sense when you’re moving and when you’ve stopped, which helps reduce navigation errors. None of this technology is available in your local shoe store yet. But someday it could find its way there.