When I was a kid, I thought it was pretty cool that Maxwell Smart had a phone in his shoe. That’s old hat these days, but researchers have now developed more advanced podiatric technology: the shoe radar. And, yes, there’s a practical reason for it.
Why would you put a radar in your shoe? To keep from getting lost.
People rely on GPS devices to make sure they don’t get lost. But GPS devices rely on satellite connections, which are not always available. For example, a GPS device won’t do you any good if you’re exploring a cave, because it can’t receive a satellite signal underground.
But you can track your movements using an inertial measurement unit (IMU), which effectively tracks your acceleration to determine how far (and how quickly) you’ve moved. So, if you’re in the cave you could use your IMU to retrace your steps and avoid getting lost. Alas, IMUs have a flaw: they accumulate minor errors. If the IMU thinks you’re moving (even a couple of inches per second) when you’re actually standing still, within minutes it will misrepresent your position by over a dozen yards. That would be bad news if you’re lost in a cave.
Here’s where the shoe radar comes in. The radar tracks the distance between your shoe and the ground. If that distance doesn’t change, a navigation computer knows that your velocity is zero. The same navigation computer receives input from the IMU, and by “re-setting” your velocity to zero when you are standing still, eliminates much of the accumulated error from the IMU. In short, it gives you a much better idea of where you actually are. Pretty handy for you spelunking enthusiasts.
But its utility is not limited to cave explorers. GPS devices often lose their signals indoors, in cities with towering skyscrapers, etc., making the shoe radar pretty handy for urban pedestrians as well.
A paper describing the research, performed by a team from NC State and Carnegie Mellon, was published in IEEE Transactions On Microwave Theory And Techniques.
PS: I tried to find a clever way to incorporate Radar Love into the post, and could not. Here it is anyway.