Nothing to do with AVRs, but can someone explain to me how the handheld ultrasound scanners detect position/motion? The ones they use on pregnant women, or old farts like me, when checking for Abnormal Aortic Aneurysm.
Do they have inertial sensors? Cameras like optical computer mice? Do they simply paste together images based on matching overlap, like dendrochronology? Or is there some other, blindingly obvious method that I've missed?