It’s understandable to think of the Internet of Things (IoT) as composed primarily of sensors that are fixed in place and continuously measure and report on temperature, motion, pressure, activity, and many other physical phenomena. The reality is that’s only a small part of a much bigger story.
Many IoT applications are mobile and implement on-the-go sensing, including imaging and specialized spectral sensing. Thus, precise knowledge of their orientation and location is needed for navigation, guidance, and data reporting. These include unmanned aerial vehicles (UAVs or drones), self-driving cars, autonomous submersible vehicles, industrial robots, surgical robots, trucks at mining sites, subterranean mine exploration and drilling, self-driving tractors, construction equipment, warehouse lifts and dollies…the resultant Internet of Moving Things (IoMT) comprises a very long list (Fig. 1).
1. Many IoT applications, such as aircraft control, military, and even farming, aren’t static but rather always on the move, leading to the Internet of Moving Things (IoMT) with requirements for high-accuracy position determination and navigation.
Why not just use GPS with its worldwide coverage (or European Galileo or Russian GLONASS satellite-based systems)? The answer is simple: GPS and the others alone won’t suffice, for multiple reasons. First, GPS doesn’t work indoors, underwater, or in areas “shaded” by overpasses, heavy tree cover, and barriers. Keep in mind that the received GPS signal level at the Earth’s surface is a minuscule −160 dBm. Second, GPS signals can also be overwhelmed by local interference, whether inadvertent from nearby EMI/RFI sources or noise-generating power systems, or deliberate jamming and spoofing.
Fortunately, there’s an alternative technical solution that has none of the unavoidable weaknesses of GPS: An inertial measurement unit (IMU) that consists of a three-axis gyroscope to determine angular orientation, plus a three-axis accelerometer array to measure acceleration in each plane.
Unlike GPS, an IMU is just that—an inertial measurement system that requires no outside inputs or signals of any sort to assess acceleration and orientation. Its capabilities are based on fundamental principles of matter, mass, and physics, all of which are self-contained and immutable. In short, no external event can adversely affect an IMU (other than an intense electromagnetic pulse, of course).