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Global positioning allows tourists to navigate in the foreign country, in a tourist trip or even in a deep cave. But sometimes GPS-equipment fails, and the GPS signal is lost. Often this is because the GPS-receiver does not catch the signal from the satellite. Thus, developers had a task: to create an additional device which would locate the user in real time.
Researchers from Carnegie Mellon University and North Carolina State University have invented a sensor that helps to navigate in unfamiliar locality with a loss of GPS signal. The new device brought together a technology of measuring distance and velocity with a portable radar, making it possible to establish a point of finding the user. Novelty represents the inertial measurement unit, which is based on microelectromechanical systems with gyroscopes and accelerometers. Thus, tourists are able to monitor their own speed of movement, as well as they can learn what distance they have passed.
When using an inertial sensor, together with GPS devices, even in case of loss of satellite signal, you can almost freely navigate in an unfamiliar locality.
However, there is one drawback of an inertial equipment: it can record the movement of tourists at a speed of 0.1 m/s even if they will don't go anywhere. It would seem a trifle, but after a few minutes, the device indicates that a user has moved 20 meters. The developers have decided this issue by using a portable radar equipment and modular components, fixed to the shoe.
The principle of operation of the system lies in the fact that the radar is connected to a mini computer, designed by certain time intervals to measure the distance from the heel to the ground. If the distance is unchanged, the system "understands" that the user is stationary and throws the inertial velocity.