The satellite positioning system is able to determine a person's location anywhere in the world, if only the receiver was in the area of ??the satellite. Inside the room this is more difficult. Engineers of the University of Utah have developed a device that determines the location with an accuracy of 5 meters without the aid of GPS. The navigation system is installed in hiking boots and helps rescuers and firefighters navigate inside buildings. Also, it can be integrated into video gaming equipment in virtual or augmented reality. The sensor is based on a gyrostabilizer - a box with a gyroscope, a magnetometer and an accelerometer. Such systems are installed on airplanes. Engineer Darrin Young decided to apply them as a portable electronics. But cheap versions of gyrostabilizers start to fail over time, and errors quickly accumulate. "If you sit still, the reading should be zero," says Young. But after 5 - 10 minutes of sitting on a chair a cheap device can begin to assert that you have moved a hundred steps. Engineers have found a way to calibrate the gyrostabilizer using biomechanics. During each step, the heel is pressed to the ground for about 100 milliseconds. This instant of rest can be measured and used to correct the readings of the device. Having developed a pressure sensor, the researchers placed it in the sole of the shoe and connected it with a gyrostabilizer. In total, the correct operation of the system requires about 1000 sensors (with a margin, in case several break down from the load).

In the prototype, the printed circuit board is installed outside the boot, but in the final product it will be hidden inside and connected via Bluetooth. During the tests, engineers walked through Salt Lake City for about three kilometers, and then compared the obtained prototype data with the GPS readings. After ten such walks, the maximum inaccuracy was 5.5 m, that is, it was on par with the GPS, but the new system worked with the same accuracy and inside the premises, reports IEEE Spectrum.

The sensor in the boot allows you to accurately determine the location without GPS.