Harry Potter and the “Marauder’s Map”

The Harry Potter story has been read by millions and the Hogwarts universe of witchcraft and wizardry has become world famous. With the help of his two best friends, Hermione and Ron, and all kinds of magical creatures and objects, Harry takes on the dark Lord Voldemort and his followers who want to gain control of the world of witches and wizards. The “Marauder’s Map” is one of Harry’s best-known tools and first appeared in “Harry Potter and the Prisoner of Azkaban” (Warner Bros. Entertainment). All those touching the map with a wand while uttering the magic words “I solemnly swear that I am up to no good” will see the actual positions of everybody present in Hogwarts and the directions they are heading. Harry and his friends use the map, for example, to avoid meeting people they want to keep clear of when discovering hidden rooms or when sneaking out of the school grounds at night.

An essential part of the technology is the interaction between software and motion sensors which, in turn, could transfer the “Marauder’s Map” to our “Muggle World.” Wang explains: “Devices equipped with the technology can determine your position and then send it to a receiver whereby you are made visible on a digital map.” Real time movement can also be seen. The basic principle of the technology originally stems from seafaring where the so-called “dead reckoning“ has been applied for centuries now.

Whenever a ship’s position was known but navigation was made impossible by clouds or fog obscuring the starry sky, the sailors lowered a wooden board weighed down by lead that was attached to a line with a number of knots at uniform intervals. After a certain period of time, the line was reeled in and the speed was calculated by means of the number of knots that passed through the sailor’s hands within a given time. The direction was established using a compass. All the data was then combined with the speed and the sailors could determine where they were on the map.

This is where Bosch’s PDR system is particularly strong: To determine positions, it does not need continual Wi-Fi or GPS. As soon as the device establishes where it is situated, it carries out the additional positioning using a gyroscope and accelerometer. The Smart Sensor measures the movement of its wearer to localize itself. It is made possible by the algorithm developed by Bosch; it calculates the position using the direction in which one is running, the stride length, and the time taken. The minimal power consumption is another key advantage of the system: “As the positioning is no longer done by a global navigation satellite system alone but with the help of built-in motion sensors, the Smart Sensor uses up to 80 per cent less power than conventional GPS devices,” points out Wang. It conserves the battery and is therefore very useful, especially in devices with small batteries.