Knowing your location in today's world is more and more essential and fundamental. Whether in the transport of goods and people, in the work of rescue services, but also in tourism and moving around the city, knowing the exact location brings not only a feeling of security and safety, but also economic profit or strategic advantage.
With the boom in miniaturization and the development of mobile phones, the GPS module is a common part of inexpensive devices, and positioning is a matter of seconds. But even in the modern world interwoven with the signal of global positioning satellites, it is surprisingly easy to "not be on the signal".
If the GSM provider's GSM signal is available, the situation is still quite rescued, but it is enough to be in a building with massive walls, underground (eg caves, subway) or in the middle of a rock town or remote mountain valley and any possibility of any network wireless signal is impossible.
AND THATS WHY INFA - Inertial for all - EXISTS! :)