As well as everybody now wants a precise time, a lot of people also want to know their position as precisely as possible.
That's why humans created powerful navigation systems to achieve this goal : GPS, which is the most known, the Russian GLONASS, and soon the european jewel Galileo.

A navigation system basically give you :

But if these systems are nowadays largely used, only a few people actually know how these systems work, what are their caracteristics, their limitations, their differences, and their applications.

That's why we are 3 professionals here today.
First, my colleague .... will introduce you NAVSTAR (Navigation System with Time and Ranging), which is the official name for GPS, created in 1973 by the American Department of Defense.

Overview of the NAVSTAR galaxy: