GPS consists of 3 segments: the Space segment, Control segment/controller, and User segment. Where the space segment consists of 24 satellites that operate in 6 orbits at an altitude of 20,200 km and inclination of 55 degrees over 12 hours (satellites will return to the same point in 12 hours). The satellite circles its orbit so that there are at least 6 satellites that can be monitored at any point on earth. The satellite sends position and time to users all over the world. With such a sophisticated capability, it’s no wonder why GPS isn’t being used only in the military anymore, and even other fields of work have begun to use GPS too. As an example, a lot of companies these days use GPS with geo fencing features in order to conduct location-based marketing.
Each one sends two signals, they are L1 with 575.42 MHz and L2 with 1227.60 MHz. L1 signal is modulated with two pseudo-random signals, P-code (Protected) and C / A (coarse / acquisition) code. L2 signals only carry P codes. Each satellite transmits a unique code so that the receiver (GPS device) can identify the signal from each satellite. When the “Anti-Spoofing” feature is activated, the P-code will be encrypted and then known as the P (Y) code or the Y code.
GPS devices specifically for civilians only accept C / A codes on L1 signals (although sophisticated GPS devices can utilize L2 signals to get more precise measurements).
GPS devices receive signals that are transmitted by GPS satellites.
In determining position, we need at least 3 satellites for positioning 2 dimensions (latitude and longitude) and 4 satellites for positioning 3 dimensions (latitude, longitude, and altitude).
The more satellites obtained, the higher our position accuracy will be. To get these signals, the GPS device must be in an open space. If our GPS device is in a room or dense canopy and our area is surrounded by tall buildings, the signal obtained will be reduced so it will be difficult to determine the exact position or even unable to determine the position.
Through GPS we can find out the existence of an object wherever the object is in the entire face of the earth both on land, sea, and air.