If somewhere your mobile phone is having difficulty in getting the correct location, don’t worry, just turn on the WiFi. Since the location data of most of the world’s WIFI is already present in Google’s servers, in this situation your phone’s GPS will your exact location based on the location of nearby WIFI.
The interesting thing is that you do not even need to “connect” WIFI. The work will be done just by turning on WIFI.
There are around 32+ satellites roaming 12,550 miles over your head, which runs GPS (Global Positioning System). You are under the “surveillance” of at least 4 satellites at any given time. These satellites emit radio waves towards the Earth, which your phone or device detects.
In this process, you can find out exact location by finding your distance from three satellites through a process called “trilateration” and the fourth satellite cross-checks that location. Through this GPS system, mobile phones can be detected with an accuracy of 5 meter difference and any advanced navigation device can be detected with an accuracy of 1 inch difference.
This GPS system originally was an American Defense System, which later on made available for general public with “Selective Availability”. American Government refused to provide GPS guidance to India during the 1999 Kargil War with Pakistan. Therefore, in 2006, India started its own navigation system called “NAVic” which has 7 satellites as on date. At present, “NAVic” is capable of providing surveillance not of the entire world, but of the 1500 km radius around India with a location accuracy of 3 meters.
Lets talk about GPS and Relativity if you are keen to deep dive.
Since the speed of a satellite in orbit is 4000 meters/second and the speed of a person on the Earth’s equator is approximately 465 meters/second (From the observer in space), the clock on the satellite becomes “slow” compared to the clock on Earth due to this speed difference. Now when both watches tell different time then there will be difference in location detection also with time.
It can also be said that due to this time dilation, there is a difference of 2.17 km in the GPS location “plus” in 24 hours. This happens under the principle of “Special Theory of Relativity”. Now, since the clock on the Earth is technically closer to the center of the Earth, i.e. “more mass”, hence under the principle of “General Relativity” this time the speed of the Earth’s clock becomes slower than the satellite’s clock, and in 24 hours there is a difference of “minus” 13.7 km per hour.
Now if you add these two differences, it becomes clear that if the clock present in the satellite is not set according to Einstein’s equation, then within a day the GPS will start giving your location wrong by a difference of 11.53 km.
In this way GPS itself confirms Einstein’s relativity.
