GPS: What's it? How Actually it Works?

GPS: What's it? How Actually it Works?

The Global Positioning System (GPS) is a space-based satellite navigation, which provides location, time information, weather reports and etc., anywhere on or near the earth. This system was originally created by the United States for military purposes, and later it was opened to civilians, who can access the system freely with a GPS receiver. The GPS program provides critical capabilities to military, civil and commercial users around the world. In addition, GPS is the backbone for modernizing the global air traffic system.

  

At least 24 GPS satellites are always in orbit around the Earth, and they’re constantly broadcasting data. The GPS project was developed in 1973 to overcome the limitations of previous navigation systems, integrating ideas from several predecessors, including a number of classified engineering design studies from the 1960s. GPS was created and realized by the U.S. Department of Defense (DoD) and was originally designed and run with 24 satellites. It became fully operational in 1994.

The satellites are arranged in orbit and four satellites are visible in the sky from any point on earth by a direct path of radio transmission. If the transmission signals are being blocked then GPS system wouldn't be functioning. The system, also, wouldn't working in a cave under a mountain or in an under ground bunker.

Nowadays, many of us using handheld devices, which use satellites to pinpoint our locations almost anywhere on the planet. But anyone ever wonder how GPS works? GPS enabled devices do not interact the satellites to transmit information; instead they only receive data, which being always transmitted from satellites. 

How GPS Determines the Location: The device that built-in GPS, for instance - a car navigation unit or a smartphone, acts only as a GPS receiver and they do not contact the satellites to determines its location; but observing the radio signals, which were being broadcast, from the satellites, all the times. So, a GPS receiver listens for signals from 4 (or more) satellites and the signals from the closer satellites will reach sooner while signals from the farther satellites will arrive later. The actual time difference is very small and could be detected by GPS receiver. The timings of signal broadcasted from the satellites and the timings of signal received on the GPS receiver are compared and estimated by the receiver for the relative distances between all the satellites. Using Trilateration, which is a process of geometry, the receiver can determining its location.

 

Alternatives to GPS: Other alternate services, for GPS, are the cell phone towers in which the towers working in the way of measuring the signal strengths between multiple towers, then the GPS receiver could be estimating the current location. Through Wi-Fi enabled devices, it could also be determined the current location. The smart phone scans the nearby wireless networks, then sending the list of wireless network names with signal strengths to Google's servers. Google uses these database then estimates the location.

Devices could also be using Wi-Fi based positioning system (WPS), where GPS is inadequate due to various causes including multipath and signal blockage. Using WPS, the device is determining its current location, capturing street views (of Google), Traffics and nearby access points such as Restaurants, Petrol Stations, ATM Centers etc., for certain locations. Google wouldn't be the only provider for WPS, but it's most familiar to us. So, WPS is convenient, especially for the indoor locations, where GPS signals couldn't reach.

In addition, GPS could be restricted or shut down during the time of war or conflict; so, every nation needs their own satellites. Russia has its own GLONASS (Global Navigation Satellite System), European Union's Galileo Positioning System, China's Compass Navigation System, and India's Indian Regional Navigational Satellite System are their own, self sufficient satellite systems.