GPS is free - but why US Military made it free for all?
GPS stands for The Global Positioning System, is a satellite-based radio navigation system owned by the United States government and operated by the United States Air Force. It's a global navigation satellite system that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. The GPS project was launched by the U.S. Department of Defense in 1973 for use by the United States military and became fully operational in 1995. The GPS provides critical positioning capabilities to military, civil, and commercial users around the world.
And it was allowed for civilian use in the 1980s. The GPS does not require the user to transmit any data, and it operates independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the GPS positioning information.
The United States government created the system, maintains it, and makes it freely accessible to anyone with a GPS receiver.
But the question is - Why it is free for civilian use and why US Military made it free for all?
In 1983, during the Cold War, a Korean Air Lines Flight 007 got a bit lost on a flight from New York to Seoul and strayed into Russian Airspace, and was shot down by the Soviets, there were more than 250 casualties.
As a result, President Reagan announced that GPS (which previously was only accessible to the military due to encryption on the satellites), would become available to all civilians, in order to stop this from happening again.
But, it's not fully free, technically speaking a tiny part of it is free. GPS, in fact, provides a dual-use system. It provides separate services for civil and US military users. These are called the Standard Positioning Service (SPS) and the Precise Positioning Service (PPS). The SPS is designated for the civil community, whereas the PPS is intended for U.S. authorized military and select government agency users. Access to the GPS PPS is controlled through cryptography. Thus PPS part of GPS is not open/free.
Though, the US Military still reserves the right to temporarily disable GPS for non-military use in certain areas. Note that if you were to try and build your own GPS jammer, you would probably be arrested. It's illegal.
GPS uses CDMA (Code Division) for Transmission of all satellite signal in a single frequency band. For this, there is a C/A-Code which is not encrypted and free to use for all nations. and within the same signal band their Lies P-Code which only US Govt can use because it is encrypted.
They can stop GPS anywhere and restrict any country from using it. Because of that, many countries have developed their own constellations of GPS satellites, and stopping by countries like the US will have no effect. Now, India, Russia, China, Japan all have their own GPS satellite constellations.
How does GPS work?
GPS work on Atomic Clocks and predictable positions of satellites and speeds of radio waves, identities the point of sending the signals in latitudes and longitudes so accurately, that it’s only a few inches scrambles, not more that.
The application of GPS is such that it is vital today in both the personal and business front.
Today, it presents an opportunity for young industries to diversify their applications at a faster rate. GPS is being actively used in smartphones, laptops, and tablets to make life easier for every individual. It is even used by logistic businesses and courier management services to increase efficiency and speed of delivery. Individuals who love to travel can use GPS get lost anywhere in the world to navigate their way back to familiar territory. It helps to point you towards the street with the least traffic every time.
In 2000, President Bill Clinton signed a bill to stop the scrambling - presumably because the advantage had become outdated - therefore making the system much more accurate for everyone. The free, accurate GPS that resulted made all sorts of things, most notably the modern smartphone and its mapping apps, possible.
When selective availability was lifted in 2000, GPS had about 5-meter accuracy. The latest stage of accuracy enhancement uses the L5 band and is now fully deployed. GPS receivers released in 2018 that use the L5 band can have much higher accuracy, pinpointing to within 30 centimeters, or just under one foot.