The Global Positioning System (GPS) is a navigation and precise-positioning tool. Developed by the Department of Defense in 1973, GPS was originally designed to assist soldiers and military vehicles, planes, and ships in accurately determining their locations world-wide.

Today, the uses of GPS have extended to include both the commercial and scientific worlds. Commercially, GPS is used as a navigation and positioning tool in airplanes, boats, cars, and for almost all outdoor recreational activities such as hiking, fishing, and kayaking. In the scientific community, GPS plays an important role in the earth sciences.

Meteorologists use it for weather forecasting and global climate studies; and geologists can use it as a highly accurate method of surveying and in earthquake studies to measure tectonic motions during and in between earthquakes.

** GPS frequencies **

GPS units operate on a number of different "channels" or frequencies, some of which are under development and some of which are not used by "regular" GPS units. The principle operating frequency of the GPS system is 1575.42 MHz. That's 1.57542 GHz or 1,575,420,000 cycles per second.

** GPS bandwidth **

Bandwidth is the difference between the upper and lower frequencies in a contiguous set of frequencies. It is typically measured in hertz, and may sometimes refer to pass band bandwidth, sometimes to baseband bandwidth, depending on context.GPS carrier frequencies are in L band from 1227.6 MHz to 1575.42 MHz so the bandwidth will be upper frequency minus lower one so it comes out to be 347.82 MHz

** GPS blockers **

The GPS signal jammer works by sending out its own signal on the same frequency as the GPS unit, a noisy signal that prevents it from receiving or transmitting any useful information. There are a number of types of noise signals it can send; some call for a narrowband Gaussian signal, others for a simple continuous wave. There is variety of devices available in the market to block GPS locally. These are portable, handheld devices capable of jamming GPS signals leaving your receiver void of GPS signals.

If you are planning to buy some jamming device you must check the range of frequency it blocks also keep in mind that the jammer is local and does not disturb ambulances and other communication outside your premises.