![]() This system comprises International Systems such as GPS (US), GLONASS (Russia), Galileo (EU), BeiDou (China), IRNSS (India), and QZSS (Japan). The Global Navigation Satellite System (GNSS) is a combination of several Satellite position systems. ![]() The fourth satellite can also be used to move the position fix from 2-Dimensional, into a 3-Dimensional fix, giving an altitude value.Ī term quite often seen when looking at GPS devices is GNSS. Four satellite position fixes are much more accurate in comparison to three satellite fixes. A benefit of this is that GPS Receiver times are extremely accurate, meaning that once the time is ‘locked on’, it will not drift off the time fix. In the first approximated values from the three satellites the time offset/delay would be considered zero, however, the fourth satellite provides an extra distance measurement, which in turn allows a precise time offset to be calculated. Unfortunately, the satellites have high-precision atomic clocks, whilst the GPS receivers such as your mobile phone do not. Of course, for this to be achievable, the GPS Receiver needs to have an internal clock as a way of measuring time delay. The distance is calculated by measuring the time taken for the signal to arrive from the satellite by the GPS receiver using the following equation: Time delay of Signal * Speed of light = Distance Whilst only 3 satellites are required for a position fix, a fourth one is used to ‘validate’ data from the other three and improve accuracy. Doing this will create a point at which they all intersect, and this is how your location is determined. This process is repeated for the 2nd and 3rd satellite. The distance measured creates a sphere of equal distance in all directions. ![]() The distance from the satellite to the Receiver is measured, but the angle is not known (therefore trilateration is used). Satellite #1 will broadcast a signal that reaches the GPS Receiver. ![]() Trilateration works by using the three satellites and the GPS receiver to determine the distance from each satellite. This differs from triangulation, as trilateration only measures distance, not angles. The satellites are positioned and orbited in such a way, that there are always usually at least 6 satellites in view, although this is not achievable 100% of the time.Ī minimum of 3 Satellites is required to give a position fix, as the location is determined using Trilateration. Several different systems accumulate together to form GNSS which will be discussed later…!Ĭurrently consisting of multiple active orbital satellites, GPS is the most widely used satellite navigation system in the world, and in simple terms, GPS is a navigation system that consists of satellites, receivers, and complex calculations to determine location, speed (velocity), and time data. The GPS system is a satellite-based radio navigation system (RNSS) and is one of the Global Navigation Satellite Systems (GNSS). It is operated by the United States Space Force (USSF). The system was originally named Navstar GPS. GPS stands for Global Positioning System and is owned by the US Government. You’ve all heard it mentioned more times than you care to admit, but what exactly is GPS?
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