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PhoneRadar Explains

What is GPS – How does it work, and what are its types?



GPS locking

GPS (Global Positioning System) is a satellite based navigation system, which assists in providing the location and time information. The system developed by the United States’ Department of Defense, uses between 24 and 32 Medium Earth Orbit satellite for the microwave signals for the precise information. The GPS provides the location and time information in any weather conditions, in any part of the world, for the entire day.

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How does the GPS work?

The GPS works with the receivers which would compute all the data provided by the satellites, and the computing is called “triangulation” where the position is found by using at least three satellites at once, and this is indicated in the longitude and latitude, and it is between 10 to 100 meters in accuracy. This is then used by the different applications and software for their own purposes, for example, providing directions to the users for a particular place.

With a least number of three satellites, the 2D position (longitude and latitude) of the GPS receiver is found, and if there are four or more satellites in view, the determination of the 3D position (with the addition of altitude) is found. Once all this is tracked and the GPS receiver is in sync with the satellites, the other information such as speed, distance and calculation of time to reach the destination are all the possible calculations.

GPS locking – is something what would make the positioning accurate. The GPS lock is dependent on the movement of the tracker. For example, if someone is driving, the accuracy is less and it takes more time than usual to find the exact location. The time needed for the GPS locking depends on the way a GPS receiver starts, which is of three types – Hot, Warm and Cold.


Hot Start – the GPS remembers its last calculated position and satellites, the almanac used and the UTC time. It then would attempt to lock onto the same satellites and assess the new position based on the information already available. The working of this depends on the position you are at. If the GPS receiver is around the same location where it was previously where the GPS was last turned off, then the tracking would be very fast.

Warm Start – in this, the GPS receiver would remember all the previous information except for the GPS satellites which were in view last time. Thus, a reset of the data is done, and the receiver attempts to get the satellite signals and get a new position. Although it looks for the satellites, the information about the satellites to look for is already there. It is slower than the Hot Start, but not the slowest one.

Cold Start – There is no known information, and thus the device tries to get all the information such as the GPS satellites, almanac and finally the position, thus making it the slowest way to lock the position.

Applications of GPS

The GPS was earlier used for the military purpose, but then it was released for the use by civilians, and since then, there have been multiple uses of the GPS.

The use of this is in Astronomy, Cartography, Automated Vehicles, Mobile phones, Fleet tracking, Geofencing, Geotagging, GPS Aircraft tracking, Disaster relief, Emergency services, Navigation of vehicles, Surveying, Robotics, Tectonics and in a lot more areas.

Types of GPS in mobile phone industry –

A-GPS (Assisted GPS) – this type of GPS is used to speed up the start-up time of the GPS based positioning systems. The A-GPS would assist the receiver in getting a lock when the signal is weak. For this to work, though, a network connection is required in the mobile phone because the A-GPS uses the assistance server to get the lock.

S-GPS (Simultaneous GPS) – it is a method to enhance the satellite-based reporting ability to a network carrier. The S-GPS allows a cell phone to receive both GPS and Voice Data at the same time, thus improving the sensitivity and allowing the network providers to give services based on the location.

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