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GPS definition
GPS, or Global Positioning System, is an onboard vehicle navigation device.
It usually uses a satellite navigation device to obtain its position data, which correlates to a position on the road, to provide the program direction to follow.
The two main forms of GPS navigation systems
The integrated units produced at the factory and the vehicle are included in the infotainment system.
In contrast, the portable units consist of autonomous GPS navigation devices and applications.
- GPS for smartphones (Google Maps or Via Michelin, for example).
- The main appeal of integrated units is that they don’t clutter the dashboard with extra gadgets, brackets, or power cables.
- And, because they are coupled to the vehicle’s infotainment system, they offer greater convenience (navigation, vehicle information controls, air conditioning, etc.).
- However, built-in units are a relatively expensive option, as are map updates, and are sometimes just as difficult to replace.
- Mobile GPS less expensive than integrated GPS
- And also,Mobile GPS navigation systems generally much less expensive than integrated units, especially smartphone applications (Google Maps and ViaMichelin are free).
- And also, they are easily transportable from one vehicle to another. The major drawback is additional bulk.
GPS members
The GPS Global Positioning System, like GLONASS, is of three sectors or components:
Space sector
It is made up of 24 satellites arranged in six orbits at the rate of 4 teams in each orbit.
The satellites orbit and the Earth at an altitude of 20,200 kilometers (below geostationary satellites).
And also, speed of rotation is one revolution of the Earth every 12 hours, following a route with an inclination of 55º for the celestial Equator and a difference of 90º of arc between the satellites.
To this add the wide coverage geostationary satellites of the WAAS / EGNO system.
Land sector
It deals with correcting the satellites’ signal and possible deviations from the orbit.
The land sector comprises 9 stations: 1 general, 5 tracks, and 3 data.
User sector
It is compose of an amplifier, antenna, and receiver.
The team is responsible for selecting the satellites that provide information to calculate the position and measure the time between transmissions.
The combination of the three sectors provides position and time with the global coverage.
It ensures that any user has between 6 and 8 satellites visible on the horizon at all times.
How GPS works?
Each of the orbiting satellites has four atomic clocks.
Atomic clocks are the most accurate that exist, having a delay of 1 second every three million years.
And is that time is essential to calculate the position.
And also, The GPS provides the position and height data.
For that, you need to have coverage of four satellites.
Three to calculate the situation and one more for the height.
Each of the satellites emits two signals.
One that acts as a matrix and another to correct the deviation of the ionosphere.
The user equipment measures the time it takes for the signal to travel from the satellite to the receiving antenna (known as the broadcast time), so both must be synchronized.
And also, the time multiplied by the speed of propagation of the waves (light) in the atmosphere, makes it possible to calculate each of the satellites’ distances.
In this way, it is known where each transmitter is and the distance to the user.
With these data, the position can be establish as the geometric place where the three spheres meet, with the center in each of the satellites and the calculate distance as a radius.
However, this position alter by the possible desynchronization between the transmitter and receiver clocks and atmospheric disturbances.
The DGPS is responsible for correcting it.
GPS accuracy
Degraded voluntarily by the American army until 2000, the GPS’s accuracy is today of a meter’s order but depends on the equipment uses and the number of satellites invisibility.
GPS receiver
The association of a GPS receiver and mapping software provides an efficient route guidance system, developed in different forms:
And also, onboard system in a car, autonomous unit with an integrated receiver, personal assistant, or smartphone associated with a GPS receiver.
