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In this specific article, we are going to learn about the working of GPS. In the upcoming articles, we will be dealing with the interfacing of of GPS module with the Arduino. I feel that it’s important to know the working of the module which we use in our project instead of just learning about ‘how to make the module throw it’s data values at us”…..
GPS stands for Global Positioning System and is mainly used to locate the exact location of the receiver with the help of data which it gives (out of which most important is Longitude and Latitude coordinates)
Working :
– The working of the GPS module is based on the communication between the satellites and the gps receiver module.
For locating the position of a place on earth, we need several parameters like Longitude and Latitude (2-D) and an extra Altitude (for
3-D)
– To locate the position, in GPS, we have something known as Trilateration.
In 2-D,
we need a total of 2 satellites (say S1 and S2 here). We are suppose located at point O and we need our location through GPS.
Fig. Determination of position in 2-D
– This implies that, O is somewhere on the region common to circle-1 and circle-2. This means it lies in the points of intersection of circle 1 & 2 (here O and P).
– To decide between O and P, we take into account the circle-3 which is the earth surface itself. All the 3 circles intersect at O (therefore, P is eliminated) and hence we obtain the position of a GPS receiver in 2-D.
In 3-D,
– We need a total of 3 satellites for locating position of GPS receiver
Here, we need to consider just the spheres instead of circle.
For quick overview,
But, there exists a problem of time delay, since the satellites have accurate atomic clocks while the GPS receivers uses the clocks which are installed in mobile phones.
But since all the satellites use the same specifications for atomic clock, the ‘time offset’ is the same. Even error of microseconds can give an error in kilometers !! Hence we use fourth satellite (S4).
As we discussed earlier, that we need the distance ‘d’ for locating the positions of satellites.
- But HOW DO WE EXACTLY DETERMINE ‘d’ ?
The ‘radio signal’ which is sent, it carries 2 information mainly :
– Exact time when it was transmitted (t1)
– Position of satellite
Now the receiver receives the signal at time t2 (say) :
The below is about What happens inside the GPS receiver (mainly a topic of discussion for our next Article)
Keep Learning !!
