GPS (Global Positioning System)

In brief it is a global system, a system which locates anything on earth in terms of its co-ordinates i.e. altitude, longitude and latitude. To achieve this, there is a satellite network, control station network and receivers, which will receive the data from the satellites and let you, know on some form of display where you are. One can connect the receiver to computer and get your location on a map background or whatever modification one wants.

Introduction:
The concept of the Global Positioning System evolved in early days of 80’s. It was proposed for a worldwide navigation system to locate the objects or the roots and related purpose. This was the concept by US military. Although it was developed for the military, it was seen that it would be very much useful to civilians also. Advancements in field of electronics also helped the thing a lot to bring the prices down of the devices required in it. Before that it was for military only, which can afford such a costly affair. Due these reasons it helped a lot to make the system open for the entire rest world. GPS is relatively much better than other systems and it is on its way to becoming the primary means of navigation in most applications.

How our position is decided by using this system can be better explained thinking an example, which will be requiring a little bit knowledge of geometry.

Imagine you are at a location about which you are not at all aware of. If somebody tells you that you are 15km apart from a village ‘A’. Then you can think yourself on a circle of radius 15km from the village ‘A’ as center point. Now further you got known that you are 20km apart from village ‘B’. So now it is easier for you that you can say you on one of the two points, which are the intersecting points of the two circles of radius 15km and 20km. If you more get knowledge that you are 30k away from third village say ‘C’, then it’s pretty easy to say on which point you are. That will be the unique point of intersection of the three circles.

Yes, the same logic is applied in this system. Here you are told that you are this much distance away from a satellite, and all the satellites to which the receiver can view tell the same. So as in the example we needed 3 tellers to locate in a 2D environment, here you need 4 tellers (satellites) to tell your location in a 3D environment. Remaining is the part of the calculation and displaying it, which a receiver does.

Coming to actual system, it can be better viewed in the following segments or parts, which views the GPS System as whole:

1. Space Segment
2. Control Segment
3. User Segment

We will discuss each segment in little detail here........

Space Segment:
It consists of a satellite network, which in turn consists of 27 satellites. Only 24 of them are sufficient for the complete operation of the system, but the remaining three are for backup purpose i.e. whenever any of the 24 satellites is out of operation due to some or other reason then from these three, any one at appropriate location is brought in the operation.

The US Defense keeps the satellites in the orbit. They are approximately 11,000 miles above the earth surface. They travel at a speed of around 7,000 miles per hour.

They transmit signals consisting of the coordinate information, which is then received by the receivers and decoded to show the coordinates.

Control Segment:
Control Segment consists of tracking mechanisms to control the motion of the GPS Satellites and provide the necessary corrective action for their motion. It mainly has the satellite tracking Radars to get the position of the satellites and the wireless network to provide the corrective communication signals.
There are five control stations around the world, which controls and sets the satellites in the proper motion and direction. One of them is called master control station, and the rest are not named. The rest four collects the data from the satellites continuously and send the same to the master control station. The master control station corrects the received signals and then with the help of wireless communication network send back to the satellites.

User Segment:
The actual part with which the user actually deals the receiver. It is hand-held equipment, which has a display section, which shows the longitude, latitude and altitude of itself in turn of the person who is having it. It may have additional facilities which may include speed display, map display, etc.

So this is all about the introduction of the world famous GPS System.

The uses of the system depend on the occasion to occasion, may be as driver, sailor, pilots, hikers, and most important, military. The system is there and will remain but to make the efficient use of the system is up to the user.