Question

Identify a technique(sensor) through which we can measure the speed of a train and its location. explain its working briefly?

Answer 1

We want to measure the speed of a train and its position using a sensor. The technique or the sensor best suited for this application is called the GPS sensor or the GPS technique. It gives accurate information about the train location and arrival times at different stations.

Working in Brief:

1) Small History:

The full form of GPS is the Global Positioning System and it was originally developed by the US mIlitary. Its been working fully as a global positioning and navigation system since 1995. It is a system comprising of a total of 32 satellites, of which 31 satellites are active.

It was first launched in the year of 1978 by the US Space Force and originally named as NAVSTAR GPS.

2)Working:

Though GPS consists of a total of 32 satellites they have different purposes. GPS sensors are receivers with antennas and they use a satellite-based navigation system with a network of 24 satellites in orbit around the earth to provide position, velocity, and timing information.

GPS consists of three segments - the satellite constellation, ground control network, and user equipment. These satellites are about 20,000km above the surface of the earth and orbit the earth twice a day; The orbits are nearly circular and equally spaced about the equator at a 60-degree separation with an inclination of 55 degrees relative to the equator. The satellites are placed in such a manner that from each place on the earth 6 satellites are always visible. To get an accurate result, 4 satellites must send and receive signals with the GPS sensors on the vehicle.

The GPS receiver gets a signal from each GPS satellite. The satellites transmit the exact time the signals are sent. By subtracting the time the signal was transmitted from the time it was received, the GPS can tell how far it is from each satellite.

Three GPS satellites help to get the exact position in three-dimension-  east, north, and altitude and a fourth satellite for accurate time calculation. The GPS receivers also know the exact position of the satellites in the sky, at the moment they sent their signals. So given the travel time of the GPS signals from three satellites and their exact position in the sky, the GPS receiver can determine the position in three dimensions accurate to 11 ft in horizontal distance.