GPS ( Global Positioning System) – working

The GPS stand for global position system, which is basically satellite based navigation system that provides the exact time information and location anywhere, anytime 24 hours a day and in all-weather condition. It is made up of 24 satellites network system and placed into the orbit of US department of defense. In the beginning it was started for military purposes but in 1980 the Government developed a system for civilian purposes. This system has no subscription fees or setup charges, basically its use is free of cost. This system is known as Navstar (Navigation satellite timing and ranging). It also has many applications in microcontroller based project.  A global position system is shown in figure


Segments of GPS:

The GPS based system consists of three segment or parts

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

GPS Space Segments

The GPS space segment consist of orbiting GPS satellites or space vehicles in parlance of GPS. This was manufactured by Rockwell international. This segment consists of 24 satellites and three circulating orbit. Eight satellite circulate in each orbit but later this was modified into four circulating orbit mean 6 satellite circulate in each orbit with 55-degree inclination angle and 60-degree right ascension angle. Their orbiting period is one half of the sidereal day.

GPS Control Segment

The control segment consists of a four dedicated ground antennas, six dedicated monitoring stations, master control station (MCS) and alternative master control station. The dedicated antennas receive the satellite transmitted signals and monitoring stations monitors the satellite to track their exact position in space. For make sure they are operating correctly. The master control stations constantly monitor the satellite and use the radar for checking the position, altitude and speed of satellite. The alternate master control station work in the absence of master control station.

GPS User Segment

The user segment consists of hundreds or thousands of user receivers that could be hand held or placed in vehicles. Normally the receiver consists of antennas for tuned the frequencies transmitted by the satellite, highly stable clock and receiver processor. It also consists of display screen for providing exact speed and location of user.

Coordinates of GPS

The GPS based system use geographic coordinate system which is basically a coordinate system that enables every location on earth with the specified set of symbols, letters or numbers. The coordinates mostly choose in a such of way that one number represents the vertical positon .and two or three numbers represents the horizontal position. The GPS based system use the three coordinates angle of latitude, angle of longitude and angle of longitude. Latitude is angle that specifies the north -south position of the point that exist on earth surface and its range is in between 0 degree to 90 degrees. Longitude is coordinate that specifies the east-west positon of the point that exist on earth surface. It is used for angular measurement and is denoted by Greek letter lambda. Latitude and longitude are mostly used together for displaying the exact location of point that exist on earth surface. The elevation is a coordinate that tells the exact height of the point with respect to the reference point. It tells the specified point is above or below the reference point.

Working of GPS

The global positioning unit takes the microwave signal in space from satellite, which circulate in orbit around the earth. In space there are almost 30 satellites which circulate around the earth orbit, each orbit has a radius 16500 mi approximately and 12600 mi above the earth. The GPS unit once receives the signal from north and south poles of 6 to 12 satellite. Each satellite has an atomic clock that is set by NORAD carefully a number of times in a day. The microwave signal contains very good position and time of satellite with its ephemeris. The GPS unit consist of a receiver that subtract current time of a signal from the sending time of signal and this difference tells from how much distance the signal is sent. This time difference is multiplied with speed of light for calculating the distance from satellite. This system uses the trigonometric function for solving or calculating the satellite position and distance. For solving the trigonometric function there should be must at least four equations. The GPS system is so fast it receiver calculate the position in less than one second and it calculates the speed and direction by changing the change in time and change in position

Sources of GPS Signal Error

There are some sources which generates the error in global positioning system signal.

  1. Satellite Geometry Error
  2. Satellite Orbit Error
  3. Multipath Effect Error
  4. Atmospheric Effect Error
  5. Clock inaccuracies and Rounding Error

When the satellite in circulating position then we calculate the time but we can’t calculate the exact time that’s why the error is generate for calculating the position and this error is called satellite geometry error. The error generates in the orbit of satellite due to the lightly effect of sun and moon waves resulting the satellite slightly drift from the orbit and this error is called satellite orbit error. During the GPS signal arrive at earth then it may be reflected by the local obstruct before by get the antenna receiver, due to this effect the GPS signal arrives at the earth with some delays and this error is called multipath effect error. Some errors are occurred due to the atmospheric effect such as the water vapors in atmosphere that errors are called atmospheric effect error.

GPS Module

module is basically the GPS receiver that is available in smartphone and many automobiles for social dealing between the people. This is a tiny device that can tell you, your exact location, position, time and also communicate with the other same tiny device. This tiny device composed of three components, GPS antenna for sending and receiving the signal, Micro battery for power on the GSP module and USB interface port for interfacing with your computer. When the data goes down to earth from satellite, that is actually in the form of different pieces of information and this data is received by the GPS module and calculate the exact time and position of this data. The GPS module is interfaced with your computer or any other LCD for displaying the data position and time. A GPS module is shown in figure 2

Application of GPS Module:

There are so many applications of  module some of which are given below.

  1. These are used in Nano Quad copter for monitoring their position.
  2. These are used in automobiles for the exact navigation of cars or vehicles.
  3. These are used in smart mobile phones for social communication between the people.
  4. These are used in smart power meters for the exact calculation of consumption power, for the communication between the meters and to overcome the problems of electricity stealing.
  5. These modules are used in Nano drones for the exact location and position of target.
  6. These modules are used in fish finder devices for catching the fish in easier way.
  7. These modules are used in that devices which are used for wildlife tracking.

1 thought on “GPS ( Global Positioning System) – working”

  1. Hello MALIK,
    I have been following your post for some days now which i got attracted and have interest in them.
    So, i love the GPS post and would love to know more of it. In the process of reading this post, Some ideas came to my mind which i think i will like to implement.
    How can i use the a GPS for solar tracking?
    I will to see your response as soon as possible. Thanks Bilal Malik


Leave a Comment