 Hello everyone, myself K. R. Viradhar, Assistant Professor, Department of Electronics and Telecommunication Engineering, Vulture Institute of Technology, Salafor. Welcome to a video lecture on Global Positioning System. Let us start with the learning outcomes first. At the end of this session, students will be able to identify the location of object using global positioning system that is simply called as GPS. Also apply the concept of GPS. What is GPS? GPS is a satellite based navigation system. Navigation means the process of finding the location, position as well as distance traveled by an object. GPS system consists of there are 24 satellites in its constellation. See this diagram. It consists of a set of 24 satellites which revolve around the Earth with a definite and specified orbit. This was first developed by United States Depends Department in the early 1970s and 1980s. So, later in the year 2000 they have introduced to the public. Now, everybody is using this for commercial purpose. This can provide accurate positioning 24 hours a day anywhere in the world. Fortunately, there is no subscription charges or setup charges for use of GPS. GPS satellites also called Nowstar. Nowstar means navigational system for time and ranging. This is architecture of GPS system. It consists of there are three segments. One is a space segment. It requires at least there are four satellites and there is a control segment which consists of control monitoring and tracking of the satellites. There is an user segment where you can find the location of this GPS receiver. GPS system consists of the following three elements. First one is space segment. It consists of a dedicated satellites for GPS and are referred to as space vehicles. Second one is control segment. It consists of a tracking station located around all over the world and also it includes master and control monitoring stations which are used to control and monitor the satellites. Next third one is user segment. User segment is a GPS receiver used to receive the transmitted data and compute its position. This is where you are going to find the GPS receiver's position. Here we are using the concept called trial attrition. Now we shall clarify what is the difference between the word triangulation and the trial attrition. Pause the video think and write what is the difference between triangulation and trial attrition word. Trial attrition is the concept of measuring angle, but whereas trial attrition is the measurement of distance. How GPS determines a location? In order to determine the location of a GPS system we need to have minimum three satellites among 24 satellites. Three satellites are used to find the location of the GPS receiver or an object or four satellites is used to find the height of the object above the sea level. So minimum three satellites how they are going to determine the location of GPS receiver. Suppose GPS receiver is at this location or you are in this location, its satellite A is at this position. If it distance between these two will be measured first and draw a imaginary ring around this satellite. So satellite B also in this position you measure the distance between these two this is called the radius of this ring and it is forming there are two points point A and point B. So we do not know the exactly which position GPS receiver belongs to whether the position first one or second one that is why one more satellite is required. Satellite C forms another ring which meets at this point this is our position of the GPS receiver ok. So only with three satellites you can identify the location of the GPS receiver, but you cannot find the distance on which the above the sea level the GPS receiver exists. This will be explained later how GPS determines the location. In order to determine the location of object the things which need to know are current location of the GPS satellite, the distance between the receiver's position and the GPS satellites. We shall see first one current locations of the GPS satellite. GPS satellites are orbiting the earth at an altitude of 11000 miles. So which are away from the earth the orbits and locations of satellites known in advance these will be known because the orbit will be fixed and the locations of the satellites also fixed. GPS receivers stores this information for all of these GPS satellites in an almanac. Almanac means it holds the time, date and location of all the GPS satellites. This almanac is present in the GPS receiver. All 24 satellites are divided into six parts because 24 satellites will be divided into six parts each will have a satellite of group of four. There are four satellites in each part. A definite orbit is defined for each satellite because all the satellites are fixed and their orbit will be free defined. Each of these 3000 to 4000 pound solar powered satellites are used. So these satellites use that is having 3000 to 4000 pound solar powered cells. Next one is second one distance between receiver's position and the GPS satellites. By measuring the amount of time taken by radio signal that is GPS signal to travel from the satellite to the receiver or GPS receiver. We need to measure the amount of time taken from the satellite or GPS satellite to the GPS receiver. Radios travel at the speed of light that is about 186000 miles per second this is also fixed that is known thing. The distance from the satellite to the receiver can be determined in the formula distance is equal to speed into light. We know the speed of light, we know the time how much it takes to travel from the GPS satellite to the GPS receiver because we can measure the distance directly. So these are the some of the applications of GPS. So applications of GPS are public safety. You can use GPS satellites for public safety where you are moving and how you are moving that you can identify. Environmental resource agents aviation aviation is one of the applications where aircraft is in the space or moving with the GPS applications. Similarly we can identify that is in a position of the object where it is available and local planning also you can use it. Next is one of the application is surveying, surveying where you can land survey that is site survey etcetera you can use. Next is used for the business. These are the some of the applications of GPS. These are the some of the references used to prepare the above PPT. Thank you.