 Hello everyone, I am Swathi Ghargay, Assistant Professor, Department of Civil Engineering from Walchand Institute of Technology, Solapur. Topic for today's session is Introduction to Remote Sensing. Learning outcome of this session. At the end of this session, learner will be able to define remote sensing, explain component of remote sensing and explain types of remote sensing. Remote sensing is nothing but the scanning of the object. So remote sensing is used to obtain information about an object without making physical contact. So from the distance collect the data regarding object that technology is called as remote sensing. Remote sensing use electromagnetic radiation ranging from short wavelength to long wavelength. Short wavelength example is ultraviolet rays and the microwaves is the example of long wavelength. Now we will see the components of remote sensing. This is the image I have taken from the internet. In that image all the process of remote sensing is explained nicely. See here sun, it is the main source of energy. The sun rays are falling on the object. Here it is the object is nothing but the surface of the earth and that reflected rays captured by the sensor of satellite and then it capture the image and then that image is sent for the another source for the removal of any error. If error is not there then it directly send to the source which is on ground that is called as the ground source and this is nothing but the transmission of that image or this is called as the process. And then all the collected data is analyzed here and after analysis all the information should be available and that available information is used in the various field that is nothing but the application of that field. So here C, A is the source of energy, B is nothing but the radiations and D is the sensor, C is the object which is going to scan and E is the transmission of that image from one source to another source and F it is the analysis done and then after analysis the available information is used in various field. So G is the application. So these are the components of remote sensing. See here sensor or the satellite itself it is a source of energy and see the radiations are falling from the satellite also. So there are two source, one sun is the source and one is the satellite itself it is a source of the energy. Now see types of remote sensing, there are two types of remote sensing. Number one passive remote sensing and second is active remote sensing. Active remote sensing, sun is the source of energy. Reflection of sunlight is detected by the sensor. What is the disadvantages of passive remote sensing? It works in only day time, it does not work in a night time so this is the disadvantages. Active remote sensing, satellite or aircraft is a source of energy, a signal is emitted by a satellite or aircraft and its reflection by the object is detected by the sensor. The picture shows the passive remote sensing and the active remote sensing. In the first image sun rays are falling on earth and the reflected rays are captured by the sensor in satellite. So this is for the energy sun is used so it is called as the passive remote sensing and here in the second image rays are falling from the satellite itself and that reflected rays the sensor of satellite is capturing. This is called as the active remote sensing. Now you pause the video here and answer the question. Option is satellite emitted a signal and reflection by object is detected by sensor. Then such a type of remote sensing is called as options are positive remote sensing, negative remote sensing, active remote sensing, passive remote sensing. You pause the video and answer the question. Here is the answer. If the satellite itself emitted a signal then it is playing a role of source. So this is called as the active remote sensing. So correct answer is active remote sensing. Now we will see the application of remote sensing. The remote sensing is widely used in all the fields. Few examples I have shown here remote sensing technologies have been applied widely in climate change detection, environmental monitoring, flood prediction, agriculture, resource exploration, mapping etc. Whenever there is a changes in a climate that certain changes captured by the sensor and it is delivered to the ground source and this is utilized for the climate changes detection. Same the flood prediction also can be done with the help of remote sensing and to develop map the remote sensing is commonly used. This vision is much more beyond the human vision. Now see one of the applications of remote sensing that is the global positioning system. Many of you are familiar with this global positioning system because it is there in the smart phone also. Now see how it works. The first satellite is generating some information that particular object is at a distance from the satellite. And it is derived by velocity and time distance formula. From that available information so it is generated that whatever the distance given by the first source that is first satellite but on this circle that object may anywhere. So only the information from one satellite is not sufficient. So there must be a second source of satellite. So with the help of second source of satellite it is generated some information regarding distance. So see here there are two common points of first information and the second information say the first point is A and the second point is B means the object may be on position A or the B. So there are two possibilities so this is also insufficient. So we need information from the third source. So use the third satellite and use that information given by the third satellite. So by referring that information it is confirmed that B is the correct position of the object. So minimum three satellites are required for two dimensional fix. But for three dimensional fix minimum four satellites are required. Why? Because satellite captured an image, satellite received rays and then it is forwarded to the some another source. At what time it capture the image and at what time it is sending it. So it takes some time. So time constraint we need a fourth satellite for the confirmation. So for three dimensional fix minimum four satellites are required. So this is just for the information four satellites must be visible from any point on the planet and the satellites are arranged into six orbital planes. The minimum number of satellites needed to provide full coverage at location on earth is 24. So you remember this is the common information regarding satellites in remote sensing. These are my references. Thank you very much for the listening.