 So, we will start from the basics, what is remote sensing, why remote sensing, where did it originate, how it has evolved over time, okay. What is remote sensing, so if you are seeing me it is remote sensing, yes or no, if you are looking at the slide it is remote sensing, so everything is remote sensing unless we are in come in contact, so that's what. So, we always use remote sensing, right, how did this word originate and what is the origin of all this, what is the origin for remote sensing, what was it, photography, so how did photography originate and what is photography means, photography meaning image, I want literally meaning that word by word what the dictionary should give, what is it, photo is light, graph is drawing, that is what it is, you make things from light or light drawn that is what the image is, that is what is photography, okay, what is the origin of photography, was it there 200, 300 years back, so 1838 Louis Degare was the one who evolved or who made these emulsions so that visible spectrum at least can be detected. In 15, 8 I think it was the balloon photography before that there was nothing and then finally 19, 10, 12 that is the time Wright brothers invented the plane and that has given a flip and the first world war, any progress in any discipline is because of, progress in any discipline comes because of, what is the compulsion, war is the root cause of every progress and every destruction, that is it, so 1914 the world war has given a good flip to the aerial photography, okay and until that time it was pigeon-tied you know cameras, photography and then balloon and all that 19, 10 Wilbur Wright, that Wright brothers invented plane then aerial photography and the world war, of course any technology gives an edge, it is both-sided right, it is at two sides of a coin, it has a neighbor also can see what is it gives, you can look into their territory but they also have that edge and of course the first world war has given a good flip to aerial photography and finally leading to photogrammetry, photography means who is interested, finally you should be able to interpret for the forces, that is what it is and then finally it went to second world war has given beyond boundaries of visible spectrum, infrared and all that have started that is what you know our people army, security people use what type of clothing, outer, color, green, so that green you know they can be, they can't but in infrared photography that can be differentiated because the moment you cut the branch it loses its contact, so it can be detected in infrared photography, so that is how infrared photography got a flip in second world war and of course subsequently this all this is because of the, why military, why war then requires this thing, what is the origin, why war requires all this, you would like to have an edge over your neighbor or to whom you are fighting with right and you want to protect yourself, your society of course living apart the expansion plans that I have to enlarge my holdings, my boundaries, whether it is my own or countries or whatever it is, so that is it, so photogrammetry came in a big way, photogrammetry, metry is measurements that is how it is and later on that turned out to be you know Elvin I think I have given in the notes, Evelyn Prutt an US naval officer in 50s have coined this word remote sensing that is how it has come from photography to photogrammetry to remote sensing that is the how this has come in, so what is it that we can do with remote sensing although there are many energies like acoustics, electromagnetic spectrum and these you know electrical resistivity, so many but here we exclusive deal with EMR or electromagnetic spectrum and its interactions not beyond that and of course there are active sensors, passive sensors, active sensors are the one which are microwave related and passive sensors are the ones which normally uses sun's energy of that remote sensing, I think you have already talked about anything about you know which is not in contact anything, so what are the various phases of remote sense, so it interacts with the matter and then transmission to this is what sun's energy comes and then it gets absorbed reflected transmitted whatever it is reflected energy is being detected by the low altitude aircraft or ground truth and then mid altitude or higher altitude and then finally satellites, this can be collected in ground truth in terms of you know normal measurements otherwise it could be in terms of pictures or digital data and then have this some ground truth data and then combine them and analyze and make the interpret interpretable maps so that the users or the experts can finally give the outcomes of all that, so these are the various facets of remote sensing and then what is the origin origin is electromagnetic spectrum electromagnetic spectrum is why it is called electric and magnetic these are mutually perpendicular directions and that is why it is called electromagnetic spectrum this is the spectrum that we this energy that deals with you can see sun's what is its temperature at the core temperature of the sun at the core is about 1 pro 50 lakhs degrees Celsius what is its surface temperature surface temperature is about 5500 to 6000 you can see since that is the 6000 K and at various case if you see you can see the earth's emission or what do you call it's not you know it absorbs and pre transmits and that is about 300 K that's why our atmospheric temperature in general approximately it may slightly vary is about 273 300 minus 273 is about 27 degrees centigrade that is how this 300 so is it electromagnetic energy or that what only sun is the capable or anywhere else any other do we transmit energy yes sir no no I mean we don't how do we feel warm when we wear the warm clothing because of what it is not that you know there is a always radiation anything above the zero 273 K yes or no should that's it every living being for that matter even most of the non-living things also are above absolute temperature yes or no so that it has to that is what warm clothing is not doing anything except it is preserving whatever that you are emitting that's it so every object which is about the absolute should emit energy sun you can see at what temperature that surface temperature and the earth at 300 degrees K you can also see the maximum at what is the emission at a particular wavelength for sun it is about 0.5 micron micrometers and for earths for 300 it is about 10 why should it come we'll come to that little later so this electromagnetic energy if you see is it that all that energy that is being emitted gets transferred to the ground does all of that come absorb then some and some gets transmitted now what comes is only that much of energy you can see the windows that you are seeing these are only the you know windows through which it can come or get back rest of it these are all blockages in a in a natural or absolutely transparent system that would have been actually uniform energy source if there's no atmosphere everything should have been coming if everything would have been coming we would not have been living these are all for our survival otherwise probably UV radiation would have eaten away long back there's no question of having you know anything like so these are the things how do they get absorbed ozone in ultra ultraviolet and in the visible and infrared spectrum it is mainly the water carbon dioxide these are the things main things which absorb so those absorb in the open the transmit windows are shown as UV visible infrared and of course this is beyond 1 mm or beyond that is microwave higher wavelengths why it is called infrared here and ultraviolet ultra should be more or less ultra is ultra is less meaning of ultra less meaning of infra everybody agrees that or anybody meaning of ultra is more in fries less but if you look at the wavelength ultra is less than the violet and infra is more than the red it is not in terms of wavelength it is in terms of quantum of energy that it is ultra lesser the wavelength it is more the energy more the wavelength it is the less than that is the problem of detection at higher wavelengths okay so these are the windows through which it comes through and the visible you can see at the center yes or no and that is visible range is 0.4 to 0.7 okay tomorrow will be our water resources but just see two-thirds of the globe is covered with two-thirds of the body comprises of chance are designed if you see the maximum transmission including the previous one if you see from Sun is enough 0.5 and 0.5 is in the visible spectrum yes or no that means maximum energy that what we can see is being received from the Sun in that wavelength accident or design okay and there are many more things that will come so that is one important thing because we can see in color do we what is the reason every animal can see the eye of course the new concept has slight change supposed to contain cones and rods cones are less in number rods are many more in number in terms of this so cones discriminate color color viewing and the rods are for intensity of light if rods are malfunctioning one is night blind because he can't see the light unless it is a very bright light night blindness you are aware no and of course if the cones are non-functional he becomes colorblind that is what the traffic inspector asked us when we go for driving license provided of course it is not the other way around when we go and if you want test he says can you discriminate the color green red and all so we are fortunate and we can see in 3D 3D you know yes in photogrammetry that is what actually these aerial photography has given a big flip because you can see in 3D you can measure the hives that is the advantage so do the animals see in 3D it depends if they have a converging eyesight it should be able to see if they have diverging if this nose is so big or something where I can't match my eyesight that is you can see similarly the color not that all animals can see what is it but much is crocodile cannot see this can only give in gray areas some of the birds can see some of the animals can see like monkey and others but not everything it is the absence or presence of cones so are we fortunate to have a 3D 2 3D means both eyes should be functional and of course color viewing all that so probably we should be one of the fortunate spaces to what is electromagnetic radiation quantum is it wave theory is acceptable or quant quantum theory h into new is queues equal to quantum theory C is equal to lambda into new is the wave physics are they both are okay particulate theory or particulate physics and the wave theory both may lead to same thing but you can't say that is only that or this so what is the truth truth is unknown what we know is only interaction whether it is in remote sensing or something what is interaction when I interact then is how you judge real color or anything that can we see the real color what is the color of that curtain approximate it doesn't matter whether it yes right okay right but is that the true color true color so what is the true color if it is no what is the true color if it is true color other than red is the true color so truth is never known what is that we see is an interaction if there is sense energy on that electromagnetic radiation and if our eyesight is in the visible spectrum then we can see night time you come and see in the pitch dark can you see it says right so truth is never known it is what we perceive so-called truth is only interaction I ask you to do some work you will say yes he's a very good person you refuse tomorrow what is that we judge people because of our interaction is it the truth is good or bad so so also in science what we perceive to be truth I am not saying that okay it is not it is not right please don't tell quote outside and then they will think that we are all you know should go to Thane hospital but that's not what I mean what I want you to go in deep is real truth is unknown what we hear is at the end of spectrum of audibility what we see is it the end of the spectrum of visibility the whole from you know zero to infinity there are many wavelengths can we see we have our limitations what we listen what we see is only limited saying that beyond this room is all empty this is the whole world is something like that so what is finally how do we go to it science and spirituality should go in search of reality to know the truth what we perceive is only within the within our limits that is what we are unless infrared was found can anybody accept that it is infrared beyond visible spectrum we can't we can't listen many sounds but does not mean they don't turn they do not exist so the energy both of them if you combine that is what HC by lambda that is where H is the Planck's constant I have given the values C is the velocity of light lambda is the wavelength that is what the quantum enjoys will come radial spectral excitance as per the wavelength is m lambda is equal to given by these ready to constant C1 C2 and lambda is given by that that is and that if you integrate between zero to infinity the total spectral gradient excitance m is given by sigma into d to the power of 4 where t is the temperature and finally the maximum wavelength at which the maximum transmission takes place is a by t where a is a constant 2898 divided by the oh yeah this is it so for some if you see you can see 0.5 that is the maximum intensity whereas for these that 2898 by 6000 gives you 0.5 2898 divided by 300 approximately gives 10 microns and that is what is called maximum wavelength of the transmission and see that design or accident we are in that spectrum of that maximum maximum receiving the energy and we are able to see in that okay so what does the atmosphere influence in terms of absorption in terms of scattering okay what is reflected is what we see right finally that is what is detected so absorption absorption I have talked about what absorbs the then what is scattering rally my non-selective scatter what is a rally scatter if the interfering particle is less than the wavelength that is called rally scatter if my scatter is almost the same the particles have same sizes the wavelengths of for the interaction and the non-selective scatter the particles have most size non-selective scatter is the water droplets and all that this will be a overcast sky and that rally scatter is the one which normally what rally scatter what is the best example of rally scatter how does the sky look sky looks blue but in the early morning and late evening why is it so why is it looking blue why is it in grade and why not some other color scattering scattering is that that is blue lights get scattered so it looks blue in the early morning and evening it is so complete that even the long wave radiation will get so that is how that is right fine now but if that what are the seven colors that has been you know you put a prism and split it up in class 10 or 11 we have done this experiment in the school yes or no so many colors seven colors can you name them right GR whatever it is so first thing is violet second is third is we'll stop there so but sky is looking blue why it should not look violet why it should not look indigo one two why did it why did it choose third one wavelengths only but the shorter wavelength rally scatter is shorter wavelengths get scattered why is it so any answer answer lies again our eyes you know it is called the primary colors are RGB but why only RGB who found seven colors of white light being split hmm it's the Newton's all his discoveries are at the age of 21 or so later on he became a mint employee and did not do much but was the great thing that he has done so what is it I was asking you yes why why sky should not look violet or indigo yes any questions any answers because I can I is sensitive to blue green and red these cones are much more comparatively green is even higher than blue and red and the other color perception becomes difficult because very few cones are there that's why we feel the primary colors RGB people say but it is not the main important colors are we can split into seven it should be seven but the number of cones that are present to discriminate that particular color is quite less so we say RGB that is what it is okay so that's why sky looks blue because although it should have been looking violet or indigo but because our perception that is why even in seven colors we can discriminate all of them most of the time yes or no so that is the reason for that so when the light strikes it is all incident energy what is reflected energy is that is what can be detected what gets absorbed what gets transmitted is you know is that what finally we talk about only reflected energy yes or no so based on this reflected energy if you draw for some of these important features like a bare soil vegetation and water at various wavelengths you can see what is the percentage reflectance these are called curves reflectance curves for that particular feature can it be a signature spectral reflectance curves spectral signatures can be say at various wavelengths you can see how it is okay vegetation we take ups and downs is vegetation you can see in the visible it is something like this can you see please see there in the infrared it goes up you can see no there and then here again it comes down and slightly it goes up and comes down and what is it due to these are all you know the this is anyway green so green it is okay but what happens is chlorophyll presence in infrared the reflected energy is so much because of the chlorophyll presence that is how it shoots up in near infrared and similarly there are some water bands where it comes down because of the absorption and then so you can see reflectance curves spectral reflectance curves gives an idea about how the material behaves based on these curves you can detect the type of objects that is all what we do is it okay so of course this can can we call it a signature spectral signatures sometimes you hear this word spectral signature can we say signature signature is unchangeable bank walla will ask nowadays is the ATM and all that so but otherwise when you give a check sorry your signature is not matching come and say with time right everything changes yes or no from black thick hair to white sparse hair with time yes or no so from the very good actor like image to the old image these are all part of the time so also signature change if it is unique it can be called a signature but otherwise although some people call it as signatures is unchanging it should or what happens you take the extremities and take an average average spectral reflectance curves or something you can call because there is variation in terms of incoming energy there is variation in terms of absorption transmission reflectance and then the limitation of the detector all these things so you can't have absolute atmospheric conditions to be same always it keeps changing from day to day time to time yes or no so you simply cannot say absolutely it will that is what new thing that has come I think I have wrote a sentence or two about high-perspective signature it is at about 300 bands in that visible and infrared here it is 1 micron 2 micron 3 micron itself we feel oh it is an arrow thing but then 10 nanometers you can imagine 286 bands in that image so that gives little more about the minerals or something of that type but that is you know how to process such a big data that would be challenge as we always feel we wanted to if we don't have work we say complicated which are complicated things which are simpler yes or no yes otherwise where is our survival and then finally what happens when it becomes complicated we say it is too complicated we should simplify so we complicate and then thinking that high-perspective will give yeah it gives for a particular purpose then for general purpose it may not be yes or no that is so image acquisition can be done by photographic sensors we are familiar digital data that is what the reflectance is being recorded okay not an image form in terms of reflectance values and then finally satellites of course there are atmospheric satellites also right now I have not included them because we are interested in this you can see the difference between black and white photography and then infrared okay those that area this white area is what can you tell me what would be the same which one surface what is that in black and white how does it look so it is the in black and white you can see in color so it is the launch vegetation so that's why high reflectance high reflectance means towards white or black you can see in color this is a color processing of addition subtraction that is how all the three primary colors will give you about white and in subtraction in this is in case of you know the color positives that you can see now in color color natural color color infrared color infrared how does it come in case of color composites also blue green red are supposed to be primary colors but although there are seven colors right because of the cones blue green red so blue whatever reflectance in blue and green and red if you see that is what it is color natural color but green red and infrared are represented in blue green and red filters that becomes infrared or color composite normal color composite of course you can change so you can see the difference between the two this is infrared and then what is that in within the stadium it looks same what is it there also it goes like a lawn almost right if I see only the top picture so bottom picture huh yes yes okay earlier we used to use you know hockey olympics but later on we felt that because we don't have astroturf so we should have astroturf so we have astroturf astroturf looks like you know lawn but in in this infrared it doesn't because it is not it is not natural so it doesn't come and this is the greatest advantage of the infrared that got a flip in second world war first world war is the aerial photography itself and that is so that you can camouflage things can be brought out the really you know they put the branches being cut and put including soldiers that can come out very clearly infrared and that is so some of the instruments which you can interpret are the mirror stereoscope pocket stereoscopes where you can see in 3D two photographs with 60 percent overlap same area should be there at least 60 percent and that you can see in 3D it's like Chota Chaitanya in 3D movie yes what is it you are given a glass some color glass and then you can see that superposition of one over the other and when you wear those filters or glasses you will see here it is 60 percent overlap is same so you synchronize that you should be able to synchronize and see will as one model one model then you can see in 3D that is what is mirror stereoscope and there are of course plotting instruments which you can you know see I will not get into more details of that so what is image interpretation image interpretation is based on this once you see in 3D based on these are called elements of interpretation so once you see in 3D there are image interpretation shape size pattern tone texture shadow sight association ok these are the elements of interpretation based on the shape why do we call a pentagon a pentagon building you know the headquarters of the US defense establishment because it is in the shape so you can identify the shape size whether it is a swimming pool or for something else if you know the sizes you can right patterns is repetitive tonal changes that is what is the pattern so based on pattern you should be able to of course tone texture is of course the tone the way tones are represented in repetition patterns is a particular pattern a road normally you feel some width and lengths are more ok without shadows a building actually shadows will help you in interpretation without shadows it is difficult sometimes and the sight if you know the sight that you are interpreting that will definitely help you and association associated features along with that whether it is a water body is used for sports or is a tank for irrigation if you have associated features around that you have some lodges and all that where people can then it must be recreation so if there is nothing that it is a water body it could be used for that or if you have a dam that you see fine so with association you can increase the capability of interpretation there are various resolutions that we talk about what are they spatial resolution spectral resolution radiometric resolution and temporal resolution spatial resolution is in terms of the space that means each pixel in the digital images how much area it represents that is what is called spatial resolution and of course the present day it is almost 1 meter even 0.65 meters is the pixel size earlier the first 5860s it was Tyros for atmospheric detection and this and 1972 it was Landsat and that has opened floodgates because space sciences and remote sensing joined together and that is the evolution of all these present thing IRS or Landsat 1234 and then what is it our IRS 1A, 1B, 1C, 1D, P5 at the present date is Kato sat earlier to that water resources sat so from 77 76.5 meters to 36.25 meters to 23.5 meters to 5 meters and 2.5 meters is the order of the day in Indian satellite civilian 2.5 I think they are not giving to everybody but 5 meters yes anybody can get so whereas our view and these satellites have even 0.65 meters that is what is called spatial resolution anything and the spectral resolution is the bandwidth through which you are getting in terms of multispectral we have see blue green red infrared if you have in a TM it is 7 bands including thermal so that is there is in hyperspectral 10 nanometers continuously 10 nanometers that is what is called spectral resolution and radiometric resolution is so from this completely white sheet I get a reflectance yes or no and from completely black also I may get something now this is the quantum of energy difference between the two what I get as reflected energy yes or no if that I can divide into how many bits how many gray levels how many shades that is what is called radiometric resolution so if it is a 7 bit 2 to the power of 7 minus 1 to 8 bits 8 bits is 2 to the power of 8 minus 1 minus 1 not in 8 minus 1 so that becomes 255 0 to 255 0 is counted so total becomes 256 shades of gray so that many I should be able to do so now the present day satellites have 10 bit you can imagine 2 to the power of 10 minus 1 the earlier satellites were 6 bit 7 bit so that is in terms of 2 if it is binary it is 0 and 1 if it is 2 to the power of 4 0 to 3 0 1 2 3 like that ok so that is what is called temporal resolution so there is always can you have the best of all what is better spatial resolution is it more or less in space less of space less of spectral bandwidth more number of gray shades radiometric resolution and temporal resolution is what with respect to time with respect to time if I can have the same revisit capacity for the same area that is temporal resolution how much it is it depends on the satellite to satellite it started with 18 days or so with Landsat now they can be tiltable you know sensors with that you have much higher thing it can be almost few days later and that depends upon the orbital altitude same thing that is coming back without tilting without with tilting you can even see the same area in due course how does that you know how does how do you decide in how many days does it take if you see when the Indian satellite missions they launch the satellite so it is slotted into a particular orbit if you say 816 817 you know 700 it depends what is the pre-designed and what it is supposed to be how much should be spatial resolution all that it that decides so based on this you can say how much time it takes to revisit the same place and in how many you know times depending upon the how much area it covers in one go and when it comes back to that it all depends upon this you can calculate if you know the orbital height okay so that is what is temporal resolution is being decided now can I have best of all these resolutions yes or no the least that is the best spatial resolution maybe now right now 0.65 okay that are even less spectral resolution now hyperspectral hyperspectral has 286 bands or even more with 30 meters right now that is the thing and then ready meter resolution best 10 bits so is it possible all all the best best of all the words why the quantum of energy that is received depends upon spectral resolution if the bandwidth is more more incoming energy can be there yes or no that is spectral resolution and then spatial resolution if the pixel dimension is more can I get more reflectance instead of less more means will it be more or not so if you have less of spectral resolution less of spatial resolution can you get more energy and depends on that ready meter resolution can it be possible both both of them then what happens if you have to really have that then your sensor technology should that is what Landsat 2 Landsat 1 it was launched it was you know across track scanning whereas CCDs were developed later almost every pixel is being independently looked by a CCD sensor that is a little so why because signal to noise ratio should be high noise should be least ideally 0 so that signal to noise ratio becomes infinity so any quantum of energy that you give above a 0 it should get you should be able to do it but normally is that the case no signal to noise there is always a noise noise could be because of the other you know pixels which are contributing yes or no so and atmospheric one it is difficult so their signal that our objective should be signal to noise ratio should be less and that is taken care by the designing of the sensors so if the sensors are sensitive you can go for this if the sensors are not okay so that optimal thing that you know tradeoff exists between spatial spectral and ready meter resolutions whereas temporal resolution is for you to decide depending upon putting the satellite in a particular orbit based on that formula and what are called these you see in a TV daily almost they show the India and the cloud see it's going to rain or something yeah we have seen those are placed they are called what are they called satellite are the resource satellites are some sort of resource but it is atmospheric communication satellite these apple we have satellites our own that is how we get you know these transmission phone phoning as well as internet as well as the TV transmission is because of those satellites they are called these are the earth resource satellites and they are called communication satellites any difference is there orbit rate will be more for height for how much height it is communication satellites are supposed to be it should be looking at the same point of the earth always so that means its rate of movement will synchronize with the rate of movement of the earth so what is the orbital time for a communication satellite then 24 hours you put hours and then that means in seconds and you can get the height or is fixed for the earth that's it whereas others that is really 48,000 47,000 to 48,000 kilometers that is the height at which they should be slotted whereas these are all between 400, 500 onwards to 800, 900 like that all earth resource satellites because the orbital period is around 100 seconds 90 seconds like that you can calculate you put 817 or 800 kilometers you will get around that 900 kilometers gives you about 103 seconds