 Hello everyone, welcome to the next lecture in our course, we are discussing about remote sensing data sets, data portals and some of the processing tools. The last lecture we started discussing about remote sensing data and we saw example for like an optical data set and different levels of processing. So in the last lecture I told you like there can be like four different levels of processing in remote sensing data and not all the sensors and all the satellites provide us all the four levels of data. It depends on what sort of goals the space agency has and what they envisage to give us. So just I showed you one example of different levels of data processing with an example of data acquired from VA era sensor which is essentially like an optical sensor. In the same way we can also define the data for other sensors like synthetic aperture radar, passive micro radio emitters, slider and everything. First we will quickly see some examples for each of the data set. This slide shows an example for the different products available from the Sentinel-1 SAR satellite. It is like a synthetic aperture radar satellite operating in C band. So here also we have different levels of data even in different modes like at the end of radar remote sensing lecture I told you it is possible to acquire data from a SAR satellite in different different modes. We can either improve the spatial resolution by decreasing the SWAT width or obtain data over like a large SWAT or obtain like polarimetric data like data in different different polarizations. All these things are possible from SAR satellites. Similar thing is also applicable to the Sentinel-1 SAR like an example is given here in this slide. Say if you look at the data the data can be obtained in different modes strip map mode, interferometric wide SWAT, extra wide SWAT. So these things will differ whether we want a large SWAT coverage instead of like a very fine spatial resolution or whether we want like a very fine spatial resolution but we do not want a wide SWAT it depending on our needs we can choose the data, we can program the satellite to acquire such data. Here also we have level 0 raw data which normally may not be given to us level 1 data can be single look complex or ground range detected. So ground range detected is like the slant range geometry of the data will be converted to ground range distance which we can use it for further processing whereas a single look complex will contain both the phase information as well as the amplitude information of the wave that is received. So these are like level 1 products what basically the SAR receives. Then further it can be processed as level 2 data like it can be given like Sentinel the agency Copernicus gives data in like variables related to ocean like ocean wind field ocean radial surface velocity and so on. So these are some examples for data from Sentinel 1 SAR products. Similarly if we move on to passive microwave radiometers where there are like different satellites available I am just showing you one example for the smalls data which is again like an L band radiometer dedicated for observing soil moisture, ocean salinity and even like free start date it is it can able to it will be able to provide. So the first level of data is the brightness temperature which we all know like calibrated brightness temperature values. So the level 2 level 2 is always geophysical products. So brightness temperature is not like actual geophysical product that is what like satellites observes. When you talk about like earth surface or its properties then you can talk about like soil moisture. Soil moisture is one of like the state variable of earth system or you can talk about vegetation optical depth which is like the water content within the vegetation canopy like you can think it in terms of like a 3 dimensional structure which holds water or it is maybe you can say ocean salinity product if it is over ocean all these things. So level 2 will be such data sets on a SWAT based product. SWAT based means like as in what the satellite covers they will give us the image. Then level 3 everything will be properly gridded to like a perfect grid like earth can be divided into various grids and the data can be perfectly populated into those grids and it can be given to us with different temporal scale maybe daily, 3 daily, 10 day ones or monthly products. So it is like a proper gridded product maybe we will get like data for every globe. Today we know that each satellite will have more than one orbit in a given day across the globe right. So all the things will be properly combined to get us like a global product that is one and level 4 say whatever the SMOS observes they are like fed into like another model and they will provide some other advanced variables as output. Say in SMOS level 4 we also have like a very high spatial resolution product like at 1 kilometer they are using like a disaggregation algorithm to do it. Similarly, if you talk in terms of SMAP satellite which is another L band radiometer available in space again level 1 data is brightness temperature, level 2 data is soil moisture at SWAT level, level 3 is like global gridded daily soil moisture product and level 4 can be a root zone soil moisture product or like a modelled 3 hourly soil moisture and so on. So essentially these satellites passive microwave radiometers provide data related to brightness temperature, soil moisture or some of the passive microwave radiometers may provide even like wind velocity over like oceans, sea ice thickness all these things also can come as output from passive microwave radiometers. Then this slide shows example for LiDAR data products from ISAT satellite, ISAT 2 satellite basically from the Atlas sensor here also we have from level 0 to level 3 data. So level 0 is whatever the satellite is sending and level 1 data is actually like the level 1 data is basically the reformatted telemetry data whatever is sent by the satellite it is converted into science units under like the distance basically nothing much but the distance and other parameters. So when the distance is combined with the precise orbit determination parameters and the precise position determining pointing parameters like where the satellite is pointing and what the satellite orbit is. If these two are combined then we will be able to estimate the ground coordinates of each and every point that is the basic principle of LiDAR system I told you. So that is also possible that is level 2 data set. So this level 2 data set will tell you like the geo located photons where like each photon hit its XYZ coordinates it will be giving it will also give like a normalized backscatter profiles and all. So then comes level 3, level 3 is ok this is geo located photons after when you do processing over it we will be able to retrieve the thickness of ice thickness of vegetation and so on. So all these things are combined in given in level 3 land ice height, sea ice elevation, land or water vegetation elevation, inland water elevation like level of inland water bodies and so on. So all these things are level 3. So level 3 can further be classified to level 3a and 3b. So 3b has like a weakly product, gridded product and so on. So these are some examples of data sets available from ISAT to LiDAR sensor. So the major aim of me just giving examples of all these data products is to introduce the students who are new to this field to tell them about like the wide variety of data available. Conventionally we think everything as in form of like a image consisting of like spectral dn values, spectral effectance and so on but remote sensing provides a variety of data sources which we can directly use for many different applications. So that is the only reason I gave examples from different different sensors. Now we got like a very brief idea about what all the different types of data that we can get. Now we will see what are the common formats in which these data are supplied. Satellite has acquired some data, maybe an image or a non-image but everything will be converted to some form of like a computer readable file format and then it will be delivered to us. What are the common remote sensing data formats? Again I am telling this list is not exhaustive. I am just mentioning three of the most commonly used data sets. There can be many different data formats available but we cannot list and explain all of them. I will just pick three of the commonly used data. The first one is like the geotip format. The most conventionally used format for images say when you acquire LANSAT image or when you acquire like any IRS image Indian remote sensing normally you will be getting the image in geotip format. Like all the image each image will be kind of like you can think it in terms of like a photograph like we can keep it in analogy with a photograph. You can it is like a photograph of earth ok. So which you can visualize and like there are like special softwares to open it. Commercial based as well as open source freely available softwares are there to open it and visualize it. So everything is image it will be composed of like pixels like many pixels will be there each pixel may contain a DN or a reflectance and so on. So each band will be represented by one one image. So for a LANSAT satellite you can contain say LANSAT 7 had like seven different bands plus a panchromatic band. So seven different bands plus all will have like total eight images. So each image corresponds to each band like that. But the only difference between a normal photograph and a geotip is like and the common man language I am telling it is the addition of geographical information. In our normal photograph we just take a photograph it will contain the DN values that is it. But here since it is like a photograph obtained over earth each pixel will have its own coordinate information. So in general for an image you need to provide over which area it is taken what there is something what is called like projection there is something called data maybe students coming from the survey background may know all these things. Say they are all useful for defining the exact location over which the image was acquired. So those information will be there attached with this TIF. So it is like a normal TIF format tagged image file format but with geographic information one of the most widely used format for imaging sensors especially in the optical domain. Then comes hierarchical data format HDF. So this HDF is one of the very widely used format for dissemination of data acquired from different satellites especially like sensors like MODIS, VAIRS, SMAP even like some of the Indian sensors nowadays mostly give data in the hierarchical data format. It is like highly structured data format and also helps us to save memory like normally a geotip image may be like of enormous size. If we download try to download like a Landsat image it may be close to like 1 GB. Whereas if there can there each image can multiple variables just think of like a level 2 or level 3 product which can be which can contain several variables. If we store everything in geotip it will become like huge enormous amount of data. So HDF provides like a simple structured format where we can store the data. So one example of HDF data is given here in the slide. So this is like taken from SMAP L3 satellite L3 data product. So hierarchical data format basically contains groups as like their primary object within the groups there can be further subgroups or the actual data sets. So here if you look it has 3 groups metadata is one group soil moisture retrieval data AM is one group PM is one group. Within this you can have several other maybe like data sets or another subgroups on so one say for example land cover class latitude longitude water body fraction all these things are basically data soil moisture itself is a data all these things. So basically it provides kind of like a hierarchy. So it is each one will be kind of like will provide you data you can store a large number of data you can think it each one as a separate band if you think it in analogy with geotip ok. So each one can represent either one data or some other information about the data or like metadata ok. So it provides kind of like a hierarchical structure. But the only thing about like hierarchical data formators there are a lot of softwares available to open them but at the same time it is also easy to process everything using like automated computer codes also like we can just open them there are like again different libraries available in various languages MATLAB, Python, R and all where we can open them and process them highly amenable to computer processing. We can just extract whatever data we want and without need to need to open like the entire data set that is there. The next commonly used to again format is net CDF, network common data format similar to HDF5 like HDF5 is like the version HDF5 fifth version of HDF format. So it is net CDF also similar to HDF and most of the climate related variables and all are given in net CDF format ok. So these are some of the commonly used file formats as I told you earlier there are again many different file formats available and most of the softwares either commercial or opens or softwares are capable of opening this and also if you want to program everything with respect to some sort of programming language again there are specialized packages to open these data sets and use it. So this concludes our discussions related to different data sets that are available just a very brief discussion with few examples. Then we move on to remote sensing data portals ok different data sets are available that we now came across but from where to download all these data sets. So the place from which these data sets can be searched and downloaded or called data portals. Again there are large number of different portals available again we will discuss only some of the commonly used portals and almost all the portals require the users to register beforehand and they will send us some user ID password and everything. Once we have access to it we can search whatever data contained within it and download the data. This is one thing and the same data set can be downloaded from different different portals. So each portal is kind of like a small gateway you can think like the data will be stored in some server located somewhere physically. So the data portal acts as a gateway it acts as an interface between the data server and you. So what happens as a user I will be searching for a data set. So it is like a very big building having different gates same data server is there somewhere but through each data portal we can gain access through. Search the data ok what the data can like I may be interested collecting data acquired during month of October 2020 over Mumbai. I can search such images maybe from Landsat satellite or Indian remote sensing satellite like that. So the data portals will give me capability to search the data. Then I should be able to download it. Again that capability should be provided. So there are like different data portals available we will discuss some of the commonly used. So these are some of the commonly used data portals United States Geological Survey Earth Explorer, NASA Earth Data Search, Copernicus Open Access Hub, ISRO's Buvan and ISRO's MozDAC. So these are some of the things we are going to discuss but again there are like plenty of other data portals like there is something called NSIDC National Snow and Ice Data Center located in United States of America which gives us access to SMAP data sets, ISAC 2 data sets and so on ok. So there are plenty of data portals available but we will restrict our discussions only to these. So first thing we are going to see is like the USGS Earth Explorer maintained by United States Geological Survey. The web link is given there earthexplorer.usgs.gov. One of the most popular web portal for searching and downloading publicly available space bond and other derived products. Basically it helps us to query the server query means like we can say ok this is my need get all the data for it. So we can search for the data have a look at the data what we call like look images ok. So we need not download the data immediately we can just take a look how the data is especially for imaging sensors we can take a small look how the data is then we can download ok. So such facilities are available we can search have a look at the data and then download it. Not only satellite images but also thematic products such as land use, land cover maps, elevation information are all available. One of the most commonly downloaded data from this portal is the Landsat series of satellites. So Landsat series of satellites are widely they are kind of maintained by United States Geological Survey as the primary what to say maintainer maintenance provider. So the data from Landsat satellite are primarily housed here. So this is mainly used for that. Apart from Landsat we can also download data from Hyperion which is a hyperspectral sensor even commercial satellite images like Iconos and Obview 3 they are available. Then apart from satellite images you can download digital elevation models like I told you what digital elevation model is right basically. So that DEM is available from it. We can also even search and download data about modus, Aster even Indian remote sensing series of satellites resource at 1, list 3 sensor, resource at 2. Many things are available from this data portal which hacks us like a gateway to multiple different data. So this is how the portal will look. So the search criteria the first tab here we can just feature mention whatever feature we need to search. We can either search based on a location or we can draw like a small polygon on the map on the right side and we can decide over this you tell me like that we can use or we can give some coordinates. I have certain ground points X, Y values if I give it then it will deduct those ground points display in the map and search data for it that is possible. We can search the data which range to which range what fraction of cloud cover I need. Normally for some application we may require data containing less than 10% of cloud. We can specify that result options we can specify some search options and so on. So after this we click this tab and go to data sets. Once you go to data sets we have like you can just see how much different varieties of data available aerial images, AVHRR sensor, digital elevation model, EON, satellite, HCMM one of the oldest thermal mission, Landsat, NASA LPDAG which is like the MODIS VIRS collection, Sentinel all these things even Istro resource set. Many different data products are available. We can search them and download them through this data portal one of like the widely used data portal. The next important portal is NASA Earth Data Search. Again like the web addresses search.earthdata.nasa.gov. If you remember the name of the portals you can just search them in any of the commonly found search engine and get access to it. You need not even remember the web address. You can just remember okay this is USGS Earth Explorer portal, NASA Earth Data Search. If you remember the name you can just search using any of the common search engines you will be able to land up in those portals. So, that is like the beauty is so highly used we can you need not even remember the web address basically. So, the NASA Earth Data Search portal provides us access to almost all of NASA's earth science data holdings okay. So, whatever data NASA collects with respect to earth most of them are available in public domain and almost all of them are available from this particular portal. Not only satellite images data from model, ground based experiments like in-situ observations, airborne observations, everything is available in this portal whatever NASA thinks it can be publicly given they give you through this particular portal. Also this portal you can download near real-time data as soon as a satellite acquires data we will be getting it. This is highly important for meteorological applications or say volcanic observations, fire monitoring natural hazard monitoring for all these applications we need near real-time data that can be downloaded within few hours of data acquisition that will come to our hands or some data may have like a small lag time say 2 to 3 days, 1 month etc. Based on it the lag time the process data will come to us. So, all different kinds of data are there in this particular portal and there are plenty of options we can specify from which instrument we want. Say modus sensor itself is available in two different satellites Terra and Aqua whether I want data from Terra modus or Aqua modus I can specify. VIRS sensor is available in two sensor JPSS and Suomi NPP we can search it like this many different satellites are there. Here again not only images but also thematic products are available like you can choose list me all the data related to atmosphere it will list whatever is available then we can say list me all the data available to land use land cover it will list. So, not only based on satellite images also based on the theme in which you need the data I need data all the data related to global vegetation it will list from which we can choose like this that kind of facility is available in earth data search. Say this is like the general look of this earth data portal website here we can choose the date range here we can choose how we are going to give our location over which we are interested we can either give them in kind of like a bounding rectangle we can draw like this we can give like a polygon like if I want data over like this part of India I can choose it like this it is a polygon I can give a point ok search me data at this particular point or if I want to acquire data over New Delhi search me data acquired over New Delhi it may give I can draw like a circle and give so all these options are available then just see like a different amount of data it shows 7104 matching collections that is that much amount of different data products are available. So, whatever it is there it is just listing so 7104 different data sets with varying spatial spectra and temporal translation are available in this particular portal. Again we need to register before even we search or download a data you can see earth data login definitely we should register get a login and then only we will be able to get access to the data sets. And apart from NASA the other main space agency that gives publicly available space remote sensing data sets is like the European Space Agency which is the data portal is the Copernicus open access hub. So, again the website address is given here. So, the Copernicus data hub is an interface developed by the European Space Agency and it provides free access to Sentinel products. So, Sentinel 1 SAR data, Sentinel 2 optical data, Sentinel 3 is kind of like it provides sea surface topography, land surface temperature and also it is thermal and combination of thermal and antimatter data all these things. So, all these data are available from this Copernicus open access hub. See again this is how the portal will look we can like search by date range we can search which mission we want we can specify which platform like Sentinel 1 is available Sentinel 1a, 1b, Sentinel 2 satellites, Sentinel 2a to be like this we can search and here we can draw small bounding box with which we can search the data. So, this is again like one of the popular use data portals for searching and downloading Sentinel data sets. And among these portals NASA earth data search also provides us like a bulk download option bulk download means we can say for some of the applications I may be needing years and years of data I may want to analyze last 10 years of vegetation data for my application I need to do like a time series analysis. I cannot just keep on click download button so many 1000 times to download all the data it will give us like a single text file which will store all the URLs of all the data sets we can do some sort of like automated scripts or use some sort of like downloading softwares if we feed this text file as input to them the download will happen automatically like overnight you can just put the download go and come back and morning we will have all the data downloaded if our network is really fast. So, such kind of facility is also available and it is there especially like in NASA earth data portal which we can directly download. One more commonly used portal is ESA's EO Catalog which is European Space Agency's Earth Observation Catalog again the website address is given here EOcat.esa.int provides search and data download facility to many common satellite data sets allows Pulsar which is like a L band SAR data SMOS, NBSAT, SPOT, Landsat SPOT is again like an optical sensor Landsat data so many different types of data are available this is not very widely used but still it has like enormous potential for us to search and download the data and the glimpse of the data portal is given here in this slide. So, this shows the search has been carried out for the SMOS science product for all the data acquired between October 1 to October 31 of 2020. Just a large bounding box is given covering like the entire Indian subcontinent and these are all the orbits that SMOS had over this particular zone within this particular date range. Then we are moving on to data portals developed by ISRO. So, ISRO has Bhuvan and Mohsdek as their like primary data portals. Say Bhuvan is developed by NRSE National Remote Sensing Center of ISRO. So, the web address is given here Bhuvan.nrse.gov.in So, it provides a platform to visualize, share, even analyze geospatial data products. Not only we can search the data and download but we can also do some sort of simple geospatial analysis like some of the thematic products say land cover map is there like ISRO is doing lot of thematic works also they create land use land cover map they use vegetation maps and all. We can just normally in our GIS software we can just take a link out of it. If we put the link here the data will be available in our GIS software over which we can do our analysis that is possible. So, it is also provides us some simple analysis tools. It has lot of capabilities actually ISRO conducts lot of training programs online webinars etcetera to educate people about the usage and the huge variety of application for which these portals can be used. I just briefly introduce you people with this portal. Please feel free to explore and there are like plenty of online resources available that are created from the ISRO side itself. So, the Bhuvan enables us to like do visualization of satellite imagery, maps also its analysis and whatever data is publicly available from ISRO we can search and download it. In addition to satellite data several thematic products related to land, ocean, atmosphere and cryosphere also available from this portal. I need land, vegetation it is available. I need some variables related to ocean available, atmospheric products available. So, all these things are we can do it. In addition to it from the NRSE site we can also search for IRS images some of Indian remote sensing satellite actual images we have to search for it order and pay some small money to get it that facility is also available the links are available within the portal. So, as I told you earlier in Bhuvan portal users can also use the thematic data sets in the portal and integrate into their systems as OGC web services that is open geospatial consortium web services. Whatever data is there we can use it into our own applications, application the sense like I may have some software running in my computer I can I may not able to download all the data, but I can just take a link out of it where my software will work with the data along with my own data sets combine everything do like an integrated analysis that is possible with the data available from Bhuvan portal. And it provides timely information on various parameters especially natural hazards heavy rainfall, droughts all the again information will be provided in the Bhuvan portal. Say this is like example of how Bhuvan portal will look. So, this open data archive will take us to some of like the freely available data sets we can choose which satellites and sensor we want which team or product we want like this we can choose. We can see this 2D and TD 3D portals provides us visualization we can visualize various data sets it provides thematic services it provides data of in different application sectors what is needed for agriculture what is needed for hydrology special all these things are available within this portal. If the data is not directly available within this it will also provide us the links from back to get it within like the Eastrow's domain. So, that is the advantage of Bhuvan portal one of like the highly popular data portals developed by Eastrow where almost all the Eastrow data products can be searched and accessed. So, the next data portal which we are going to see is like the MOSDAC which is like the data repository again created by Eastrow but from meteorological missions. Say mostly it contains data acquired from satellites dealing with meteorological applications oceanography and tropical water cycles. Say MOSDAC portal archives and disseminates data from satellites such as INSAT, Kalpana-1 which are all geostationary satellites, Oceansat, Megatropic, Saral all these things. So, there basically it is for meteorological and oceanographic applications developed by the most of the data are like available from the space application center like the earlier the Bhuvan portal was from NRSE national remote sensing center and this one it is from space application center. But everything is like different arms of Eastrow but each one often specialization different different things. Again we have to register we can search for the data and download it. Say this is example for the MOSDAC portal. So, here we can INSAT-3A is one of like the geostationary satellite. Similarly, we have Kalpana-1, INSAT-3D all those satellite are there. The data catalog is provided for different applications you have datasets all these things are available from this thing. So, MOSDAC stands for Meteorological and Oceanographic Satellite Data Archival Center developed by space application center of Eastrow. So, again even for this particular portal Eastrow has provided online webinars which are available in various platforms which users can see and get expertise within this data portal. Apart from this Eastrow is also developing a portal called VEDAS which provides us some sort of like analytical capability. We can do some sort of analysis over the data for acquired from different sensors. So, as a summary in this lecture we have seen about like some of the commonly used data formats and also some of the commonly used data portals. I am repeatedly telling I have just introduced you to the data portals. So, the interested students they can explore more. So, and also one dataset can be available from many portals and some datasets can be accessed only from a particular portal. Say INSAT-3D data can be obtained only from the MOSDAC portal you cannot search it for anywhere else it would not be available. So, it is always better for us to know okay this is the satellite which I am going to use from where I can get the data. If we know this particular knowledge it will help us whenever we are doing some sort of research activity or a project activity. So, the interested students are always welcome and encouraged to explore all these portals and understand what are the capabilities of portal. They are not just data providing portals they provide other few portals provide data analysis capabilities too. So, we are always free to explore that. So, with this we in this particular lecture. Thank you very much.