Awesome. All right. Well, I guess it's time for us to get started. So thank you, everybody, for coming today. My name is Hartmont Gummary, and I work for Hyperledger, and I'm going to be talking about decentralization and why open source development is essential for blockchain. So let's get started. If we're going to talk about decentralization, we obviously have to define it. So as many of you are probably aware, we define decentralization as the degree to which a single entity or group of entities control something. And you can obviously measure this in a wide variety of different ways, right? It could be measured as the largest proportion of control by any single entity, the number of entities it takes to completely control a system, perhaps, or there are more complicated metrics, like blockchain people are probably familiar with the Nakamoto coefficient or other metrics of decentralization. And if you're looking for an abstraction, you can sort of think of government, right? You could have an absolute dictatorship, which is totally centralized. You could have a representative democracy, which is sort of moderately decentralized. And then you could have a direct democracy, which is totally decentralized. But there are always caveats. And even if your protocol is decentralized in theory, ideal guarantees may not translate to practice due to external factors. If you have a direct democracy where everyone follows an outside opinion, that may not be decentralized. So I'm also going to define distributed ledger. So in the blockchain community, there's a big, I guess, language issue around what's a blockchain, what's a ledger. So I'll just put some definitions forward for now. So I define a blockchain as an append-only system of record or transaction log. So this is the immutability guarantee that you're used to in something like Bitcoin. Then I define a distributed ledger as a distributed database with decentralized trust. And if you think about, again, say Bitcoin, it has that decentralized trust property that we're looking for here. Most popular blockchains are also distributed ledgers. And most popular distributed ledgers are also blockchains. So I tend to use these terms interchangeably. And most people do as well. So if we think about what popular blockchain systems are abstractly, well, they're really just distributed databases with decentralized trust. Bitcoin is sort of a distributed database for what we'll call money with decentralized trust. Ethereum is a distributed database for, I call it programs with fully decentralized trust. And Fabric, for instance, is a distributed database with partially decentralized trust. It's not necessarily as decentralized as Bitcoin or Ethereum. So today, we're going to focus on distributed ledgers rather than necessarily the immutability property of blockchains, although our discussion will certainly apply to pretty much every blockchain that you think of today. So the immutability properties of blockchain can be great for a lot of public applications, but not always for enterprise solutions. For instance, if you have GDPR regulations, immutability can be a very bad thing. So the core property we'll use today is actually decentralized trust. So what is decentralized trust? Again, if we're thinking of a database or a blockchain as sort of a store of records, who gets to decide what records belong in the database? If one person or one entity decides, then we have a very centralized database. And if many different entities decide, we have a decentralized database. And again, trust is a continuum. It's not a yes or no situation. So technically speaking, and we'll go into this in a lot more detail, the consensus algorithm is the most impactful design choice on decentralization, but there are many other choices to make. So if we have our blockchains, we sort of have a continuum of fully decentralized to fully centralized. So the most decentralized systems are things like Bitcoin, Ethereum, Cardano, Ava, these public cryptocurrencies with proof of work or proof of state consensus, slightly less decentralized are distributed ledgers with BFT consensus. And we have several of these in hyper ledger. As we get more centralized, we can think of distributed ledgers with crash fault tolerant consensus. If you're familiar with what that is, it's a little bit less resilient than before. And finally, you know, eventually we reach traditional databases which are fully centralized. So why do we want decentralized trust? What's the reason? Well, there are many possible reasons why we want decentralized trust. For instance, we could have several entities that need to agree on some data, but no single entity trusts any other entity to be the source of truth. You know, we could have a store of information that needs to be made redundant in the case of compromise or attacked by a hacker. We could have a case where the entity that would be the best sort of official source of truth for something doesn't want to or can't be responsible for the upkeep of the data. And this is very common for government applications. And finally, we could have cases where the people responsible for maintaining a data set are dynamic in change very quickly, and we sort of keep track of all the changes. So if you take away anything today, and you know, the blockchain experts in the audience probably, I'm sure already know this, but the question you should be asking is when you ask, do I need a distributed ledger? You should ask, do I need a database with decentralized trust? And you know, if you're new and this is you're just learning blockchain, this is the one point to ask. If you need decentralized trust, you need a blockchain. If you don't, then you probably don't need a blockchain. So when you think about blockchains or whether you want to use a blockchain, you want to consider sort of what's the information being stored in the database, even if it is a programmatic database, and why is having one centralized entity maintain this information a bad idea or impossible or infeasible? And this will make it easy in the future for you to determine cases, whether distributed ledger is just hype or actually necessary. And so of course, people ask all the time, you know, are there real use cases for a database with decentralized trust? And obviously, because, well, you know, the answer is yes. I really, you know, I think this has been borne out by lots of real world use cases. We've seen widespread adoption and hyperledger of applications with real world value added to existing enterprises and, you know, that aren't connected to a lot of the things you see about token speculation. And I also think they're a great real world applications of public chains, too. So I don't want to say, you know, you should ignore public chains. I think they have great use cases, but they also get obfuscated by some of the less good applications connected to token value speculation. And I'm just going to sort of display a couple of slides. Just you don't need to read everything here, but just to sort of show you how widely technology has been adopted in this space. And this is just hyperledger stuff. Obviously, there's an ocean of blockchain applications beyond hyperledger. So one of our big applications is finance. It's a great area where people want distributed databases with decentralized trust. Maybe you've been following the CBDC or the central bank digital currency landscape. And this is sort of taking the world by storm. Supply chain is another big one. And if you want, I'll be happy to explain the rationale for all these use cases after the talk. I don't have time to go into detail about them now, but feel free to ask me afterwards and I'll explain everything. And many of you, well, may know about digital identity. Have people seen digital identity applications before? Yeah, this is another great case for distributed databases with decentralized trust or essentially blockchains. So I just have a slide about distributed ledger. You know, what does it look like? Because a lot of, you know, I get asked this all the time by people who aren't familiar with blockchain. So this is the high level architecture of Beisu. We have a database layer, a smart contract layer, a consensus layer and a networking layer. And I kind of want to go through this quickly because it seems like we have a lot of people familiar in the audience with blockchain. But have people seen this kind of thing before? Are people comfortable with blockchain architecture? Yes, no, maybe? No? Okay. Well, so I'll explain this. So a blockchain is usually sort of modularized into four parts. And there are four essential parts. How the data is stored, how the transactions are handled, which is the smart contract layer, the consensus layer, which is sort of the high level communication platform and the networking layer, which is sort of like how do the blockchain nodes communicate with each other? So before we go any further, you know, I want to emphasize that we should not always use distributed ledgers. A lot of people will try to oversell blockchain and I want to, you know, make sure that you don't come away with the impression that we should use blockchain for everything. So decentralization is a fantastic tool and it gives us a lot of great guarantees in practice. But there are always drawbacks to using powerful tools. And in fact, there are many issues with distributed ledgers, but there are two that I'll sort of talk about today and that's privacy and confidentiality and performance. So these are challenging issues. So does anybody know what this is? Or does anybody want to guess? Go ahead. Yeah, you're right. So this is actually my credit card history from a few days at the end of February, a few years ago. And it's anonymized, right? So, you know, if it were in the blockchain, you might see something like this. But you can learn a lot, right? So I have entries. I have transactions in the South Bay, right, on snack machines. Well, you're probably going to guess that I have some, you know, work scenario in the South Bay, right?  There's a corporate catering in Sunnyvale. You know, you've just already, you've probably figured out I work in Sun, I, at this point used to work in Sunnyvale. I'm buying gas and I'm getting groceries in Redwood City. You know, that might give you information on where I lived. Why do I have a payment to Stanford? You can make inferences about that. You know, I have a payment to a gastropub in Redwood City, and then I have Ubers. So just from sort of my transaction history, you know, you learned that in 2018, I worked in Sunnyvale. I probably lived in Redwood City. I had some connection to Stanford, and I enjoy going out for cocktails. And this doesn't totally de-anonymize me. But if we did this over a whole month, or even a period of months, you could probably, you know, completely figure things out. And being anonymous, you know, didn't really buy me much, right? And this is challenging, even in the permission setting. And privacy and confidentiality are tricky. So there are solutions to privacy and confidentiality, but you typically pay for them. So, you know, one of the ones I'll sort of just mention here is we have, you know, fabric private data collections. And the main idea is to limit the data others see on the blockchain by posting hashes rather than the data itself. But you know, this does come at a performance cost, right? You have to keep track of more data, you have to have extra mechanisms for dealing with data. So there's a trade-off. And this sort of gets to the blockchain trilemma. Have people seen this before? How many people have heard of the blockchain trilemma? A couple people? All right. So Vitalik made a reference to this, you know, originally at some point, I guess quite a while back at this point. But the basic idea is that it's very difficult for blockchains to achieve performance, security and decentralization all at the same time. And we have to consider trade-offs. So if we consider trade-offs like things like Bitcoin and Zcash are very decentralized and very security focused, whereas something like AOS, you know, trades some decentralization for scalability. I will encourage you if you are working on blockchain, please don't be here. Please don't sacrifice security. Choose your trade-off between performance and decentralization. And so if we go back to decentralized blockchains, and we think about performance, you know, in general, we do have that more decentralization leads to slower performance.  Ethereum is 30. Cardano is about 250, but we have some IOHK guys in the back who can probably give you better numbers than I can.  You know, even assessing the performance of some of these blockchains is very dependent on the network, how you set it up, how you configure it. So it's quite complicated, but it's the generally the more centralized you are, the faster you go. And then, you know, obviously traditional databases can blow blockchains out of the water in terms of performance. So there are trade-offs in distributed ledgers. So if you have decided you need a distributed ledger, it's important to pick where on a decentralization continuum you need to be.  And I will say there are tons of trade-offs in distributed ledgers. We can't really go into all of them. You have to be very careful when you're picking a blockchain that you sort of get the right balance for your application. But again, the main and most universal trade-off is sort of decentralization and performance. And if we think about decentralized trust, there are many different components of decentralized trust. So there's the code layer. So there's who implements and maintains the project. There's the architecture, the specification layer. And oftentimes, this is sort of, you know, combined with the code layer, but sometimes it's not. So who decides the specs? Who sets the roadmap for the project? There's the on-chain consensus layer, which I mentioned before. And there's the governance of the ledger. How do we govern the ledger? You know, what's the legal framework around the distributed ledger? These are all important. And finally, there's the application layer. So sort of all is for not if your application is not actually decentralized. So I kind of felt scooped because, you know, earlier this week, Trail of Bits came out with a very similar categorization and report. I don't know if has anybody seen this? Yeah, it's got a lot of news. And it turns out, you know, that Trail of Bits certainly thinks that many blockchains and applications are not very decentralized. It's hard to disagree with that. And the core point is that if any one of these layers is centralized and sort of controlled by one party, then the entire blockchain is more or less effectively controlled by one party and is centralized. And if you have a centralized part of sort of any one of these layers, you know, you have to ask yourself, why would I not just want to have this single party run the system in a centralized way? So let's talk about some of these. So let's talk about NFTs. So, you know, everybody here is probably seen or familiar with NFTs. Is anybody familiar with this NFT standard EIP 721? Yeah. So basically, EIP 721 explains how a lot of the common NFTs on Ethereum or Ethereum blockchains are stored. So most art NFT projects don't actually store the art itself in the blockchain. They don't even store a hash of the art. They just store a URL pointing to a website, right? So what if the website goes down or changes what the link points to? What happens to the NFT? Well, so there's a famous security researcher, Moxie Marlin Spike. I don't know if you all are familiar with him, but he decided to have fun with this. And he wrote an NFT that changed based on the IP address of the viewer. So sort of wherever the, you know, wherever the user was coming from or sort of, you know, how the website was interpreting it, changed what the NFT did. And he immediately got removed, which he was commenting, like, well, you know, shouldn't my NFT be forever? But the point is, if the website can change what the NFT points to it will, you know, is this just not total centralization? And sort of two paths for this application make much more sense. You know, why would you not say, let the website be the arbiter of who owns the artwork registered on the website and have it store the ownership? And why do we need a blockchain if the website gets to decide what art the owner of the NFT owns anyway? Or we could take a more decentralized approach and we could store the entire bit representation of the artwork in a blockchain, maybe even just a hash. And this would add storage requirements to the blockchain, but it would prevent anyone from sort of changing what the artwork represents itself. So I will say watch out for false decentralization when you're looking at blockchain applications. So this is very recent and I had to change my slides for this. So how many people were following the Solend situation? So very quickly, Solend is a ostensibly defy protocol, so decentralized finance that lets users borrow money and lend money without having to go through intermediaries. It's built on the Solana chain. So this is the claim from the website and I will emphasize that it's algorithmic and decentralized. OK, so what happened? Well, there was this big hullabaloo about you know, emergency powers on the Solana network. And basically Solend's largest single user came dangerously close to a margin call due to the Solana token price going way down. And if this users were, excuse me, if this users positions were liquidated as a result of this margin call, it was going to be chaos for Solend. It might even cause outages on the Solana network. So the Solend community passed a proposal to strip the user of control of their funds and to manually liquidate the user's positions. So this means they're taking this person's money and liquidating it. And after backlash, you know, there was another proposal that mostly canceled the first one. But you know, is the community voting to strip people of control over their funds really a good idea? And even more so, you know, a lot of both of these votes were essentially dominated by one person. So one wallet and for both of these proposals, you know, made the difference between them passing. So, you know, this obviously caused a lot of a lot of outrage on the Internet. There were comparisons to, you know, obviously Jar Jar Binks in episode six. But, you know, it might not have even been sort of an innocuous proposal. There might have been, you know, malice behind it because people stand to gain a lot of money from this liquidation. So in summary, you know, make sure your blockchain governance is designed so that they can't be centralized by malicious parties. And again, if we consider the next layer, right? So, so I already showed you this slide on on chain consensus protocols. But there are a lot of subtleties with consensus algorithms, right? So how many people here are familiar with mining pools? I assume most people, maybe. So you all know how these work. It's hard to successfully mine as an individual. So people come together and form mining pools, less money in the expectation, but you get a steady or stream of payments. So it's it's worth it to reduce the chance. But mining pools are centralized, right? And the mining pool operator controls what transactions the miners and the pool propose, you know, as well as what chain they build. So this is the current distribution of blocks. I think I pulled it a couple of days ago. So it's probably the past three days on like Tuesday. But these are the percentage of blocks mined by various Bitcoin mining pools, right? So essentially three pools have a majority of Bitcoin. So that's three people that essentially get to determine the consensus. It's the same case for Ethereum, too. About three pools, you know, form a majority. And a lot of people ask, you know, what happens when we go to proof of stake? Will it be better? So there are still issues with proof of stake, too. A lot of people have a hard time running their own node with their own ETH. So they join staking pools. And these also present centralization problems. As you can see as well, there are about three staking pools that control close to 51 percent. And I will say mining pools are difficult to fully analyze in terms of what they mean for decentralization. On one hand, users can always leave the mining pool if they disagree with its decisions. But on the other hand, users may be less happy with their financial rewards if they do so, right? If you join a smaller or less good pool, you might make less money. So the question you have to ask is will a rational user that cares mostly about their income be willing to leave a mining pool if the mining pool is a censoring transactions? So, you know, I just want to emphasize that it's necessary to address the full tradeoffs of consensus algorithms when it comes to decentralization, even for permissionless networks. And finally, you know, it's important to make sure that your decentralized protocol can't become centralized. So are people here familiar with the beanstalk attack? I thought this was very clever and it was actually quite legal. It was within the governance of the beanstalk protocol. So an attacker took out a flash loan, a flash loan without getting into the technical details is sort of a very, very fast loan. You get the cash and you repay super quickly. They bought enough of the beanstalk tokens to completely take over the protocol. So they sort of had more than 51 percent of the stake. They created a proposal to send all of the beanstalk protocol funds to their ETH wallet, which they then passed because they had all the stake. They laundered the money and profit it. So it's important to think carefully about whether your decentralized assumptions hold true. So beanstalk assumed that there would never be a single entity in charge of more than half of its voting rights, but that was obviously not the case. So moving on to sort of the next layer in the chain, it's very important that code and architecture design of a blockchain are also centralized. So here I sort of made up a traditional blockchain system this is how most blockchain development works. We have a blockchain foundation that I've called Silly Foundation here. We have Silly Chain and we have Silly Devs that are a part of the ecosystem. And typically the foundation manages the blockchain development, it may manage the chain and the devs are building applications. So what if one entity controls the blockchain development process? In theory, they could push software to the blockchain that maliciously broke the blockchain or try to steal value of the chain and get away with it. In practice, the entity likely has reputation at stake and value tied in their chain. So what we would mostly consider attacks are things that would sort of advance the entity's agenda at the expense of others, preserve their value, make them money. But in summary, you have to completely trust that the code development entity is sane, rational, and to a lesser extent honest, if you want to have a centralized development process, that's a lot of trust. And if Silly Foundation has completely centralized control over development, then the devs have to trust it. And in this case, you have to carefully consider the advantages compared to having this Silly Foundation just run a centralized database. People are probably familiar with this, right? This is a basic code snippet outlining the Ethereum DAO attack, if you are familiar. I think most people have seen that at this point. So the point I want to make here is even using a degree of centralization, right? So when the DAO attack happened, the Ethereum Foundation very quickly pushed out an update and said, hey, OK, everybody, please get on board with this fix. This caused a, you know, a lot of controversy, even though it was arguably doing a good thing and disincentivizing large system attackers. And this did change the governance, but I don't want to get into that right now. So what we sort of want when we have, you know, a foundation or something building blockchain code is we want to incorporate the community. We want it to be as decentralized, you know, as we possibly can. We want openness. And I will state that I think an organization developing blockchain software should be maximally decentralized. We want it to resemble a representative democracy of the stakeholders and people who contribute to the blockchain and its development as much as possible. So this means transparency, right? Decision making should be done in the open and also openness. We want anyone to be able to join and contributors should be able to reach leadership positions on their own merits rather than company affiliations. So we don't want pay to play and we want what's called open development and not just open source. And I think this is a really important point. So lots of people will say, well, open source has already won a blockchain. And almost every substantial blockchain or distributed ledger has decided, you know, correctly, we think, and I hope you all agree, given that where we are today, that open source is the correct model. So it's hard to find a ledger of blockchain that is an open source. It makes very little sense. If you think about the decentralization perspective, you know, even the mass majority of wallets are open source now. So it's really, you know, becoming a more open ecosystem. But while open source is one, true open development has not yet become the most popular ledger development model. And we think it should be. And we think that open development is the only way to develop a ledger because all of the other methods are centralized to a non-trivial degree. And we'll illustrate that with this sort of, you know, some examples of how open source project types work. So there's what we call the dump and run, which is essentially just a code dump. Somebody throws code. There's no roadmap. It's it's not arbitrary. These are just sort of stuck. There's the open company product, which is sort of, you know, a company essentially open sources of product. But it doesn't allow outside contributions. It does keep a roadmap as regular releases and follows best security practices. There's basically no way for any user to have an impact on the project. Some blockchain open sourcing is this open company product kind of thing. There's also the benevolent open dictator model. So this is what an organization open sources their code. They allow contributions, you know, maybe even to the roadmap from external contributors. But the ultimate authority on merging code and the roadmap and everything belongs to the company. And there's no clear there's no path for anyone that's not in the company to have an impact. On the decision making. And unfortunately, this is what many blockchain companies mean when they say they're fully open source. They're open source, but they're not open development. And finally, the model we like is something we call open development or open governance. And this is where you have a code base with transparently documented and meritocratic governments, which is hosted under, you know, a third party entity. Anyone can join and contribute. There's a clear process for how leadership is decided. And this is generally how Linux Foundation projects work. There's no exception for hyper ledger here. So, you know, with all of these principles, this is what we try to bake into hyper ledger, which is, you know, a global consortium of communities working on blockchain together. So what is hyper ledger, right? It's an open development, not for profit, obviously for blockchain technology with real value. It's hosted by Linux. You know that hyper ledger is neutral and collaborative. It's always open to anyone. I get this asked this question all the time. And we've structured it so we try to remain immune to the commercial interests of any single company. So no single company will ever control hyper ledger. So some background. Hyper ledger is about blockchain software, not blockchains. So we provide a community for blockchain software and tools. We do not run blockchains as part of the hyper ledger foundation. I get asked this all the time, like, you know, where's the hyper ledger blockchain? How can I join? We don't do that. And blockchains are run either through separate entities or foundations. So we have a global team of developers. Anyone can join and contribute and even join a leadership role. And we try to be a transparent as possible. Everything is in the open. Pretty much all our meetings are open, our email lists are all open. There are very few that are not open and the ones that are not open, like, you know, the security response list are not open for a very good reason. There's no pay to play. So you can, like other Linux Foundation projects, you can buy a membership membership in hyper ledger. But it's mostly for community and marketing benefits.  We have a wide variety of blockchain projects. I'll just put that up there. Lots of different applications. And, you know, we have quite a bit of momentum. These are just some numbers. We've had some of the fastest growth of any Linux Foundation project ever. And these numbers indicate it. So so finally, I'll conclude with a question I get a lot, which is how do I pick a ledger platform? This this question happens all the time. And my answer is usually the following. Well, first you need to pick a ledger that satisfies the constraints of your application, right? If the ledger doesn't do what you want it to do, then sort of what's the point? And then pick a ledger that has open governance for its development. You want to pick something that's maximally decentralized. And I hope I've explained why that is a good idea. And finally, I pick based on the community, because a community will have the biggest effect on the ledger's success in the long run. And again, transparency, you know, good communities will show everything. So this is, you know, that's the Linux Foundation analytics statistics. Have people here familiar with LFX? If you all used it before. Awesome. So, yeah, you can see all of our contributor statistics. You can find out who's working in the community, where the company's from, you know, all this stuff. It's open, you know, we're transparent, so it's all there. So yeah, thanks. I will say that if you're interested, we have our global forum in September in Dublin. I think it'll be an exciting event and a good program. So if you're interested in blockchain and open blockchain, it's a great thing to go to. If you're interested, you want to join our community, you can ask questions on our discord. And yeah, thanks. That's it. And I'd like to answer any questions. Are there any questions to provide what? So the question, if I understand correctly, is are there any commercial entities that provide services for a Hyperledger Foundation projects or software? And the answer is, yes, of course, there are tons of companies that do that. We have, I think, one hundred and eighty member companies. And I would say probably most of them do that. And there are even companies that aren't members that do that. So I think that's a very popular business model around Hyperledger. So the question was, who are the top three companies? And I guess that my response is, well, how do you want to measure? So I don't know the internal company numbers, and they usually don't tell us. So so this is a hard question for me to answer. I can answer, you know, what companies contribute the most code or, you know, who are most involved in the community. But it's very hard for me to say, you know, who does the most outside stuff because they they don't tell me that. So by a number of like maintainers and contributors, I believe our largest our largest contributor companies are IBM, Consensus and Accenture. That I could be wrong, but I think that's true. And we could look up on we could spend five minutes on LFX and find out exactly. Great question. As a cryptographer, I always love to hear questions about cryptography. And the question was about zero knowledge proofs. Do we have do we have anything around that? So the answer is, yes, our identity projects heavily rely on zero knowledge proofs. So we have some basic zero knowledge code in our Aries Indy Ursa stack. So the actual zero knowledge protocols are an Ursa, which is just a cryptography library. And they're typically called in Aries, which is our wallet library. And the Indy is sort of the blockchain layer for that. We actually have a big PR outstanding in Ursa that has sort of gotten delayed due to the pride. The whole project is doing a big refactoring. But it's about a ZK interface style of protocol where you can write. You can write, you know, zero knowledge proofs and then have them. You have to write them in R1CS if you're familiar with that, which is a bit complicated. But you can write an R1CS statement and compile it down to a number of different ZK proof systems. And I guess that's the extent a lot of our big. So I base you and fabric, for instance, don't have any ZK piece inherently built into them, you know, but you could certainly build on top of them. The what? The CBDC. Yeah, so that's a really interesting topic. And while hyperledger is involved in a lot of people in hyperledger are working on CBDCs and the hyperledger community, you know, people are using it in the outside community. There's been a big announcement. I don't know if you saw there's an announcement between hyperledger Finos, which is a sister Linux Foundation company and the digital dollar program about an effort to investigate and potentially build CBDC software. So if that's something you're interested, I would highly look up that and I would recommend looking up that announcement. There are a bunch of links in there where you can sort of get started and learn all about the CBDC stuff because it really cuts across a lot of different groups in the Linux Foundation. I would love to answer your question, but I think we're out of time. And if you catch me, I will hang around after the talk and you're more than welcome to ask questions. So yeah, thanks everybody for attending and I hope you have a great rest of your conference. Thank you.


Why is English for specific purposes as a methodology so effective? In 1945, globalization boomed and developing countries in Europe and Africa were quickly realizing that to become technologically advanced, English was the language to pursue as it was establishing itself as the international technological language. The first textbook to be published to educate students in a specified field of English was the structure of technical English, which opened the door to the development of textbooks based on register analysis. Language for specific purposes and English for specific purposes. Strevins described the phenomenon of teaching language for specific purposes as fundamentally dependent on the purpose of the learner, restricting the learner's agenda and in theory inherently making the content relevant and the student motivated. As the idea is a field of language education spread and even to more modern-day thinking, there has been much expressed need to research and develop the idea of LSP, particularly English for specific purposes as it was the major consumer market. Initially there were criticisms of the developing methodology. Register analysis was limited to sentence level, textbooks were lacking in vocabulary and grammar, reading passages lacked authenticity, and form took precedence over function when considering the structure of the content. Some were questioning the point to which registers could be clearly distinguished. As discourse analysis and the descriptions of genres or registers continued to be refined in the field of applied linguistics, many of the rough edges highlighted by the criticisms began to smooth out. The emergence of speech act theory and functional linguistics contributed as well to the shift in focus of LSP's language use, building upon a premise that meaning is produced in the performance of communicative acts. Development of special methodologies. Though the idea of different registers and discourses in language use has helped to propagate a need for ESP. Hutchinson and Waters asserted that rather than trying to develop many differing register analyzes based on scientific or technological field, it would be better to approach ESP from an ideal of a common core. This idea would then influence the ESP practitioner to teach the language from a viewpoint, that the structures being taught are more versatile, than merely the specific register that is being focused on, and give opportunities for teaching to expand past the limits of the register in question. Eventually many different scholars had their own description and theory for how LSB, and by proxy ESP should look like. The major overreaching commonality is that the learner's needs must be central to the development and procedure of the course. Also heavily supported is the use of needs analysis. Not all agree on the method and frequency, but the idea that each student's personal experience and skill set differ to the point, that not only is a needs analysis consistently considered crucial for the success of ESP, but also creates the challenge of meeting the needs of a classroom full of students with varying needs. Another accompanying challenge is that of making a base curriculum, that can benefit society but still be flexible enough to meet the needs of an individual, which is why many ESP practitioners don't use a set curriculum. Do you want to teach English abroad? Take a TEFL course today. Of all its criticisms and advantages, the central benefit of the ESP approach is that it seeks to make the information taught, and the skills gained relevant outside of the classroom. This is not a foreign idea for teaching in general. What teacher doesn't want their teaching to be used constructively and realistically outside the classroom? Practitioners of ESP would do well to think broader than those of Susalawati, in saying that LSB is only for adults and those with higher levels of education. Cruz had already shown how younger learners could benefit from it, and there is the reason to believe that even younger ages than he mentioned could benefit from it as well. One aspect of LSB that can influence any pedagogy, is that teaching needs to be for a purpose, and if the student doesn't realize a purpose, learning will be significantly inhibited. Tips for getting certified to teach English abroad and online


And now that they also can go out and work and earn the money, so why do they need you actually? Or for what use are you? My name is Tarun, I'm 34, I'm from Delhi. Fortunately very much settled professionally in my career, but not settled in personally. I'm married in 80 years, I have a daughter of 4 years at old. The problem is me and my wife both are working, both are having ego clashes. We don't understand each other. The problem is on the heat of fight, I lose my patience and I'm in anger, I'm very much in anger. Even she said that she wanted to be a live apart. I know my mistakes, I wanted to change myself, but she's not realizing what needs to be changed from her side as well. Indian society has not as yet geared itself to the single family, you know single unit family. It's a society of joint families where all these energies were sort of caught in the net of the family and evened out. Society doesn't know actually how to live in this imported style. So that learning process can be very painful and very hard when both the parents are working and earning well so that they can buy all the things which they don't need. And work for those people who are anyway not bothered about them. The result is that they stop to care for each other. They don't have time to do that and often it is in the area of sexuality. And when it's in the area of sexuality and when there is not enough of sexual exchange, there's also a lot of anger. So that's something to address. On the one hand, you do have to start living more from the truth. And she as well. But there is also a certain reality about the whole sexuality. Because if there is no sexuality in a relationship, generally there will be a lot of anger. And especially from the women, more from the women than from the men. So the one hand to look at that whole aspect of sexuality between you and your wife. And on the other hand to look at yourself and try to quiet yourself down by actually trying to feel your Atman, you know, go there. Try to feel that. When your week goes, you get up in the morning, you go to work, you come back in the evening. You have half an hour with your child, then there's dinner and there's bedtime. So then there's no time for each other. You know in earlier times, 50 years ago, 100 years ago, people had very extreme sexual relationships because they didn't have all the other entertainment. That was the entertainment. And so there was less anger.  So that's one side of it. And the other side is, do you want to take up a sadhana or a practice? As you mentioned about the sexuality between us, I mean, even I was the person who was always ready and always forward for doing all these things. I mean, just hugging her or to be close with her so that, I mean, the normal day-to-day routine should not be like that. Wake up and do the office work, do the breakfast and just ready the daughter and just send to the school. But she just need to follow normal routine. Yes, it is sometimes a difficult balance, you know, because women, women, not all, but they like to be around men who are strong decision makers. Females in general don't want to make decisions, but they push their way through because they're not transformed. They haven't understood how to deal with men and they push their way through. And if the man gives in, then they attack. That's the pattern. It's not easy to be a man in today's day and age. It's quite a challenge. But if you start to do this sadhana, this practice, at least 10 times a day, you try to pull yourself to this moment and try to feel You have to ask that question and try to act from that. And what that does is it just makes you stronger and tougher to handle a very tough woman because generally in the Indian subcontinent women have been very tough. They've run the whole story from the back, you know. And now that they also can go out and work and earn the money, so why do they need you actually? Of what use are you?  You have to make a very clear presence as a man because increasingly men are They are becoming redundant for women unless they are very tough and they take over the decision-making challenges because women in general don't like to make decisions. They have problems making decisions. They're not meant to make decisions. They have to offer the male the chance to decide. They decide anyway what they want, but they have to hear it from him. So it's a dance, it's a lila, and if you are in tune with yourself, then you know where to be tough and where not to be tough. A woman will treat a man like that because he's not tough enough. He doesn't keep her in line. And this is not a sexist thing I'm saying here. It's very creative and positive. Tell me what use is a man if he's not able to take decisions, if he's not tough and if he doesn't draw a line. You don't have to hit and shout and things like that. You just have to be centered. But are you centered? No. Why are you not centered? What do you do in terms of your spiritual practices? Nothing. A little bit of meditation on Sundays. If you are tough and centered, then she will back off, which is what she has to do now. What do you do for dharma? You go to the temple once a month, right? Once a week. Once a week. Oh. And you do an arthi and come home. Not even that, probably. A little bit of quick namaskar and then go. How much dakshina dhan do you make every month out of your salary? My mom told me to put at least 5% or 10% of salary in one of the box, which is near to my… But you don't do that? Yeah. I used to forget every time. In the past, in the Indian subcontinent, when there was that strength in the population, it was because they… income was divided into five parts. One part was for dharma, which was the temples and the gurus. One part was for the children. One part was for the parents. One part was for daily life and one part was for savings. How many people give anything for dharma? How do you expect to get strength to live if you don't invest in the dharma? That is something you have to do. You have to do your spiritual practices. You do your spiritual practices. You don't do anything. And then you don't want everything to happen. Dharma, dhan, dakshina, seva, sadhana. Will you do it? Or you want to earn some more money than before? Tell me. I can do that. You'll see how things change if you take it up. It's a decision to live life like that. What are you going to teach your daughter to be a slave of the corporations? What dharma are you teaching your daughter? Nothing. You understand what I am saying? There are millions of men and women like you who have lost all connection with what it means to live with some degree of equanimity and some peace. They are all fighting, you are not the only one. Every house in your building they are fighting and they are separating and divorcing and the children are somewhere and mother is here and the father is here. If you take up dharma, if you take up dhan, dakshina, if you take up seva, you take up sadhana, these are the fundamental pillars of Bharat Varsh.  Nobody tells you anything, you have to figure it out. Yes or no? Yes. Where is your kula guru? What is that? I don't know what a kula guru is, you don't know. Who is your kula devta? I'll have to ask my grandmother. Your kula devta is McDonald's now. Ronald McDonald, that is also part of life. I'm not saying that's a bad thing and it's evil. It's also part of, but it's not the kula devta. This sub-continent, this Bharat Varsh has to wake up. You'll have to start living at least 10% of a dharmic life. That is why you have all these problems and there is no resolution. She will separate, you will separate. That child will grow up without the parents. That child will be traumatized like so many of the westerners sitting here, to whom it happened in the last generation. They're traumatized, they grew up without the father or without the mother and there were fights and this is not something known in this place. This is not only you. I'm speaking to that whole generation in this sub-continent and also around the world. There's no family to push you together after a while. Everyone is like, I want to buy a fridge right now. I want to buy a car, I don't have time. They will solve the problem themselves. That's what everyone says. So take up the seva, take up the sadhana. Take it up, do it. Find the time to do it. Don't use the time to be on Netflix.  This is the rules of the house. We do this sadhana, we do this seva, we do... What are we teaching our daughter? Does she know anything about dharma? Maybe she reads an Amarjitra Katha once in a month and she knows everything about western history and about how to multiply 20,000 times 30,000 when she's three months old. That she knows but it's of no use. It doesn't give a sense of solidity to life and a sense of meaning. That is what dharma is. Dharma gives a sense of meaning. Upholding the dharma. Everyone can do it. It's a non-religious thing. Whatever your religion is, doesn't really matter. You probably don't have one.  So then you don't have a religion. Take that up. It's like a new life will unfold for you. Try to practice. Make a dahan, make a dakshina. When you give energy into something you will get it back, otherwise you won't. How? Do seva whenever you can do something. Keep your working hours minimal. Keep your hours of sadhana more. That's how you bring peace into your family. Your wife will start to respect you. You can go and talk to any guru in the world. They will not be able to say anything else. That's what they'll say. Or I mean I can tell you take this coin and keep it with you. You're the third person I've given it to. I have six hundred of them. Keep it with you and remember now you have got something but you also have to start giving.  You just be miserable. The same story goes on. It just goes on. You are supposed to uphold the dharma. What are you doing for that? Nothing. That's why you're miserable. And then you will go to a psychologist and they'll give you some tablets and then you'll feel all happy for two days after that, even worse. It all doesn't work. What works is taking up that self-realization process and living with it. That is what the dharma life is.


Hello everyone, welcome to the next lecture in the course remote sensing principles and applications. We are discussing about the concept of LIDAR and in the last two lectures we discussed about what LIDAR is, how LIDAR system operates from terrestrial platform, aerial platform which can be extended to space-borne platform also. Then we discussed about like discrete waveform LIDAR, full waveform LIDAR and so on. In this lecture we will continue ahead with the topic. So, in the last lecture I described about having like a discrete return or a full waveform return. Discrete return can store maybe 1, 2, 3, some discrete number of returns, it will not store the entire waveform or the signal that is coming back after getting back scattered from the ground elements whereas a full waveform LIDAR will be able to store the maximum amount of information that comes back from the ground. Hence for certain applications especially dealing with like vegetation monitoring and all, the full waveform LIDAR is often used because of its ability to capture the all the most of the features present underneath the canopy. The next important concept that we are going to see is the effect of footprint of LIDAR. So, footprint we have already discussed, a footprint is like kind of the production of the laser beam onto the ground, how much ground area the laser beam covers. So, essentially the returns within each footprint will be going back towards the target and it will be saved at least some of them will be saved. So, each footprint provides us like valuable information about the terrain or whatever features present on the terrain. So, the footprint size is going to influence what features we record and what we store. So, in the initial lecture about the topic I told you that in order to properly capture the terrain we need to have kind of like a large number of footprints. So, like because each footprint will be giving us like 1x y and maybe like multiple z values associated with it. So, if we have like a large number of footprint we may get proper information about the topography. We may also think that having a large number of small footprints may be of real help to us. Yes, that is of real help to us. That is if you have like a large area, if you have like kind of like a topography, this is like x dimension and y dimension, there are like lot of features present here. So, if you have many number of small small small footprints we are going to get we will not naturally think that we will get accurate information about the x y z feature present within a terrain. Say the footprint sizes say in order of like 1 meter or 2 meter. So, even if there is like a large tree that will be captured properly within that like 1 meter footprint like say the foot tree may be standing like this. Say a footprint may be falling within a tree here and the next footprint may be falling like this and the next footprint may be falling like this and so on. So, the single tree is captured in like multiple footprints which may help us to capture the terrain actually like properly that is what naturally we will think. That is also true in most of the cases for like topographic surveying purposes people naturally go for like small footprint LiDAR in order to have like a small footprint plus a dense point cloud kind of like LiDAR especially for topographic applications. But sometimes it may give us some false information to us, false information in the sense say if you are like collecting data over like a forest. So, this kind of like small footprint LiDAR say in the order of like a meter or less than that may actually miss the tree tops properly say an example is kind of given here say this is like a small footprint LiDAR. Say let us say the small footprint LiDAR is seeing here and the next footprint is seeing here. So, what exactly are we capturing? First thing we are missing the tree top. Second thing is this small footprint is going to capture this leaf this stem another stem and so on. So, maybe some return from here. Let us say this is like a discrete return LiDAR system it is going to store only the first three returns if that is the case this will be stored this will be stored and this will be stored. Actually the ground data is going to be missed. So, because of the small footprint we are actually missing like the tree top because the first footprint is here and the second footprint is here missing the tree top and also being like discrete return we are also missing the ground. So, all these things being like a discrete system or having like a small footprint is going to change the way in which we are going to collect information about the ground. But let us think in another form let us say we have like a large footprint system say in the order of tens of meters say 20 meter system 20 meter footprint. If that is the case then the entire tree may be covered properly or even like a group of trees may be covered the example is given in this figure B. So, the group of trees is covered and it is kind of we are getting we will be getting information from the tree top because the entire thing is covered in one footprint. So, definitely the tree top would have been captured this is there this information will be there and this information will be there because on a whole if you combine like what to say the entire thing the maximum returns comes from this. So, having like a larger footprint will essentially capture the overall canopy structure it may not miss the tree tops and all. So, it is always for certain applications it is beneficial to have like a large footprint ladder.  And also as I told here like having like a discrete and full waveform return is further going to influence the information we are going to collect. So, the effect of footprint may actually give us or may remove some information that we are actually that we want to get. Say another example for like the footprint of ladder is given in this slide. Say here it is like you are having a bunch of trees with like a small lidar system is looking at it. Say let us say we have like many small footprints say here there is one footprint here there is one here there is one and so on. So, for this particular tree essentially if we want to capture the entire tree then we may need to get this information like the tree top and maybe like one or two side elements maybe here or here somewhere. So, that we will be able to characterize this is how the tree looks. Sorry if you look from the top you may have like three returns this is from the top with high elevation relatively higher elevation these two from the sides. So, this is in the top view. But a small footprint lidar system may actually miss the top of the tree may take measurements here or in certain cases for certain large trees it may take multiple measurements over like the same tree. So, either we can miss the tree tops which may actually force us or give us kind of like a sense that the elevation of the tree can appear slightly reduced. Say you have like hundreds of trees if you miss like the tree tops in at least like say 50 or 60 trees within that 100 we are naturally going to get like a false information or we are going to miss the actual height of the canopy. Say this is how it may look you have many number of points say actually this is like the points connecting all the tree tops let us assume this particular line what I have drawn here. But let us say our lidar system is missing at least 50 60 percent of tree tops then what it may give us is it may give us some line like this say the interpolated points may be lying here that is some of the tree tops we are actually missing without even collecting the data which may give us the topography that the canopy structure is highly undulating with lot of like large trees and small trees interposed with among each other such kind of picture we may get.  And also certain as I told certain large trees we may count like more than one return. So, if at all I told you like even we can count the number of trees over certain areas using like lidar we may like have like a wrong count of the trees in such circumstances. So, the footprint of the lidar and whatever the returns coming in from that particular footprint is effectively going to influence the way we are going to observe the terrain or see the terrain. So, this is really important we need to have kind of like a feel for this or understand the concept. So, not all the points which are like in the first return I told you like if at all you are talking about like a discrete lidar system we can separate the first it all the first return separately second return separately last return separately and so on. So, essentially for like a discrete return system especially with like a small footprint all the first returns may not come from the tree top or building top and so on. It can be captured on either sides or similarly in kind of like a large footprint system it is not necessarily bad a large footprint system can effectively average at least in the kind of like an average way it may bring out like the topography to us. So, based on our needs and applications we need to decide which laser system we have to use a discrete form or like a full waveform lidar what should be the size of footprint that we may need and so on. So, essentially we have to choose based on the applications for which we are going to use lidar system. In addition to giving information about elevation lidar will also store the intensity or the power that is returning back from the ground surface. So, even if there is like a canopy whatever is like reflected from the canopy will be the power will be recorded back by the sensor and that is again is really useful to get more information about the terrain. In the initial lecture I told you that generally we use green wavelength or NAR wavelength for the lasers in lidar system 532 nanometers or 1064 nanometers. If that is the case then let us talk let us talk in terms of like NAR based lidar system. We all know that in NAR wavelengths vegetation will have like a very high reflectance. Similarly, like even soil surfaces has typically higher reflectance or naturally land surface has higher reflectance water bodies has lower reflectance and so on right. But vegetation or this kind of relationship between optical remote sensing and lidar sensing is not really direct that is we cannot always imagine if there is some vegetation present on the ground in lidar intensity image also it will appear very bright. Normally in NAR band image our normal image it will appear very bright because of high reflectance. But in lidar intensity it need not be the case. An example is given in this particular slide. Say in the figure A what we have is like the lidar last written elevation. So, it is giving information about like elevation of different points. So, it is interpolated. I told you that whenever we have like a large number of points the points will be kind of interpolated to give you like a surface because we naturally earth is kind of like a surface not a collection of points. So, essentially we interpolate the points to produce a surface. We can identify trees here. So, these are all some high elevation points. So, bright appearance and elevation map is like high points with higher elevation all these things. Looking at the intensity this is like the intensity that is you can think it off in terms of like the power returned. So, from the return power and also like some other information we can sense here there is like vegetation. This is like again this is like vegetation portion and so on. So, again these are like grass here. But if you look at it the trees which will have like a very high reflectance in NIR portion is actually appearing dark than in between barren surface or open surface. Naturally we expect vegetation to have very bright reflectance than soil surface. But here trees has lesser reflectance actually the grass identified as this particular boxy has a higher reflectance and so on. Why is this happening? Why trees appear actually dark? Trees should naturally appear bright in NIR images. It has a very high reflectance. True it has very high reflectance. But we also need to look at the nature of reflection or nature of scattering happening in the terrain element like in the earlier classes we discussed that reflection can be happening from the surface scattering or it can happen from within like the volume within the terrain feature which we call like volume scattering basically. So, if you have like a large tree there will be like plenty of gaps in between. So, the lidar pulse may penetrate into it and multiple scattering will happen from different different portions of canopy naturally right. It is not only like the one either top portion reflects everything. Some light will always penetrate especially like NIR we have seen that it penetrates through the leaves to certain extent and we also know this additive reflectance property because of the penetration. So, what essentially will happen is lidar is essentially like a backscattering observing system. If the sensor is here essentially the signal should come towards it in kind of like a straight direction for the sensor to record it. When volume scattering happens within the canopy the reflected signal need not only go in the direction of incoming beam it can also go in all other directions because it may became more diffuse in nature rather than being like okay wave is coming like this it need not only go back specularly in this direction from towards nadir and towards zenith it need not be like this. When volume scattering happens it will become diffused and a large fraction of energy will be scattered in all other directions and only like a small portion will go back in the same direction from which like energy came.  So, the backscattering is essentially like a small component whereas energy is now actually being scattered into several directions surrounding it. So, that is the reason vegetation appears dark but rather than appearing backscattering if you have like you have like a normal NIR sensor which may see all the information going in certain direction like within the IFOV then it will be able to capture like a some amount of larger signal coming in from the vegetation that is the thing. And also like grass appearing brighter means here in this figure labeled as C so, grass surface naturally there is not producing lot of volume reflection most of it happening within the surface. So, essentially what is coming in from the zenith is going back towards the zenith like this. So, that is like the difference between a normal optical remote sensing system and LiDAR system. So, there is no one to one correspondence between them. We cannot interpret the LiDAR intensity images similarly what we do with the normal images we need to say some caution the patterns may differ but essentially LiDAR intensity provides us additional information rather than just looking at x ways at points if we have the additional information of what is the power return it is really helpful to us it will help us to know what is there on the surface to like a very good extent. But still we need to exercise some caution while interpreting such images. Till now we are discussing about like the general properties of LiDAR systems and in the course like remote sensing course what we are dealing with essentially deals with satellite based remote sensing. So, essentially since we are talking about LiDAR it is necessary for us to know if there are any space based or satellite based LiDAR systems. Yes, there are few LiDAR systems that are there in the space operating from space based platforms. Like in earlier like from the year 2003 there was a satellite called ISAT with the LiDAR instrument called GLAS which was in orbit up to 2009 for measuring the topography of poles, ice sheets, glacier and all. So, that is why it is called like ISAT it is major application is to collect topographic information especially about the glaciers, ice sheets and also about like world's forest. This is one of like the very first space based or satellite based LiDAR system. Now, we have two LiDAR systems operational at the time of recording we have like two operational LiDAR systems in space one is ISAT 2 with an advanced laser altimeter system like called ATLAS advanced topographic laser altimeter system which is there which is developed version of like the glass which is like much more developed version of the glass system glass sensor that was there in the earlier ISAT 1 satellite. So, ISAT 2 again has major aim of measuring the topography of ice sheets glaciers and also like world's forest. See if you look here so the some of the basic characteristics is given here. So, the ISAT 2 satellite has an orbit of around like 500 kilometers like orbital altitude with a laser footprint size of like 17 meters and orbit return period of 91 days. So, Javel just discuss about this. So, the orbital inclination is 92 degrees it is in like a near polar orbit again it uses a green wavelength 532 nanometers because that is like the characteristic wavelength used for studying ice and all. So, it has a swath width of 6 kilometer along the ground track and the type of pulse turn it is called photon counting it is like slightly different from the discrete and full waveform they use what is known as like a photon counting technique. So, this is like one of the operational satellite based LiDAR system that is available. So, this will produce like this will have like a repeat interval of like 91 days. So, once on an average once every 3 months it will collect the topographic information over the same spot on the ground. But why do we have like such a very large number of repeat cycle?  ISAT 2 is not scanner system ISAT 2 produces like multiple beams and each beam will have its own footprint. So, within this each beam the elevation will be stored and actually the swath width is very small. Because of the very small swath width it has to go like large number of orbits in order to cover like a global coverage. Let us say if you have like one orbit like this say in terms of like lamps that you have a swath width of say 185 kilometers. So, within one go you are collecting information about 185 kilometers on either side of your orbit. But let us say now your swath width is just for example, entailing it is just 50 kilometers. So, what essentially happens rather than collecting one full 185 kilometers you are now collecting only 50 kilometers. So, now you have to make at least 3 orbits in order to have like a good coverage even for the same portion right. So, the number of orbits the satellite should make before it covers like the entire globe increases. So, the orbital in the discussions about like the platforms I told you some systems like almost all polar near polar satellites in sun synchronous orbits it will have like a repeativity cycle once every 16 days once every 24 days and all after making certain number of orbits say after making 233 orbits lamp that satellite will return to like the same position again towards the first orbit when it started. So, it is like orbital cycle. ISAT system before it makes completes one full cycle it has to it is it will undergo more than 1300 orbits because of its very narrow swath. The number of orbits it should make in order to cover like the entire globe is extreme large it should undergo 1300 plus orbits in order to cover like the entire globe and hence the revisit time is very large because of its very narrow swath width. So, the swath width and orbital characteristics will define the repeat cycle I told you and also like the repeat cycle swath width will further affect the temporal resolution. So, all these things are interconnected that is why ISAT 2 has like a very long gap between its repeat cycle almost 3 months once. There is another sensor called GEDI GDI which is Global Ecosystem Dynamics Investigation essentially a lidar to map or monitor vegetation in forest. This is not a satellite this sensor is there in the International Space Station which is now housing more number of like remote sensing sensors like GDI is one of the sensors there is another sensor called EcoStress. There are like multiple sensors remote sensing sensors are now being housed in the International Space Station. It is not a satellite we all know it is kind of like space based research observatory which is orbiting in like a lower earth orbit. Say it is not orbiting in terms of like around like 500 to 600 kilometers in elliptical orbit and it is not it will not produce like a global coverage. ISS it has an inclination of about like 51.6 degrees that means it will not cover like the entire large part of globe it will be mostly confined within this 50 degrees to 50 degrees kind of thing. So, that is one of the thing we need to remember. So, G-ray sensors essentially covers forest vegetation in tropics and temperate regions even not even in the like the very high latitude boreal regions. But this is one of like the demonstration system to prove that lidar based remote sensing is really helpful for monitoring the global biomass like the biomass of forest, carbon cycle and so on. Using this height information we will be able to model the biomass and also get information about like the carbon cycle happening within the forest ecosystem. All these things are really vital information in order to understand the earth's climate even like the earth system as a whole. So, the G-ray sensor uses an NAR wavelength swathed with of like 340 kilometers like it is not again it is not like a scanning system not like that it will have like again multiple beams in the across track direction and cover it. So, space based system they are not scanning based systems they have like in individual beams 4 beams 6 beams and all simultaneously it will be covering the ground. And this is like a full waveform lidar as I told like for vegetation monitoring a full wave waveform lidar can be useful and the laser footprint has a size of roughly 25 meters. So, this is the these are like the 2 sensors lidar based sensors that are there in orbit. So, after this G-ray one more sensor called MOLI multi footprint observational lidar and imager is planned to be launched again to be placed in international space station. So, this is kind of like a second demonstration tool like G-ray will be taken off and MOLI will be replaced that is like the information available in the literature and it is planned to be launched in the year like 2021 again it is like a full waveform lidar observing in NAR wave in 1064 nanometers with SWAT with a for like 1000 meters and so on again in ISS. So, these are some of like the some examples of lidar based or satellite or space based lidar systems which provides data ISAT 2 data and G-ray data like publicly available we can download them and use them. So, before we conclude we will just see like few applications of lidar briefly I am not going to explain any case studies and all just going to highlight few applications for which lidar systems can be used. The first major application for which lidar was used is like topographic surveying in order to obtain XYZ of the various features on the earth surface and that is like this major application still being used whenever we want like a high precise or highly accurate digital elevation model like three-dimensional representation of the terrain then lidar is kind of like one of the go-to technologies it will provide really quick accurate and precise digital elevation model and actually like scientists from different organizations led by like IIT Bombay created like the flood map or like the flood forecasting system for Chennai city in which like the DEM was collected from a lidar system because for flood modeling and all or flood forecasting applications we need like a highly accurate and dense DEM. Dense DEM means the spatial resolution has to be like really small it has to be in order of like less than a meter with very high vertical and horizontal accuracy in order to properly model the way in which the flood water may run. So, the lidar system was used to collect the DEM information for that particular project and also for various large scale civil engineering projects lidar system can be used like the high speed railway project between like Mumbai and Hamadabad a lidar system is used to carry out the survey along the path because the survey has to be completed in order of few months within the entire stretch and if we resort to like ground based survey it is going to take us years to cover that 500 600 kilometer stretch. So, people used lidar system and this one of like large scale application of lidar system for engineering purposes and also like as I told lidar based elevation information is also useful for monitoring and modeling global ice sheets glaciers and all like as demonstrated by ISAT satellite normally people will not launch a satellite if some data is not extremely helpful for a certain application launching a satellite is extremely costly. So, from that itself we can infer how important elevation information is for cryospheric applications and also for ecosystem based or especially forest ecosystem based applications we also use lidar system like for understanding forest canopy height estimating biomass and all lidar system is often used. And one more application is bathymetry like in order to map the topography of lakes or water bodies below the water how the topography is like the water surface maybe let us say that we have like a lake let the water surface be this. So, how the topography of this bottom surface lies lidar has been used to map certain in certain bathymetric studies. Most of the bathymetric lidar systems will use both the wavelengths 532 nanometers and 1064 nanometers. So, we all know that NAR wavelength has like extremely low penetration water bodies. So, whatever like the returns we get in NAR wavelength will most likely would have returned from the top of the water surface and green wavelength has certain penetration capacity into the water bodies. So, the last return may might have originated from some features present in the water or sometimes even like the bottom or the bed topography. So, the difference between them between the returns of green band and NAR band will give us information about the bathymetry of that particular water body. So, this is like another application for which lidar system is used. So, essentially lidar is one of like really advanced technology or I will say it is like combination of different technologies combined together will help us to get information about the earth and features on the earth with a much rapid turnaround time. So, with this we end this particular lecture and also this particular topic. So, essentially we have covered almost most of the principles that normally like a new coming students want to know about remote sensing like optical remote sensing like visible NAR wavelengths, how it will interact with earth surface features, thermal infrared remote sensing, their physical bases, passive microwave, active microwave all the basic principles we have discussed about at least to in some detail. So, from the next lecture onwards we will slowly move on to like application part or the analysis part I will say where we will talk we will just briefly get introduced to various data products then we will see like a few analysis and also like few applications in the last few lectures of this particular course. With this we end this lecture. Thank you very much.