Delos is keeping the world company today. We're going to talk about psychology and whether it can explain the Israel-Amos war, because we do need some explanations. And for this discussion, we have Gene Rosenfeld, emeritus, history, religion, terrorism out of UCLA. And we have Tim Apichela. He joins us from somewhere far away, and he is our co-host. Thank you much for being here, both of you. So Gene, can you give us a scope and depth of this discussion? We're talking about psychology here today, and psychology is always a little scary. Yes, and psychology is a word that also covers ideology and religion. So let's keep that in mind. And what Nafiz Hamid from Kings College in the UK has written is extremely insightful and based on his cognitive science background. We're finding out that a lot of the explanation for human behavior in the field of religion and violence and also altruism, by the way, has to do with certain ways in which human beings respond to a particular situation, a particular set of circumstances, that a person with good values, what we consider good values, can do bad things because of this. And the field of social psychology has some famous experiments about this that I'm studying. And Hamid also has done some cognitive science on this too. So what he's saying basically is that what's happening in the minds of Palestinians and Israelis is what is keeping them at war and apart. And he has certain observations from the science end of things that also accord with my field history of religions, which is based on anthropology. So we have come together with quantitative and qualitative analysis to underscore some things that would really impact negotiations if we knew these things and we actually took them into consideration. Basically, what he's saying is that each side has absolutist moral values. And that leads them, in essence, to undercut the human aspect of the other side. Dehumanization is something that occurs. What he calls parochial altruism, where you look at your side and say, we're all good. And you look at the other side and you say they're all bad. We have that in this country too, Jean. In what? In this country, America. It operates in human behavior. These are based on observations and experiments having to do with basic human behavior in different sets of circumstances. When you extract the principles and conclusions from these experiments and apply them to conflict situations on the world stage, they explain a lot and inform you as to how you can go about resolving conflict. That's the end object of all of this science is to be able to resolve conflict. So what has happened is there are competitive, we know there are competing narratives. There are also competitive notions of victimhood. For the Israelis, it goes back to pogroms and holocausts, which was activated by what Hamas did. The memories were activated. And that intensifies the psychology and attitudes of the people. On the Palestinian side, it's the Nakba, the having to flee Jerusalem and flee the part that is now Israel. That's what's happening in Gaza. They're having to flee their homes in Gaza. So that reactivates and intensifies their moral absolutes, their narratives. What happens when you sit down with other parties like Qatar or Egypt or the United States, Hamas to try to resolve these issues is that states like the United States and Qatar and Egypt all look at it from a utilitarian point of view, not a religious or ideological point of view. They look at it and they say, well, we'll give you more money if you do this and so, or we'll reward you this way. What that makes the parties to the dispute feel is not listened to. They get very angry and disgusted. They don't want to hear this. So how do you resolve it if they're both dug into their sides and it has to do with the feeling of collective victimhood and not being heard? You do that by offering symbolic concessions. What is a symbolic concession? It is the Palestinians saying to Israel, okay, we understand your feelings about the Holocaust. We understand what happened to you. We acknowledge that. And for the Israelis to say the Palestinians, we have empathy for what happened to you in 1948 when you fled your homes and now you can't come back. That's the way you start. You address feelings first and then you work out the actual details. That is the essence of Hamid's article and it bears incorporation into any negotiation having to do with ideological conflict. Wow, okay, okay. That's the stage. Tim, your thoughts about that? Is that a valid way to proceed? Yeah, I agree 100% with Jean because you are not going to resolve a 100-year conflict, or a thousand-year conflict, thousands of years conflict until you get to the feelings of both agree parties. And I think a part of that is the acknowledgement that one party has to acknowledge for the other side. And that is they have a shared humanity. I don't even know if you want to call it Maslow's hierarchy of needs, that they have children to raise, they have families to raise, they have the need for security and safety, they have the need for financial well-being and the relationships that are near and dear to them are near and dear to both sides. So there has to be an acknowledgement of shared humanity that one side is not the evil monster that propaganda tends to paint them as. And then I think also a central part of this is the act of contrition. And that is to say, maybe you're not empathetic, but at least is it possible to be sympathetic to the grievances of both sides, one side to the other. Can you have a shared sympathy? Empathy is tough because you have to dive deeper into what empathy is. But then there's the act of contrition to say, yes, we acknowledge that your grievances are valid and you have gone through pain, a lot of pain. And that needs to happen on both sides. And before that happens, you're really not going to get anywhere with negotiations because both parties are aggrieved and they're hurt. And it's not just one individual that's hurt, but it's an entire population. And then the magic of religion is the central tenet of all religions, or most religions, and that is the act of forgiveness. It may be conditional forgiveness, but it's essential to move the negotiations forward. And without conditional forgiveness, I don't care what you talk about. I don't think it's going to hold. Okay. Looks like this is two on one, or one on two.  And so in order to sit at this idyllic table that you guys are both describing, one of the parties has to stop saying he wants to kill us. And that is deeply ingrained. Talk about psychology. Those kids are raised before they can speak to say, let's kill all the Jews from the river to sea and all that. Today there was an article mentioned before the show by Brett Stevens in the New York Times. And he talked about the relevance of the tunnels. And in fact, the Hamas approach to all this. I can't imagine the Hamas, by the way, agreeing not to kill the Jews, and sitting down and being contrite in some way. But Stevens concluded with a really remarkable statement. He said, the fault for every death in this war is on Hamas. And he gave you a complete analysis of that. So the question is, how do you deal with a situation, and I'm not asking you, I'm just raising it rhetorically, how do you deal with a situation where one party is clearly at fault for atrocities that are unforgivable? Can they be excused? Can we forget? Can we forget the Holocaust? Never again, and yet we have again. So I suggest to you that the human condition is flawed. I suggest to you that the way to resolution in all through human history has been through conflict. That's war. And then ultimately, the fellow, the country that prevails, that has the power. And power is an important way to achieve peace. Or maybe it's a result of achieving peace. In any way, I think you need an enloco parentis figure at this table, this hypothetical table of negotiation. Enloco parentis like the United Nations, which has failed, so forget about that, like the United States, which used to be the city on the hill back when, but it has failed in that regard. And I'm not sure that it can be enloco parentis. Who can be enloco parentis? Can religion be enloco parentis? Can it provide the moral compass? I'm not sure that the religions of today are the same. They were 50 years ago, or even 20. Islam is not really held up as a religion of peace. And the terrorists justify their actions and atrocities by Allah, which is in the Quran. So I'm not sure that you can have the negotiation you guys are talking about with due consideration of all the psychological points. It ain't going to work, not practical. Go ahead, Jean, respond to me. Okay, let's go back to some of our very first discussions when this happened on October 7. When I believe I made the point that you have a two-track way to approach Hamas, one is negotiation, the other is war. They have to happen at the same time. Because what happens on the battlefield determines what happens in the negotiations. So that's from the perspective of realism. You also have to frame the war correctly. What conflict does this resemble and how were those conflicts resolved? We're talking about the conflicts that are most like what's happening today in Gaza took place internally in South Africa under apartheid and the resolution of apartheid. And also between the UK and Ireland over many, many years where terrorism and bombings were involved. Those types of conflicts ended with negotiations and reconciliation, particularly in South Africa, where you had a reconciliation committee. You had both sides adhering to moral absolutes as you do here. Both sides had to agree not to punish one another for their attitudes and ideas. We're talking about the people now. We're not talking about the governments. We're not talking about Hamas per se and Hamid is talking about Palestinians here on the West Bank too. And inside Israel, there are many that feel great deal of empathy and sympathy with their cone prayers. So you start with the intractability of moral absolutes and you work from there recognizing that the way you're going to get a concession is not only on the battlefield, but also in recognition of the full dignity and humanity of the other side. You have to stop the dehumanization process while you're in negotiation across the table. That's number one, because it's the dehumanization which excuses the atrocities that more always rises to the level of atrocity of each side. And one way or another, bringing this factor, their ideology, religion, moral absolutism, parochial altruism factors into the negotiations will make the negotiations more effective because right now there have been negotiations all along and there's been war all along. But what's on the table isn't there yet because each side is adhering to an absolutist perspective. But if we look at history and the examples that I've cited, we've seen there are other ways to do this and what Hamid is doing as a basic scientist and what I am doing also as a basic social scientist is trying to point the way in which certain principles can get us further along the road to resolution. I agree that there's a lot of Israelis that are sympathetic and there are polls and there are interviews all over Israel where you can see that the people are kindly. I don't think you can find the same kind of reaction and sympathy when those polls and interviews done on the West Bank doesn't come out the same way. Also, I want to mention before I let Tim loose on this, I want to mention that when we talk about negotiation, at least when I think of negotiation, I think of a table. I think of the parties sitting at a table and looking deeply into the eyes of the authorized people, people who represent the warring factions. Then I think the psychology plays a big role, but first you've got to get them to the table. I don't think the Israelis are going to be so quick to meet with Hamas, the killers of the children, the holders of hostages and the like all this time. I don't think the parties are going to get to a table. If they got to a table, it might be better. Some of these psychological tools, as you say, could be useful. Before that, we have to look at who's winning the war to get to the table. In the first ceasefire, I guess the perception was the Israelis were really beating Hamas up pretty well, and so Hamas came to a kind of proverbial table, but right now there is no table. People, they are suspicious of the proxies who are at the table, if there is a table, and all the vectors that are affecting the communication, if you will, between the parties. Tim, you are our esteemed co-host. Why don't you see if you can come down on one side or the other of this discussion? On one side or the other, that's not going to happen, but I'll tell you one thing. You look at the Irish and the United Kingdom conflict in Belfast, and what really made some enroads into eventual negotiations was a groundswell of mothers who have lost their sons and daughters in the bombings and the shootings for decades in Belfast, and those mothers locked arms with the opposing side of mothers, because both sides agreed to a mutual curl of damage that has taken place on their families and their communities, and it was nothing more embarrassing to see a parade of mothers locked arms with, quote, unquote, the enemy to embarrass the government to say, if we can do it, why can't you? And so with through a ground up disgust of war and carnage and damage and a demand to say, enough is enough, we've lost enough, the past be damned, we have to start from the president and try to move forward to end this conflict, to stop the carnage, to start the collateral damage, and I think sometimes that happens in conflicts. I'm looking at Russia and Chechnya, the mothers of the slain soldiers, the many soldiers killed in Chechnya rose up and they protested to say, enough is enough, we can't change the past, we can't bring our sons and daughters back, but we can do one thing and that is to move forward and to at least have a ceasefire of hostilities and try to live with one another, although there may be borders and walls and militaries on each side of the wall, but at least we can stop the carnage. And I think to Gene's point that it's going to take place on a human level versus a tit for tat negotiations across a wooden table. Well, you know, you kind of make my point, this is a war of attrition in both cases and that means you have to have plenty of war before you get to a negotiated result in Ireland or any war that's been going on for years. It goes to my theory about the stock market, which I've told you before. The stock market goes up until it gets tired of going up. This is the fatigue theory and when it gets tired of going up, it comes down and when it's tired of being down, it comes up again. And it's attrition on both ends of that.  But these negotiations don't happen right away. And my question to you, Gene, is in the article that you are referring to, is there talk about the timeline, about attrition, about fatigue before you get to an appropriate environment for, you know, humankind, human empathetic negotiation? Okay, let's talk about attrition. No, this article doesn't address that because it has a very specific purpose. I'm sure he could address it. He's got extensive creative academic work behind him. But let's go to another analogy that I have used before in studying the battle of Okinawa. The Battle of Okinawa was the last battle against Japan in the Pacific War. It was extremely, it was extremely sanguineous. There was huge casualty rate, particularly on the Japanese side, civilians and army and children. And it was taking place after Japan's major cities had all been bombed to rebel, basically. And the way in which that, quote, war of attrition was heading was toward a military solution. And what was the military solution? After 82 days in Okinawa, the atom bombs were dropped. So it seems to me that if you're being geopolitically realistic, you have to look beyond a military solution in the modern age. Or you're going to wind up with a wider war and a longer war. I don't think if this war goes on too long, it's going to be confined to Israel. And there already are major initiatives right now on the part of other interested parties, as well as Israel, to come to a negotiated solution. That's why we're talking about it today. That's what we're heading toward, if we don't want something that we don't want at all.  And I don't, if you look around at all these players, I really don't think they're rational. I thought Brett Stevens' article in The Times today was a rational kind of analysis of how the Israelis feel. And not inconsistent with, you know, the fellow we love to hate, you know, Netanyahu. But let me throw one more thing in the pile here, Tim. And it's the notion of anticipating a result. Because what Gene's talking about is, hey, if you guys don't come to the table and be kind to each other, we're going to have a much worse situation. You know, it's looking into the ghost of Christmas future. And when you go in litigation, you go before a settlement judge, and the best settlement judge in my time was Ron Moon, bless his memory, he was wonderful. And he would say he would call you in alone. This is the same thing in arbitration and mediation. He would call you in alone and he'd say, hey, don't you understand, you're going to lose. You're going to lose this case. You're going to go to trial and they're going to slam you. And then, of course, he would go to the other guy and alone in his chambers and he would say something similar. Here are the weaknesses of your case. This is what's going to happen to you. We don't have Ron Moon here. He would be an interesting character.  He discourages you thinking that your case is a slam dunk. And by the time he's done with you, you're now left to wonder whether or not you're going to get out of this thing alive or not. Exactly. That's my point. And don't we need that? I'm asking you both. Don't we need that for this to work? We need it in local parentis, somebody who is respected by both sides, who is credible, who is rational, a fair witness person who can speak to both sides and say, come on, you guys. I'm going to be parental here. I'm going to be, what's it, Robert? I'm going to talk about fair witness. Somebody who's not bias in any way. And you really need that from a practical point of view to get the people to the table and to have them get rational. Your thoughts? Well, what ultimately stopped the arms race between the United States and Russia? What was it? It was an acknowledgement that mutual destruction is inevitable, that on nuclear winter, there's no such thing as a limited nuclear war, that all parties lose. And it's not just the United States and Russia, but the entire world loses. And so over time, that acknowledgement, I think, started to take root. And if there's an acknowledgement, as you suggest, that there's future consequences, a future consequence that could be avoided, and the consequence is mutual destruction, complete mutual destruction, then there's a pathway, an alternate pathway, to say, here's an alternative that we can explore, that we can resolve a conflict and reduce our nuclear arms and try to cooperate with one another at a better level. It wasn't just out of the blue that Russia and the United States came up with these nuclear accords. So I like the analogy of Dickens' Christmas past or Christmas future. Are these the things that will happen? Or are these the things that may happen? I don't want to be biased about this, Jane, but I am. How can you tell millions of people who believe it's better to be a martyr?  How can you bring them to the table? It's very hard, even for a guy like Ron Moon, to have influence over them because they are interested in something which is self-destructive. And how do you get them off self-destruction? Jane, I'm going to do something that may make you a little mad, but I have to point out that the attitude and argument that you're making in this discussion validates the experiments on which Amidst and other social psychologists' ideas and my own history of religions field have basically put forth on human nature. And that is to have a moral absolutist position. That one side is better than the other side. Now, just for theoretical purposes, set that on the shelf. Okay? And look upon the other as fully human and just as capable of good and evil as you are, except that you could do what that person did that you hate and that that person could also be as good as you are. That's the big mind change that has to take place because whether or not you acknowledge it, the symbolic, religious, irrational, non-rational aspect of this conflict is what's driving it. That's what Hamid is saying. And that's what the Milgram and Zimbardo found out in their examinations and experiments in the 20th century on why good people do bad things and what underlies conflict and violence. We have to learn from the laboratory and then we have to figure out creative ways to bring those conclusions about human nature into the real world where there is conflict and the parties are all talking to one another and talking past one another. They're saying A, B, C, D, and first, then you can go on to putting down your specific points. First, you have to have an attitude arranged. Well, I'm just realistic. And no, no, I believe that if you went to Israel, you'd find a lot of people that would absolutely agree to sit down and put their their bias aside. Even the Holocaust put it aside, at least for this discussion. That's the practical humane approach. If you went to the West Bank, you wouldn't get that. That wouldn't happen. So it is asymmetrical here. And I'm not sure that you can work with that. How do you get both people, both sides on the same page? Because one side, what would you have done from a moral point of view, a practical point of view, a point of view of avoiding conflict on October 7th when it came with atrocities? Would you have said, Hey, that's okay. We're turning the other cheek. No problem. Oh, let's sit down and work out your problems. I don't think that would have happened or could have happened or should have happened. I have to point out that the hardest part of what I have done over the last 20 or 30 years is talking to people about what I do and to convince them that it's realistic. It's not idealistic. It's not sympathetic to the bad guys. And the hardest part is to make the point that, like it or not, what we have learned is that people behave the same way in the same set of circumstances, no matter how good or bad they think the other guy is or they are. And so it's we're talking about human beings who are in negotiation on the part of the parties that are in conflict. They're individuals who are talking to one another. The head of the Mossad, the head of our CIA are talking to one another. These are the guys we have to convince. These are the guys that we have to show these experiments to. And somehow that has to filter into the discussion. We're not talking about all of the Palestinians or all of Hamas or all of the Israelis or all of Netanyahu or Smotrik or anybody else. We're talking about the individuals whose mission is to get this thing going because I'll give you another example of stalemate. And that is North Korea. We fought a Korean war. We have a truce. That truce has been in place since 1952, I believe. And because it's never been resolved, we now have a nuclear state hostile who's decided that they are still in a hostile situation with South Korea and thereby us also. So you don't just have mutual assured destruction of Hiroshima on one side or the reconciliation of South Africa on the other side. You have the stalemate of North Korea as well. So there are big dogs in this hunt that we need to confront and deal with. And if the lab scientists and the the little academics like me can throw some light on that as to how we talk to one another, basically. So much the better. Let's give it a try. All right, Tim. See what you can do with that. Okay. Let me roll on down the road here with it. You know, I'm going to quote, I'm going to use some of the some of the discussion points from Dr. Joseph Campbell. You guys probably remember him from the PBS series, The Power of Myth. He was a professor at Sarah Lawrence College. That's my view. And guess what? What he said is that when religions acknowledge, regardless of what the religion is, no matter, you know, is the acknowledgement of the divine creator. And when you acknowledge that each individual has an element or a spark of the creator within them, then it's awfully, awfully hard to say my religion is better than yours. You drape that spark of divinity within the individual.  But when you get to the core building block of what religion is, is the acknowledgement of the creator and the creator within us. And so you start from that and you work your way up. And you work your way up. As I suggested at the early part of this program is that everyone has their their need for family and the care family and security. And then you work your way up of acknowledgement of past transgressions against one another. And then you go to the act of contrition, limited contrition, but conditional contrition, but contrition. And then that's where sympathy and empathy come to play. And then ultimately, hopefully, the acknowledgement that there's mutual destruction for both sides. And then let's let's get on hand with a limited forgiveness. Then we can go to negotiate since a point by point of what we trade to settle this conflict. I can imagine just calling Kim Jong-un and say, Hey, come on, stop that. Think it'll work. Think it'll work. You don't do it like that. You don't do it like that.  That's how you start the conversation. Well, we're almost out of time, but Gene, I want to ask you if you could give us some actual steps, okay? Pick any controversy, any conflict. Israel Hamas would be a good way to start. What's the first step forward? The first step forward is to acknowledge that you're heading in the wrong direction and that you both want to find a different way out. And then to ask the other individual, how do you think we can get out of this? And then saying this is how we think we can get out of this. And there won't be agreement. And then the next thing to do is to acknowledge the suffering on the other side. Do you acknowledge they're suffering? Yes. You historically for 75, 80 years have suffered this trauma, and we historically for 135 years have suffered our trauma. And we acknowledge the fact that you're human and that you have dignity and vice versa. Now, just the mere factor of these acknowledgments in the work that Hamid has done has made the parties more likely to listen to one another and to make concessions. Whereas, if they sit down at the table and they just talk about, well, zero-sum game, this is what we want and under only those conditions, and we'll pay you for this or we'll punish you for that, that makes both parties harden, get disgusted and angry. These, dealing with the emotional reality of the situation, where you are, and putting aside what you call the material points or what he calls the material points, just initially will soften the both parties to the point where they can discuss the details better. If you have a big argument with your partner in life, how do you reconcile that argument by acknowledging first off that both sides have a point and both sides are feeling hurt or angry or upset, and they have good reason to do so? In other words, talking not down to that person or treating that person like an object, so it's the same stuff in bigger conflicts. Well, it's a change-up. It's a question of how to get there. It's a change-up. You're talking about, wait, wait, I got a new idea. Let me express the new idea, and this is an idea which you may like, or at least you won't hate as much as before. But who does it? Does Tony Blinken get on the phone? Does Netanyahu get on the phone? Does the third party? Is Qatar involved? Is Egypt involved or Jordan or Turkey involved? Who actually opens the olive branch? All of these parties are involved right now, and they're talking to one another in very complicated fashion. I mean, like I said, the two heads of Assad and CIA are talking to one another. Blinken's talking to Netanyahu. Egypt is talking to Qatar. I don't know the details, but it is not terribly organized, but it's more organized than what's happening on the ground. So leave that to the parties. If they adopt the conclusions that are well-founded and replicated, have been replicated for years in terms of how people operate in violent situations, if they can accept the basic findings of that incorporated into how they negotiate with one another no matter who's talking to whom, you're going to get a little bit further along. The alternatives are not great. We here certainly agree, and by the way, I want to be clear. I am not angry with you or anything you say. I could never ever be angry with you or anything you say. But Tim, why don't you summarize and try to wrap around this and explain to our viewers where we have gotten today? Well, Jay, I agree wholeheartedly with Gene that if you're going to resolve a conflict, you can't do a position-based conflict. You have to use an interest-based format of negotiation, and that is acknowledging the humanity. It's acknowledging the grievance. It's acknowledging the reconciliation. It's all the things that you do, as Gene suggested, or stated that you do with your spouse or your significant other. You don't begin to resolve the matter without doing that first. And so I have to run, but Gene has my vote. Sorry, Jay, and I'll leave it at that. We're going to close the show. Thank you both very much, and I will all be calling Netanyahu Senwar and explaining this, and maybe they'll take our calls. Thank you very much, you guys.


Hello. I'm Stacey. I'm a GIS analyst with the Natural Capital Project, and I'm glad that you've joined me to learn some techniques for working with the geospatial data that's used by the Invest Ecosystem Services Modeling Toolkit. This episode provides an introduction to working with digital elevation models. To get the most out of this tutorial, I highly recommend following along in your own GIS session. In this video, we will demonstrate techniques in QGIS, and we'll be working with some sample data. And that sample data is linked to on the webpage for this video. In several previous episodes, we worked with data in Nepal, so we will continue with that location in this video. If you happen to have a QGIS session saved from those earlier episodes, then you can use it again now. If you don't, that's totally fine too. You can just open up a new session. So if you haven't already, now is a good time to pause this video, download the sample data, unzip it, and bring up a QGIS session before continuing. A digital elevation model, or DEM, is a raster with an elevation value for each pixel. A DEM is required by the freshwater models NDR or nutrient, SDR or sediment, and seasonal water yield. And for these models, it's very important that the DEM represent the areas hydrology correctly. Coastal vulnerability also requires a DEM, but it's not as important to get the hydrology correct for that model. Now a DEM can be obtained from many different sources. And often these sources have global data coverage like NASA or hydrogens. If you compare multiple DEMs in the same location, you'll find that each one is different, some more accurate than others in that particular place. Then if you look at a different location, you may find that some other DEM is more accurate. So they are highly variable. But one thing that is pretty much guaranteed is that none are perfect. I have never found a DEM that perfectly matches a real-world stream network, and many don't even come close. So be aware that you may need to try several different DEMs before finding one that works well enough for your purposes. Regardless of the DEM that you decide on, you'll probably need to do several steps of preparation before it's ready to be used with an investment model. These steps include merging raw DEM data into a mosaic, checking for holes or missing data, projecting to whatever you've selected for your analysis coordinate system, filling sinks, verifying the stream network, and creating watersheds. In this tutorial, we will work through the first four of these steps. And to keep each episode from being too long, we'll cover next steps like creating the stream network and watersheds in separate videos. Along with this video, the Invest User Guide has a section called Working with the DEM, which provides an overview of the different steps involved, as well as the methods and GIS tools that can be used. A link to that User Guide chapter is included in this video's webpage. All right, let's go to a GIS session and work through some of these steps. Open a file explorer window to the folder containing our sample data. It's called Preparing the DEM data. And inside of this folder are five rasters with Aster G DEM data, which I downloaded from NASA, the US Space Agency, which provides several global DEM products. Let's drag and drop all of these into the GIS. Because DEM data can be pretty large, it is often broken up into smaller tiles. And so often, we need to download multiple tiles to cover our study area. In this case, we need five tiles to cover the whole watershed that we're modeling. Because the Invest models require just a single DEM raster as input, we'll need to combine these tiles into one raster. To do this, we'll use the Merge tool. So we'll go to Raster, Miscellaneous, and we'll open up the Merge tool. For input layers, click in this box to the right of the window, and then click the Select All button. To go back to the original window, we'll go up here to the left and click on this blue button. For output data type, we need to choose the same type that the input rasters have. So right-click on one of the tiles. It doesn't matter which one. And select Properties. And then click on the Information button. Looking at the data type value, we see that it is a 16-bit signed integer. So that's what we need to use for the tool. So back in the tool under Output Data Type, we will select Int 16. All right, under Advanced Parameters, the first one says the input value to treat as no data. From reading the Aster GDEM documentation, which is included in our sample data, I learned that they used a value of minus 9999 for what they call void pixels. So we'll specify that same value of minus 9999. The next input is Assigned Specified No Data Value to Output. Now, it is important that we do set a no data value for all rasters that are used in Invest. The model itself doesn't really care what the actual no data value is. But if no value is set, it can cause errors in Invest, which are often hard to diagnose. The only thing that we want to make sure is that whatever value we choose, it is not actually valid elevation data. Now, I have to admit that I've had a hard time getting QGIS to handle no data correctly. But one thing that seems to work in this moment is to set the no data value to minus 32768. And that is the maximum negative value for an Int 16 raster. So our no data, the input pixel value to treat as no data, is minus 9999. And the output no data value is minus 32768. All right. So now if we go down some more, this entry called merge is where we specify the output filename. Click the button to the right of the entry and say save to file. Navigate to the folder where you want to save your tutorial data. I'm going to save mine in the same place where I have the sample data. And I'm going to create a new output folder there. So I'm going to do a new folder and I'm just going to call it dem underscore output. And I'm going to go inside of this folder and create the output filename dem underscore mosaic.tif. And I do recommend using TIFF files for your rasters and invest. All right. So click save. And now we can click run. All right. Now we have a stitched together dem raster. If we turn this on and off, we can see how we no longer have these edges. Very obvious, like we do in the original tiles, right? The edges seem to have been stitched together correctly. But then we notice that the minimum and maximum elevation values don't really correspond very well with the min and max values of the tiles. This is because of how QGIS symbolizes rasters by default. So let's right click the merged raster and select properties. And then click on symbology. All right. What we need to do is click on the min, max value settings. And at the top here, make sure that min, max is selected, like mine is. The statistics extent should be whole raster. And then the accuracy should be actual. And click OK. And you see how the numbers have changed. Now they correspond much better to the minimum and maximum values that we find in the tiles. One thing that's worth doing at this point, and this is what we would do in real life, is to make sure that there are no holes or areas of missing data in the map. Unfortunately, I haven't found an easy way to do this in QGIS. So I'm going to leave this as an exercise for you to figure out. One way to do it would be to create a background of very bright pixels so that you can see, and it's highlighted, where any missing data might be. Now if we do find no data values within the study area, then we need to consider how to fill them. And since having holes can cause problems with the hydrology models, sometimes it causes them to throw an error. And even if there is not an error, the missing data will interrupt the flow path in that part of the watershed, leading to incorrect results. And working with data holes is a whole other world that we won't get into now, since it's not required very often. But you can get ideas for how to deal with them by reading the user guide section, working with the DEM. All right, the next step is to reproject the mosaic DEM to have the same projected coordinate system that we're using for our analysis. In QGIS, reprojecting is done using the warp tool. So let's open that by going to raster, projections, and warp. The input raster is the mosaic DEM that we just created, which I call DEM mosaic.tif. So make sure that that is selected. Now the tool will automatically detect the source CRS for us, and CRS stands for coordinate reference system. So we don't need to specify that. But we do need to choose the target CRS. Now let's click in the box to the right of this entry. Now at the top of this window, let's uncheck this box that says no CRS, because we want the rest of this window to be active. We talked about coordinate systems in a previous episode. So suffice to say that it's up to you to choose the projected coordinate system that you'll use for your project, and make sure that all of your spatial data uses it. One very standard system is UTM, and that's what we'll use now. Now our study area in Nepal is in UTM zone 45 North. So one easy way to find this is to type this into the filter bar at the top of the window. UTM zone 45N. Now down here below, a list of values will appear with several options to choose from. Now if we scroll down, we actually want the last one in the list, this WGS84 UTM zone 45 North. If we click on that, it will show a map of where that UTM zone is in the world, which looks about right, and that's a very cool feature of Q. So let's click OK to close that window. Next we'll choose the resampling method to use. In this case, it is very important to select a different resampling method. By default, the tool will use Nearest Neighbor Resampling, and that works great for categorical data like land use, and it can be used in many cases, but it should not be used for resampling DEM data. If you resample with Nearest Neighbor, the hydrology layers that are derived from the DEM, like flow direction and flow accumulation, will probably have a weird grid pattern to them that is very incorrect, and it leads to the creation of bad flow patterns, bad streams, and bad model output. So I usually use bilinear, and I'm going to select that now, but cubic also works. You're also free to try out any of these other options, but I have found bilinear and cubic to work the best for me. But we'll choose bilinear right now, and this time the tool will automatically detect our no data value, so we don't need to specify that. If we scroll down, we do need to specify the output file resolution, which will be given in meters. From reading the Astro G DEM documentation, which is included in the sample data, I know that the data resolution is 30 meters. So let's type the number 30 in that box. It's a good time to note that the freshwater models that use a DEM, so SDR, NDR, and seasonal water yield, they will resample all of your other spatial inputs to match the resolution of the DEM, and your output rasters will have the same resolution as your DEM. So all of your output is based on the resolution of the DEM. All right, next we'll define our output data set down here in the entry called re-projected.  Now let's click run. All right, the output raster here, DEM projected, has slightly different high and low values than the mosaic did. That's a result of the bilinear resampling that's done during reprojection, and usually that's okay. The last thing we'll do in this tutorial is fill syncs in the DEM. Syncs are errors in the DEM data, where one pixel is much higher or lower in elevation than the pixels around it. And syncs cause all sorts of problems when modeling hydrology, and we can usually fix them using the QGIS, Wang, and Lu Feel tool. To find this tool, select the processing menu, and then open up the toolbox. Up in the search window, type fill syncs, and you'll see that we have several options to choose from. The one that I recommend using is Wang and Lu. So let's double click on that to open it. The input DEM is the projected layer that we just created, so make sure DEM projected is selected. And then going down to the filled DEM input, we'll click on save to file, and once again, we'll save things in the same output folder as our other rasters. And I'm going to name my file DEM underscore fill, but normally, I would create a TIFF file for my output, but for some reason, this tool only lets us output sstat. We can easily export sstat to TIFF afterward, so we're going to name the file DEM sfill.sstat, and click save. All right, for now, we won't generate flow directions or basins, so uncheck the boxes next to those, but do keep the checkbox next to open the output after running algorithm underneath your fill down. All right, let's click run. The fill tool can take a while to run, especially if the DEM is very large or it's very high resolution. Now, you may have noticed that there are several other fill tools available. You are welcome to use any of these, but we do recommend Wang and Lu since we've found that it does a particularly good job, and it generally produces results that work well and invest. So, I'm going to hang out here while the tool runs. Feel free to pause this video and return when yours is finished. All right, once that's done, we can once again look at the high and low values for the output raster. It looks like the lowest value is now much different. It's 63 instead of 9, so the tool seems to have filled the pixels with the lowest elevation values.  Do you see the very dark spots right in here that are in the projected layer but not so visible in the filled layer? Let's zoom into one of them. I'm going to zoom into this area right here and we're going to see what's going on. Using the identify tool, let's look at the projected layer, not the filled layer yet, the projected layer, and let's click inside one of these dark areas with low elevation values. Now, in the case of the pixel I clicked, it has an elevation value of 558 meters in the original data. Just outside of that dark area, the elevation is 5200 meters. That's much, much larger. That's a big difference and it's probably not what's actually happening on the landscape. Let's turn on the filled layer now and let's see what the new value is. Inside of this dark area, it's now a value of 5128 meters and that seems much more reasonable, keeping in mind that this is the Himalaya. To verify, you could use a satellite base map to visually inspect this area, but we won't do that now. You can do that on your own for homework. The last thing we'll do is export the sstat file to a TIFF for use in and best. To do this, we'll right-click on the filled layer and select export and save as. By default, the format is geotiff and that's what we want. For the file name, we'll navigate to the place we're saving our data and I'll call the file DEM underscore fill.TIF. That's all we need to do and we can hit OK. That's enough for this session. Now that the DEM is prepared, the next steps involve creating a good stream network and delineating the watershed that is your area of interest and we will cover these in future episodes. If you have any questions or comments about this episode, we'd love to hear from you on our community forum. There's a link to the forum in this video's webpage where you can search for previous posts and create a new post under the category of training. I and other techies at NatCap will see your post and we'll respond as soon as we can. Thanks for following along.


Hello and welcome to the session. Let us discuss the following question. It says, a rod of length 12 cm moves with its ends always touching the coordinate axis. Determine the equation of the locus of a point P on the rod which is 3 cm from the end in contact with the x-axis. Let us now move on to the solution. Here we have to find the locus of the point P on the rod which is 3 cm from the end in contact with x-axis. For that we need to understand what is a locus. Locus is a moving point which satisfies certain condition. So we have a rod of length 12 cm. So let AB be the rod making an angle theta with OX. Now let XY be the point at the rod such that BP is 3 cm. So we have to find locus of this point. Now AB is 12 cm and BP is 3 cm. So AB is equal to AB minus BP that is 12 minus 3 cm that is 9 cm. Now we draw perpendicular from P or PQ and PR on the coordinate axis. Now in triangle AQ cos theta is equal to base upon hypotenuse base is QP hypotenuse is AB. Now QP has length X and AP is 9 cm. So cos theta is equal to X upon 9. Now in triangle PRB sin theta is equal to PR upon PB or BP. Now PR has length Y cm because the coordinate of the point P is PXY. So Y is the length of PR and PB has length 3 cm. Now we know that cos square theta plus sin square theta is equal to 1.  So this is the locus of the point P and we see that it is an ellipse. This is the point P phrases an ellipse. So the locus of the point P is an ellipse given by X square upon 81 plus Y square upon 9 is equal to 1. And this completes the question and the session. Bye for now. Take care. Have a good day.


Think of your accounting education as a 100 miles hiking journey with a heavy backpack. The more accounting concepts you can grasp early on in this journey, the more items you can remove from the backpack, thus making your journey reachable, easier, and faster. Three reasons why students fail the CPA exam. One, students did not learn the material in school. Two, time lag between your education and sitting for the exam. Three, the education institution you attended never showed you how to properly unload the backpack. Farhat Lectures.com can help make the journey easier, faster, and reachable by providing you with a complete solution of mini-lessons and practices of various accounting courses coupled with additional CPA resources and personal guidance and support from Professor Farhat throughout the accounting and CPA journey. Go ahead, subscribe. You will have access to all the material for one price and connect with Professor Farhat on social media.