I'd like just give you a little brief overview into working with projections in ArcMap. Here I have two different features classes. They're two different versions of the same data. One is in GCS, and one is in, in Conic. And what does that mean, GCS means geographic coordinate system. That means that it's not projected, that it's being stored in a three dimensional spherical coordinate system with latitude and longitude coordinates which are angles. So that's one way of storing the data. The second is in a Conic format that's actually an equal area conic format. So I've got the same data stored two different ways. And what that actually means is that the coordinates that are being used to map the same locations will be different because I'm using these two different coordinate systems. So what I'm going to do is add in the geographic coordinate system version of the data. And you'll see that, one, ArcMap has given it this kind of blah color which I'm not really thrilled about, but we can always change that later. But this is an unprojected version of the data. Now, yes, in order for it to be shown on a two dimensional screen, there's some kind of, sort of let's call it a pseudo projection screen that's being used by the software. But as far as we're concerned in terms of any calculations that are being done or the map that we're creating, we can think of this as being unprojected. And if you're familiar with Canada, one of the things that's always a tip off for me is that if you look at Ellesmere Island it's completely distorted. It always kind of looks like it's shooting off to the right there. The rest of the country looks a little bit squashed as well. And so whenever I see a map like this, if it's a map of Canada and maybe you are more familiar with wherever that you are live in. Is that when I see this it kind of tips me off that the person that created the map didn't project it properly. And that's always a bad sign because that makes me think, is that that they didn't know any better or that they just have poor attention to detail. So once you get familiar with these things, you start to notice them more, and it's something that you really want to avoid. You want to have a correct projection that's suitable and appropriate for the work that you're doing, and to know to make those choices. Okay, anyway, so what we can do is right click on the data frame, select properties, and select the coordinate system that's more appropriate. So you'll see that that's actually set to WGS 1984, which is under the geographic coordinates systems, which are 3D. And what I like to do is select something that's a projected coordinate system. And I'll go under Continental, North America and pick the Canada Albers Equal Area Conic, that seems like a good one. Okay, now, what this is warning you about and you'll see this warning often is it's saying wait a minute, you're trying to display the data in a different projection and coordinate system than it was stored in. And so that could lead to problems if you don't know that's what's happening because this is something that's super important. Is that any of the calculations that are being done on this data set. If you were calculating the areas for example of different provinces or something, those are going to be based on the data that's stored in the file which is not projected. Not on the data, or not on the projectionist in terms of the way that it looks on the map. So what this is warning you about is saying, wait a minute, you're welcome to do this, you can reproject it if you want. But I need the calculations that are being done or being done in the format or the projection is being used that it's stored in. So I'm just going to say OK, you can say don't warn me again in this session or don't warn me ever. For now I'm just going to say, do I want to do this anyway? And so now you see that Canada looks very different. I'll just, zoom in a little bit here. For example, you can see that Ellesmere Island now looks a lot better and we have this sort of more familiar shape to Canada that you may have seen on maps in other places. So maybe what I'll do now just to point this out is that I can export this data, if I say right click on the feature class and say data export data. I have the option of exploring that data in the same coordinate system as the data frame, here. So if I do that, since I've set the data frame to a projected coordinate system, I could output that into a second feature class. And let's just do that just for kicks. Even though I already have one, I'll say Canada, what did I say? It was all just a Equal Area Conic, which is EAC, which is my little short form, and say OK. And I'm not going to add it here. But what I am going to do is I'm going to create a new empty map document. We'll just go with the default kind of template, we're not going to save our changes. Go to the data view. Now, if I add in that one that I just created, if I drag that in, notice that it's automatically projected, because now, that projection is stored inside that feature class, so that's part of the data. In fact, the coordinates that are being used to store that data are different. They've been converted or transformed or calculated for that particular projection that I have. So it's a really important concept is that when you create an ArcMap document the first data set that you add to your data frame will set the data frame to that coordinate system, and if it's projected to that. So that's a convenient thing if you know that it's doing it, but it's very confusing if don't know that it's doing it. So that's just something I wanted to point out. Now, for example, if I wanted to make a map of let's say, Yukon. Notice that it's over there kind of on the west side of Canada. And with the conic projection you kind of have this sort of arc to the way that the country looks. And that the Yukon is sort of off on one side and that's normal if you're making a map of the entire country. With this kind of a projection that's the way most people would expect to see something like that. Where things get a little tricky though is what if you're making a map of just Yukon? Then you want to customize your projection in order to be able to make it look its best for people that want to just look at that one area. And this is a common mistake that people make. So let's just see how this could work. So the first thing I'm going to do actually is I'm going to take that selection and I'm going to save it as new feature class. So if I just go Data>Export data. And I'm going to say export just the selection features which is just Yukon. And I'm going to use the same projection as the source data because this is actually already equal area conic. And I'm just going to, Call that Yukon. And we're going to save that and add it to our map. Now, let's say I have a brand new map. And I just add my Yukon data. So if I was making a map of Yukon, and especially if I lived in that are I think I would find this particularly annoying. Is that it's meant to look based on this projection that it's being set to as though the whole thing is kind of falling over like it's about to tip over, and fall on its side or something. That's not the way the Yukon actually looks. You might be used to seeing it that way because it's on one side of Canada. And this is true whether it's Alaska, or anywhere where it tends to sort of be on one side of a larger region or country or whatever, is that it's really not a customized way of showing that particular region at it's best. So what we're going to do is customize the projection to something that's particularly useful for that area. It's very easy to customize a projection, we can just right-click on the data frame, select Properties and we have our coordinate system tab selected all ready. And so you'll see that right now, this feature class is being stored as Canada Albers Equal Area Conic. What we can do is just right click on it and say Copy and Modify. And so now I can change the central meridian, I can change the standard parallels. The central meridian is certainly a big one in terms of making sure that it looks like Yukon and the projection is centered on Yukon. So I'm going to set it to 132.5, which happens to be the central meridian that's used by a lot of maps for the Yukon I happen to know that. So before we even change the standard parallels let's just do that, and say OK, and so suddenly voila, we have Yukon centered correctly. It doesn't look like it's falling over anymore, and anything else that I want to do with that map it's just going to look a whole lot better. That's fine in terms of appearance, but in terms of distortion and measurements, we can also make another change to the standard parallels to minimize distortion and improve the accuracy of the measurements that are being made. If I go back to my properties and I customize this again I can change the standard parallels to let's say 61 and 68. Say OK, and it didn't seem to change it that much. But you know what? There was a slight change in the way that it looked. And so all that's happening there is that I've set them so that the standard parallels instead of being all for Canada, so way down there and way up here. As I set them so that they're spaced inside the mapped area that I'm interested in, in this case Yukon. And the idea is that remember that there's no distortion where the standard line touches the developable surface, which in this case would be this standard line and this standard line. So there's two standard lines, so it's a secant case. So we have the reference globe cutting into the developable surface at two locations here. And so we've specified them to be up here and down here. So that there's not very much distortion in between. So the scale factor will increase, actually between these two lines will decrease. And then beyond it will increase but it will be at an amount that's acceptable for a map that's being made for this size of a region of this scale. So that's a way of being able to customize that. So it was really easy to do. All you have to do is customize the central meridian, customize the standard parallels. You can do that at once, I just did it in two steps to kind of show you how that worked. And then you've got a customized version of your projection. And now, you could export this data set using the same coordinate system as the data frame. And so we'll call this yukon_customized, actually let's say eac, because that helps me remember that it's equal area conic, and I'm just going to say custom. I could have used my initials, sometimes I'll put DB in or something like that. There's various ways that you can do this. And so now, we have a new feature class that's stored without customized projections. So that, if I give that data to someone else or if I add it into another map document, we'll already have that projected version of the data stored inside that feature class and it's kind of packaged up if you will. And so whoever uses in whatever mapped document you'll already be in that customized projection to be used. So it's a really handy little thing to know. It's useful in terms of customizing them, making your maps look better and minimizing distortion as much as you can.
