One thing that can be a little confusing with ArcMap when you're first using it is the red exclamation mark that can come up in a map document. What am I talking about? Well, let me show you. Remember with a map document that it's storing what data to include in the map document, and how to show that data. And where that data are stored or is stored, depending on how you want to say it. And so if that data gets moved, then the map document no longer knows where it is and it can't add it to the map. So I think I can show this to you by trying to replicate the problem. Here's my map document that I've created for Toronto fire stations. And so it's actually stored in the map document that if I want to show my fire stations in here. That that's way over here in this geodatabase inside the Toronto geodatabase. That's where it's stored. And so when I open that map document, it goes and says I need to look in this drive, in this folder, in this geodatabase for future class with this name. And then I have to add it to the map and show it a certain way. That's what the map document is storing and that's what it's doing when you try to open that map document. So let's see what happens if something changes with that scenario. Either the feature class gets renamed, or moved, or deleted. Then the map document won't know how to find it anymore. So let's see if I can do this. Perhaps I want to move. I'm going to create a new file geodatabase. And I'm going to move one of these feature classes into this, so if I just wanted one for fire stations, let's say. So it's going to be its own file geodatabase, I can do whatever I want. I've called it fire station, good enough. And let's say that I copy that data and paste it into this new geodatabase. Yep, that's what I want to do. So it does that. So now I have a copy of that data. And then I decide that I don't really need it in my original one anymore, so I'm going to delete it. It says, are you sure? I say, yes, and so now that data has been deleted from my geodatabase. So now I'm going to create a new, I'm going to open a new map document just so that I am getting out of the map document that I'm currently in. And if I then open my original map document, you'll see that what's happened here is that I now have, it's just opening it here. Just give it a second. So it's drawn the roads and the vegetation. But we have this red exclamation mark right there next to the fire station's entry. And so what that's doing is it's saying, I know I'm supposed to be showing the fire stations. I know that's part of my list of data but I don't know where it is anymore, so I can't show it to you. So that's what the red exclamation mark is for, is it's to show you that I can't find, or software can't find the data, okay? So how do we fix that? It's really simple, all you have to do is to tell it where the data went to. If we right-click on this we can say, data, repair data source. So we're basically going to tell it, where did it go. So I'm going to navigate to my new file geodatabase here. Tell it that's where it went, say Add. So the exclamation mark disappears because it now knows where it is. It's drawing it because it's found the data and it's able to draw it with the symbology that I stored in that map document. The only last thing I want to mention here is that you have to save the map document again in order for it to save that new data location. If I didn't do that, I would have to go through exactly the same process again every time I opened it. All I have to do though is save this map document. And then it will save that new location for the fire station data and everything will work well. If you want to try and avoid the dreaded red exclamation mark, there's a trick that you can use to that will mostly help you with that. And what that is, is that if you go into the File, Map Document Properties, there's a couple of things in here that are helpful. One is to make sure that we've checked this box that says store relative path names to data sources. So that is right there, make sure that's checked. And what that will do is it will store the fact that all of these feature classes are stored in the same file geodatabase, for example, and within the same folder. The fact that it's relative means that it doesn't matter what drive it's on. It could be on your C drive, your D drive, or some USB drive, whatever it is. It could X drive, it doesn't matter. The fact is that if it's in the same relative location, if you open that map document. And all of the feature classes and data that are needed are in that same relative location, like let's say inside the same folder. Then it will be able to find everything, and you won't have the red exclamation marks and you won't have to repair the data. It's not totally foolproof, especially if you're using data from multiple sources that may be moving around but it's a good way of avoiding as much of that as possible. One way that you can do this, make sure that this happens, is if you go under ArcMap Options. And go to General, you can see that you can check this box, make relative paths the default for new map documents. And if you check that, which I don't believe it is checked by default, I've just already done it here. Is that anytime you create a new map document, that relative path option will be selected automatically, which just saves you a step. It's just one of those things that is really helpful to be able to know that it's there. One other thing that's useful to know is that you can set the home geodatabase for your map document. So if I go back to the Map Document Properties, you'll see there's an option here for the default geodatabase. And one thing that's really confusing, at least that I've never really liked, is that if you don't set this. It will set it to a default geodatabase that's usually buried somewhere in a document folder that you probably don't even know where it is. It could be under, in Windows it could be like users. In my case boys, slash, asterisk, slash ArcMap, whatever. And it's not something that's going to be obvious to you when you go looking for that file or that feature class. You thought you saved it now you don't know where it is. So my recommendation is to always create your own file geodatabase for a project, set it as the default geodatabase. And so then any files, or anything that you create after that will automatically go into your default geodatabase that you created, and you know where everything went. Once you get a lot of map documents, and a lot of feature classes and geodatabases and things like that, it can be easy to lose track of all of them. So I'm just using this as a way of telling you it's a helping hand to make sure that you keep things as organized as possible. All this really means is that you go into here. Click this little browser thing, and then in my case I would want to make the Toronto geodatabase my default, I click Add, say OK. And you'll notice that in the, Arc catalog pane, a couple of minor things that happened, but they're very useful. One is that, you'll see that the Toronto.gdb is now in bold and there's a little house symbol that's been added to the geodatabase symbol. And that's to indicate you that's the default geodatabase. So for example, if I wanted to export data and make a copy of it. And I wanted to choose the location. If I select the default geodatabase, it will automatically go to that default geodatabase, and I can just add it in there, that's all it's doing. And if I click the Home folder, that's the folder that the geodatabase is in, and it's also where the map documents is located. And I won't save it here just because I don't need to. So I hope that makes sense to you, I just wanted to point that out so that you're clear when you see that red exclamation mark. That it's nothing to really worry about you just need to set the location of that data and that will fix it for you and then save your map document and that will take care of it. There are some other things in there that I hope make sense in terms of the default and so on. That it's not really clear when you first start it but I hope that will save up a few steps and a bit of aggravation.
