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A lot of data is available on the internet in simple tables that provide latitude and longitude values. In the GIS world, this are known as XY data files. They can be files like a Microsoft Excel Spread Sheet or Comma-separated Value CSV file or many other tabular data formats. The key factor is that they have location attributes right in the table and if they do they could be mapped in ArcMap. Let's go ahead and take a look at one. From the catalog pane over here, I'm going to go into the Seattle folder. And I've got a file called Heritagetrees.csv. If I double click on it, it'll open up on the default program on my computer, which in this case is Microsoft Excel.
And I can see that it's just a simple data table. Let me expand these cells open a little bit. That includes the Feature class of Heritage Trees. It has a name of a tree, the address of where this tree is located, a link to a website about that tree, and then we also have longitude and latitude values that are the coordinates of where that tree is located. Now, we can go ahead and map these tree in our ArcMap. Let me go ahead and close Excel here, and I'm not going to save any changes. And back from the catalogue pane, I'm going to take the heritage trees CSV file and drag and drop it on top of my map layout.
Now my table of contents switches over to this list by source mode because it can't yet quite display this data. It doesn't have enough information. In order to display the CSV file what I can do is right click on it. Go down to Display XY Data and we'll fill out this window. The X field is the horizontal axis, which is equivalent to longitude on the globe. The Y field is going to be our latitude axis. We'll go ahead and accept the rest of the default options and say OK. Now our table doesn't specify any object I.D. fields. So we're not going to be able to make selections. Which is totally fine in this case.
Go ahead and just say okay to this window. And our points should now be plotted on the map. But we don't see them. So what's going on? Let me go ahead and press this world icon here. To zoom out to the full extent. And you can see that we have some new points added way off here at the coast of Washington. This is actually a really common problem, and to figure out why this happened we need to think about coordinate systems. One thing that we can do is look down to the status bar down here, and see that my current coordinate system is measuring in feet, and I can try to find the origin of my current coordinate system by moving my mouse around to minimize these values.
And you notice as I get over here towards where these points are appearing it appears that this is where the zero, zero location for the current coordinate system is located. You'll see that both these values switch back and forth between positive and negative integers as I move right around these points. This clues me in that there were probably in a state plain coordinate system. We can confirm this by exploring the properties of the map by going up to those layers here, double clicking and taking a look at the coordinate system. And indeed, we see we're in a state plane, Washington South mode. The state plane systems are different for every state of the United States.
And they count up the distance in feet, north and east, from a common starting position. In our case, the common starting position is way over here off the coast of Washington. This is our zero, zero location. The other piece of the puzzle comes in the data that we're trying to map. In the Heritage Trees file, if I open it one more time, I'll go to the Catalog, double-click on Heritage Trees. The numbers that we're mapping are negative 122 by 47. Now, we know this as the longitude and latitude pair of this point. But ArcMap doesn't know that. There's no units listed here.
And so when we try and import this data, ArcMap is interpreting this as down 122 feet from the origin, and right 47 feet from the origin, which isn't the lat, same as latitude and longitude. So let's go ahead and go back into ArcMap and we'll fix this problem. I'll go ahead and close Excel. I'm going to go over here and right-click on my Heritage Tree Events, and I'm going to remove it from the map. That'll leave the data table still in the map. Let's go ahead and plot those XY points one more time. I'll right-click on it, I'll say display XY data. We'll return back here, our X field is still the longitude column, our Y field is still the latitude column.
But down here, we need to specify what coordinate system these points are in. Instead of the state plane system, I'm going to press Edit. These points were most likely gathered by a GPS receiver. So we're going to choose our coordinate system from the geographic coordinate system folder. I'll scroll up to the top. Close out Projected, and open Geographic coordinates. And then I'm going to go down to World. Here and expand that open and I'm going to scroll down until I get to the WGS1984 which is the common system used by GPS loggers. We'll go ahead and say okay and then one more time we'll say okay.
Once again we'll say okay to this warning message and you notice that our points now display right around the city of Seattle. I can use my bookmarks, zoom into the city of Seattle, and I can see the various trees. Now I can use my identify tool on a tree to see the other attributes including its website or a pdf file of where this tree is located, including an image. So just because your data might not be in a geospacial data format like a geo database or a shape file, doesn't mean that you can't map it. As long as you have simple location attributes, you can add nearly any kind of point data to your ArcGis projects.
It might take a bit of sleuthing to find out what coordinate system they're using, but once you know that information, it's just a matter of telling Arcmap what those numerical values are, so that it can interpret them correctly.
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