Clipping data to a study area
Video: Clipping data to a study areaOften you'll have access to a large master data set for your geographic region when the particular area that you're interested in is just a small portion of that region. When you have a small study area, or are focusing on just a specific portion of a region, it's not really practical to bring in all of that extra data that lies outside of your area of interest. That's where the Clipping tool comes in. By making a copy of only the data that falls within the study area and get rid of all the stuff that's outside, you can dramatically increase the efficiency of your map documents and make them render much more quickly.
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Get up and running with ArcGIS, a true geographic information system (GIS) that allows you to dig into highly accurate geospatial data in a way other mapping applications can't compete with. It's great creating maps, analyzing data for land use studies and other reports, and preparing data for use in an application or database. Let Adam Wilbert show you how to display, analyze, and illustrate geospatial data with ArcGIS. He explores how to import data from multiple sources, manage it with the ArcGIS catalog, and then start making maps. Learn how to lay out your data in the ArcMap component; add symbols, scale bars, and legends; and get your maps out of ArcGIS and into the real world, whether it's for printing or export to another application.
- Understanding vector vs. raster data
- Modifying metadata
- Adding data to a map
- Importing data from online providers
- Labeling features
- Joining data
- Clipping data to a study area
- Working with map layouts
- Creating a legend
- Printing and exporting the map to a file
Clipping data to a study area
Often you'll have access to a large master data set for your geographic region when the particular area that you're interested in is just a small portion of that region. When you have a small study area, or are focusing on just a specific portion of a region, it's not really practical to bring in all of that extra data that lies outside of your area of interest. That's where the Clipping tool comes in. By making a copy of only the data that falls within the study area and get rid of all the stuff that's outside, you can dramatically increase the efficiency of your map documents and make them render much more quickly.
So let's suppose that we're performing some analysis on the Queen Anne neighborhood in Seattle. I'm going to go up and use a bookmark created for Queen Anne neighborhoods to zoom into the right area. I'm also going to go ahead and turn off the building polygons and the highway lines so we can see which neighborhoods we're talking about. Now, the first thing we need to do is to extract just the boundary of our study area, and we can do that by selecting the four polygons using the Select Features tool here. I'll click on the first polygon and then I'll Shift click on the other three. Now I'll go over to the neighborhood's layer in the table of contents. I'll right click, go down to data, and choose Export data.
Here I'm going to export only the selected features. I'm going to use the same coordinate system as the data course so that won't change. And down here I'm going to choose where I'm going to save the file to. I'll go ahead and press the Browse button. And inside of our working directory, I'm going to create a new Geo database. I'll name it Queen Anne and I'll press Enter and then double click to go inside the geo database. Now I can give my feature a name. I'm going to call it Queen Anne neighborhoods. Go ahead and press Save and OK to Create a File. After the File's created, art map will ask us if we want to add it in the map.
Go ahead and say Yes. And now we can turn off the rest of the Seattle neighborhoods. So now we're only left with the Queen Anne neighborhoods by themselves. Now the building polygons and highway lines are extremely large data sets. Lemme turn those both back on. And these two layers include the entire Seattle Metro area. This particular data set is an extract from the global open street map.org database. And it was built by a community of volunteer mappers from all over the world. For our purposes, we can ignore everything outside of the Queen Anne neighborhoods.
So we're going to clip or extract just the pieces that we want to keep. This'll also help us create a nice and clean final map layout later on. Now the tool that we need is part of the Arc toolbox, so I can go ahead and activate that if it's not on your screen. And inside of the toolbox, we're going to go to analysis tools, extract, and we're going to find the Clip tool here. I'll Double click on it to run and the Clip tool requires some input features, some clip features, and some output feature classes. If we're not sure of what any of these features are, we can press show help down here on the bottom, and it will help walk us through the steps.
So if I click on Input features here it tells me that the Input features are the features that are about to be clipped. We want to clip our highway lines. So I'm going to drag highway lines and drop them on input features. Next, I'll click on Clip features down here and it says the features that are used to clip the Input features. This is going to be our Queen Anne Neighborhoods shape. Let's drag Queen Anne Neighborhoods and drop it here. Finally, it wants to know where we want to save this. We click on the Browse button. We'll go into our Queen Anne geodatabase, and here we're going to call it Queen Anne roads. Go ahead and press save, and we'll say okay to run the tool.
It's going to take just a moment, and you can keep track of the progress down on the bottom of the screen. And when it gets done, we get a new layer called Queen Anne roads up here at the top. Now let's do the same thing with our building polygons. I'll run the Clip tool again. This time theInput features are going to be our buildings, here. The Clip features are going to be the Queen Anne neighborhoods, once again There, and the output feature class we'll save in the Geo database, and we'll call it Queen Anne buildings. Go ahead and say Save and OK to run the tool one more time. After it gets processed, we can go ahead and turn off the overall building polygons and highway lines, and we can zoom back in using our bookmarks to the Queen Anne neighborhoods.
And now we can see just the roads and buildings that lie within that neighborhood. So now we have a nice and clean study area, ready for our analysis or cartographic presentation. By using the Clip Geoprocessing tool, we were able to cleanly cut the massive roads and building layers precisely at the boundary of our study area.
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