How to Clip Data to an Area of Interest
Often, when you find GIS data, whether through an AGSL Data Request, or another data resource, it represents an area much larger than the one you wish to represent. This can present a number of problems. Working with unnecessarily large data can be burdensome and time-consuming, and many software (including ArcGIS) have size limitations for particular tasks.
This guide will show you how to use the ArcGIS Editor tool bar to quickly create a new layer with an extent of your choice, and then use this layer to clip any vector data you are interested in working with.
Let's get started.
Below, please find the "before stage". This is an unclipped elevation data layer that we will use to demonstrate how to clip any vector data layer to a specific area:
Step). Add a basemap
After loading your data in to ArcMap, adding a basemap will allow you to more easily identify what area of the map you are looking at.
1). Next to the Add Data button, there is a small dropdown arrow. Click this arrow.
2). Click "Add Basemap".
3). You will be able to choose from various basemap style options. Typically, "Streets" is a good one to choose for quick reference.
4). Click "Add" to add your basemap.
Now you can see which area is covered by your contour lines.
Step). Create Clipping Layer
In order to clip your gis data, you will have to create a clipping layer the size of the area you are interested in, to clip the data layer with.
To do this, you will need the editor toolbar.
1). Access this toolbar by clicking Customize > Toolbars > Editor
You will also need to know the projection of the GIS data you wish to clip.
2). To find this, right-click the shapefile in the table of contents, and select properties.
3). Under the "Source" tab, take note of the coordinate system.
Now that you know the projection of your GIS data, you can create your clipping layer.
4). In your catalog tree (on the right), right-click the folder that your data layer is in, and select New > Shapefile
5). Name your file "clipping," make the feature-type "polygon," and give it the same coordinate system as your GIS data.
6). Add new shapefile to map by dragging it from the tree into the map. You will see it appear in your table of contents, but will not see a visual change in the map, because it does not have any geography yet.
7). On the editor toolbar, choose "Start Editing"
8). In that same drop-down, now select Editing Windows > Create Features
9). Select your clipping layer and choose rectangle under Construction Tools.
10). Create a rectangle around the GIS data you would like to keep. Double click when you are done to finalize your shape.
11). Click Editor > Stop Editing, and save your edits, using the editor drop-down button.
Now we are ready to clip.
Step). Clip the data
1). Select Geoprocessing > Clip
2). Populate the clip tool with the following preferences:
Use your gis data as the input feature.
Use your new rectangle as your clip feature.
Save to a place you can easily access it.
3). Click "OK" to run the tool.
Now you have GIS data for just the area you are focused on.
