{"id":178,"date":"2013-04-29T23:19:09","date_gmt":"2013-04-29T23:19:09","guid":{"rendered":"http:\/\/www.lincoln.ac.nz\/conversation\/gis\/?p=178"},"modified":"2023-05-07T00:22:42","modified_gmt":"2023-05-07T00:22:42","slug":"how-do-i-clip-data","status":"publish","type":"post","link":"https:\/\/blogs.lincoln.ac.nz\/gis\/how-do-i-clip-data\/","title":{"rendered":"How do I Clip Data?"},"content":{"rendered":"

This post covers a very useful skill – clipping subsets of vector <\/strong>data from larger datasets (clipping raster data<\/a> is covered in another post – Updated May 2021 for Pro). <\/em><\/p>\n

As seen is some earlier posts, most of the\u00a0data on the J: drive<\/a> is at a national scale. \u00a0In many cases, though, you’ll be working at a much larger scale (and by that I mean a smaller area in the Cartography sense of scale). \u00a0The Clip tool<\/a> is what we’ll use to do this. \u00a0Like a cookie cutter, the Clip tool uses the boundary of the polygon to clip out the data inside the polygon; this can be done on points, lines or polygons, but we must have a polygon layer that defines the area we’re clipping.<\/p>\n

Sometimes you’ve already got a polygon layer that you can use – that’s what we’ll talk about here. \u00a0Other times, you need to create a new polygon layer – this post covers<\/a> how to create a new feature class or shapefile.<\/p>\n

Now onto clipping. \u00a0If, for example, we wanted to clip out all of the roads within the Canterbury region, I would add the road_cl.shp (road centrelines – a massive layer at the best of times) layer from J:\\Data\\Toposhapefiles:<\/p>\n

\"\"<\/a><\/p>\n

Next, I need a polygon layer that shows the extent of the Canterbury region. \u00a0I’ll add the regions.shp layer from J:\\Data\\Administrative_Boundaries. \u00a0Note that this gives me all the regions but I want to use only the Canterbury Region, so I’ll go into the Attribute table and select the Canterbury record – note how it’s outlined in blue. \u00a0With most tools in ArcGIS, if a tool is run on a layer that has any features selected, it will only work on those features. \u00a0(Alternatively, with the Canterbury region selected, I could right-click on the layer name and go to Data > Export Data<\/span> to create a new layer with just the Canterbury region in it and use that as my boundary.)<\/p>\n

\"\"<\/a><\/p>\n

Now I’ll run the Clip tool. \u00a0You can find it in two places, either:<\/p>\n