Extracting the geographic features you need from a larger dataset

You may have noticed that many GIS datasets contain information about a geographic extent that is larger than your area of interest. Your research may involve analysis of data related to a single municipality in Ontario, yet you have only been able to locate a dataset showing all municipalities located within the province. Alternatively, you may be interested in only displaying a selection of features on your completed map, such as the Canadian cities you have selected as case studies for your research. This tutorial will demonstrate how to extract just the features you need from larger datasets, saving them to new files that you can then use to map and analyze your data.

  1. Use the Add Data button to add the dataset you are interested in selecting from to your map document. For this example, we will use a shapefile that represents the municipalities that comprise the Toronto Census Metropolitan Area (a component of DMTI’s CanMap Route Logistics suite of products) to create a new dataset that depicts just the boundaries of the City of Toronto.
    Screenshot highlighting the Add Data button.
  2. Right-click on the name of the dataset in the Table of Contents, and select Open Attribute Table.
    Screenshot showing where to Open Attribute Table.
  3. Click in the grey box to the left of the row in which the City of Toronto appears. The row will be highlighted in blue. (If you were looking to select multiple municipalities, holding down the Ctrl key will allow you to select more than one at once.) Close the attribute table and return to the map. The outline of the city of Toronto will be highlighted in blue.
    Screenshot showing the city of Toronto outlined in blue.
  4. Right-click on the name of the layer in the Table of Contents, select Data, then Export Data…
    Screenshot showing where to select the option to Export Data.
  5. In the Export Data window that appears, the Export: dropdown menu should read Selected features. Depending on the coordinate system you are working in, you may wish to select an option other than “this layer’s source data” when assigning a coordinate system to your output dataset. Click the folder icon next to the Output feature class: box to assign a file name and destination to your output dataset, using the Save as type: dropdown menu to indicate whether you would like to save the output as a shapefile or as a feature class within a file or personal geodatabase, clicking Save when you are ready to export the file, then OK to complete the export process.
    Screenshot showing the Export Data window in ArcMap.
    You will be asked whether or not you would like to add the exported dataset to the map. Your reduced dataset is now ready for display and analysis.
  6. Alternatively, you can use the Select Features tool instead of selecting rows from the attribute table to interactively select features from the map by clicking on them (holding down the Ctrl key in order to select multiple features.
    Screenshot highlighting the Select Features tool in ArcMap.
Data format: 
Utilities: