How to Convert a Polyline to a Polygon in ArcMap
ArcMap prepares, manipulates and interprets geographic data through maps and geographic information systems, creating a map with layers of information about different points. It is the main component of ArcGIS from the developer Esri. ArcMap allows you to create a map and fill each point on the map with information relevant to that location, such as precipitation rates, literacy rates or elevations. To add this information, establish the areas on a map with which to associate the information, a process that requires creating closed polygons out of the lines that make up the edges of an area.
Things You'll Need
- ArcGIS software including ArcMap
- SHP (shapefile) with polyline data for the map
- SHP (shapefile) with polygon data for the map
- SHP (shapefile) with point data for the map
Creating a Geodatabase
Open ArcMap and create a new map under the File menu.
Select the SHP files containing your polyline data from the dialog box that appears as soon as you open a new map. ArcMap creates the new map with the polylines – a set of lines grouped together – from the selected file.
Click on Data Management Tools in the main menu and then select Workspace and later Create Personal GDP under the sub-menus. This step will create a new geodatabase into which you can input the polylines.
Select the output location folder for your geodatabase, give it a name, such as "example.mdb," and click on "OK."
Click on Data Management Tools and then Workspace and Create Feature Dataset in the sub-menus. Set the output location to the database you just created, example.mdb, and name the dataset with a easy-to-remember name like "test." Click on the "Properties" button in the dialog box, and then import the SHP file containing the desired polygon data. Click on "OK."
Select Conversion Tools in the main menu and then To Geodatabase and Feature Class to Geodatabase under the sub-menu options.
Drag your SHP file with point data and the polyline SHP into the input box. Set the output geodatabase to the dataset you just created, example.mdp/test and click on "OK." This creates a dataset that associates your polylines with a specific point on the map. Refresh the map using your dataset to verify the results.
Turning Polylines into a Polygon
Select Data Management Tools from the main menu, followed by Features and Feature to Polygon in the sub-menus.
Select your polyline file from the dataset directory, example.mdb/test, as the Input Feature.
Select your point file as the Label Feature and select a name for the output, such as "example_polygon." Click "OK" and refresh your map from the new file to see your polygon in place.
Tips & Warnings
- ArcGIS files are made up of lines, polygons and points. All polygons also have point and line data, which is why you have to merge your data into a geodatabase before creating a polygon.
- Check your polygon for accuracy and coherence with your data. Edit the geodatabase if you find any errors.
- For experienced coders, ArcGIS also offers code solutions to feature transformations. In standard cases, you may also be able to look up a code for what you want to accomplish and simply past it into the directory.
- Save your work often. ArcMap is a robust and heavy program that can freeze on slow operating systems.