Sometimes if you’re working with a large geographic dataset in QGIS, you want to select a smaller geographic section and convert it to a new file. Here is a step-by-step tutorial on how to convert a geographic selection from one GIS dataset into a new GIS file using QGIS.
Select the Geographic Area of Interest
In the layers menu section on the left-hand side of your QGIS window, highlight the layer that you want to perform a section on to make it active (1). Next, select the “Select Features by area or click” icon located on the upper icon menu strip (2) and then select the method by which you want to select your geographic features.
Now use your cursor to highlight the geographic area you want to select.
The highlighted geography will turn a bright yellow color.
Export the Geography Selection to a New GIS Data Set
When you have selected the geographic features that you want to export to a new GIS data file, right-click on the layer in the legend window and select “save as..”
The window that pops up provides several options to choose. First, under format select the file format (shapefile, GeoJSON, KML, etc.) you want to export the geographic data as. Next, in the save as section click on the browse button to select the file directory to save the data to in the window that pops up. This is also where you will type in the file name that you want the GIS data to be saved as. Finally, in the encoding section, make sure the “save only selected features” option is checked. You can optionally set other parameters in this section if desired. If you want to load the new layer into your legends window, make sure the box for “add saved file to map” is checked (typically this is already on by default).
Click on OK and your new file will be save to the designated directory and added to your open QGIS file.