Converting Road shapefile with line geometries to another shapefile with polygon geometries by adding buffer to line on both sides using QGIS

Question

I have Roads shapefile which are denoted by lines.

I want to create another shapefile of roads as polygons, by adding 10-meter buffer on line.

How do I do this using QGIS?

Answer 1

QGIS should be able to do that easily without any plugins.

First, you will need to make sure you are using the correct projections. You may already be doing this, and setting projections can be cumbersome depending on where your shapefile is located in the world, what projection it is in etc.

In QGIS, go to the "Vector" menu, choose "Geoprocessing Tools", and "Fixed distance buffer".

• set your Input Layer to be your "Roads" line layer
• set the Distance to 10. This is where your projection is important, as it is important you've projected into a coordinate system that uses metres. Also, bear in mind that this is 10 metres on either side of the line (so your road is 20 metres thick). If you want it to be 10 metres thick, set your Distance to 5 metres
• Segments controls how complex, or curved, your resulting shape is. During the process curves may develop. The higher the Segments, the less jagged the curve is. I usually select 25
• Dissolve result. Do you want to keep the individual roads, or do you want them merged? If you want them merged, use Dissolve Result

You can then also choose whether you want the result to be a temporary layer (you will lose it when you close QGIS), or if you want to save it elsewhere. Note that you can still save the resulting layer afterwards by right-clicking it in the layers panel and using "Save As".

The above is for QGIS 2.18, but the same basics should apply for all versions of QGIS.

If you want them to be of varying thickness, you could always specify the thickness in a field in your Roads line shapefile, then use the "Variable distance buffer".