How do I create a fixed distance buffer in QGIS so only one side of the buffer (inside) is processed? I have a big shapefile to buffer and can't be expected to edit the nodes that lie outside each polygon. If I type a negative value in the buffer window, the entire inside of the polygon fills, even with a distance of 1.
The goal is to create a border to a polygon which is styled to the inside of that polygon. If there is another way about doing this do let me know.
Projection is British National Grid (EPSG: 27700)
Best Answer
What you are experiencing is the expected behaviour of a negative buffer. The negative value is the distance from the boundary, so a value of 1 will be one unit of the layer's CRS from the edge. So, if your CRS units are meters, the buffer polygons would be almost identical to the originals, just 1m smaller. If your units are degrees, you will get some 'interesting' results.
So, you could use your described approach and set the negative value but style it to hide the interior of the original polygon. Or you could create a proper doughnut by following the described procedure and then differencing the original polygons and the interior buffer.