# Why does clipping a line layer using a polygon result in an empty shapefile?

I am using QGIS 2.2.0 and want to clip a line layer (roads) so that only those inside a polygon are shown. When I do this using Vector->Geoprocessing Tools->Clip I only get an empty shapefile as an output. I have tried transforming the original road shape file from multipart to singlepart before clipping and still have the same problem.

I've included a screenshot of what I am trying to do.

Does anyone have an idea of what is going wrong or something to do differently?

• Are you sure that road layer and polygon layer have the same CRS? If you turn On-the-fly-reprojection OFF, do they still align? – AndreJ Apr 17 '14 at 14:30
• @AndreJoost you're right they don't align, but when I try to use the same CRS as the polygon layer (a user generated one) I have the problem that the two layers don't match anyway. Instead I used WGS 84 for the road layer to get them to display on the polygon. Maybe I should address this problem first... – Katie Apr 19 '14 at 8:04
• Surely. If they don't align without on-the-fly-reprojection, clipping won't work. – AndreJ Apr 19 '14 at 9:44
• @AndreJoost, I'm new to QGIS so please forgive me if my questions are obvious, but is there a way to to get the two layers to align? – Katie Apr 22 '14 at 13:18
• What CRS do your layers have? What extent is reported under properties, metadata tab? What is your project CRS? – AndreJ Apr 22 '14 at 15:05

1. Save the polygon layer with Rightclick -> Save As ... choose a new filename and WGS84 as CRS