Fixing bad topology on polylines with QGIS

Question

I've been sent a shapefile containing 12 layers of some city's road system. Each layer depicts a portion of the road system, and all of them partially overlap on the map.

I'd like to work on the sum of these 12 layers in order to have the broadest extent of the road system. The problem is that the person who digitized the analog maps to create the shapefile didn't use the snap feature, and the line segments and their vertices don't exactly overlap where they should.

How would one sensibly deal with this kind of data? Is there a way to automatically correct these messed up topologies?

Answer 1

Perhaps the Snap option of v.clean could solve your problem.

I tested this with two different reprojections of a single line to create more or less parallel running lines. v.clean turns them into a single line, but also eliminates a number of vertices. If you can fine-tune the threshold setting to minimize this loss of detail to something that is acceptable to you, it could work.