I have a vector line made of different pieces of lines with different directions. I merged the lines to one. But this merged line still have different direction in its "invisible" parts. I want to plot a profile, so I need ONE direction. Any idea?
Both qgis and GRASS have tools to switch line direction. In QGIS you need the (experimental) plugin Swap Line direction. In GRASS you can use the v.edit module with "tool-flip"
However, in both cases, you'll have to manually select which line segments to flip, and which to leave as they are. I don't think there's any way around that.
Not sure if it will work for you, but can you create a topology with a sink at the end of the line in the direction you want the line to run?
