qgis - How to get the center line between two linestrings

Where is the track of a ship when it is shipping always in the center of the English Channel between the coasts of Great Britain and France?

1. I started with 2 linestrings and I created a lot of points on the linestring with a postgis query.


2. After that I created a distance matrix with Raster/Analysis/Proximity in QGIS.


3. Finally I created an aspect raster from the output raster.

Is the red line really the "center line" between these two linestrings?

Is there a more efficient way to do this?