How can I turn all features of my polyline (postgis and/or shapefile) into one direction - it doesn't matter what direction. I know how to switch the direction of lines but I have no idea how to bring all lines (I have thousands of them) into one single direction.
A line can have only two directions, the one or the other like 0 or 1. I want them all to have the direction 0 OR 1. For example the left line in the image is in direction 1 the middle line is in direction 0 and the right one is in direction 1. Now I want the middle line to direction 1 OR the right and left line to direction 0. So that all lines have the same direction 1 OR 0.
geom;given_direction;wanted_direction line;1;1 line;0;1 line;1;1 line;1;1 line;0;1 line;1;1