Hi Johann,
Hi Mark,
if your guess is true (it indeed seems so), then this would mean that there is some linking between the graphical line and the arc. I know there is a one to one link at highest resolution. There seems to be link at lower resolutions too.
This may well be the unknown reason for the improving of the routing with the merge-lines option.
Perhaps, but that is a mystery to me.
What I do not understand: How can I link a long line to a lot of arcs. There must be a way, as the original garmin maps contains long lines too. Are there some arcs for lower resolutions too?
So far, I have not seen any evidence of that. What I have seen in some maps created by cgpsmapper is what I call "short-circuit arcs". These are extra arcs that jump over some of the points in the way to make a more direct route. Here's some ascii art that illustrates what I mean: ---------SCA--------- | | -----A++++B++++C++++D++++E---- | | | | | | The + signs show a single road that has nodes A-E. Nodes B, C and D have other roads connected to them. A and E are connected to other ways but they also have a short-circuit arc (SCA) between them. I have seen short-circuit arcs span from one end of a road to the other and also from an inner node (like B, C or D) to one of the ends. Note that the short-circuit arcs don't span roads, they just connect nodes within single roads. I have been planning to do some experiments to get to understand this more but have not found the time to do so yet. Cheers, Mark