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[mkgmap-dev] Commit: r1410: Add --merge-lines option to combine lines at lower zoom levels.

From Johann Gail johann.gail at gmx.de on Tue Dec 1 21:08:46 GMT 2009

> My guess is...
> After merging you have 1 graphical line that spans the length of the
> combined lines associated with a routing arc that only spans the length
> of the original un-merged line. When you put the cursor near the lines
> that have been merged, mapsource, finds the arc associated with that
> line and puts the pop-up as close to the cursor as it can while still
> being on the arc. As the arc only spans a part of the whole merged
> line, the popup jumps (away from the cursor) to the end of the arc away.
> It's not really that surprising given the resulting data
> structure that has been produced by the merging.
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.

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?


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