[mkgmap-dev] Missing ways part 1

Mon Oct 18 21:38:12 BST 2010

Marko wrote:
> If I remember previous discussions correctly, splitter does not split
> lines exactly at the tile border, but instead it includes all nodes
> that are not too much outside the tile.

That is also what I understood. Splitter includes in each tile, the
nodes that fall within the tile, and also the nodes in an overlap region
around the tile. The width of the overlap can be set with --overlap.

> An almost-straight long way can be drawn with few nodes. You could
> help the situation by adding a point to the line close to the
> splitting border.

I would expect it to cause a problem, if a particular way does not have
a node in the overlap region. The difficulty with your fix is that it
would only work for me (and only if I use the same areas.list each
time); it will not work for other users. Also, it will not work for me
in the long term, because data is continuously added to OSM, so the
tiles need to be made smaller as time goes on.

As I understand it, splitter is intended to clip ways at the last
included node. [This is done to avoid an additional pass through the
input file.] If there is no node in the overlap region, I would expect
the way to stop short of the bounding box. In the finished map, I would
expect to see a gap in the way at the tile boundary. The maximum length
of the gap would be one segment, between adjacent nodes.

What I am actually seeing is that the way is entirely lost from both
tiles. When inspecting the tiles in JOSM, I can see that all the nodes
are present, including those from the missing way. But few of the nodes
in the overlap region have ways attached. So it appears that splitter is
not working as intended.