[mkgmap-dev] Should inter tile routing still work when splitting Splitter results again?

Tue Sep 29 19:04:23 BST 2009

On Tue, Sep 29, 2009 at 6:28 AM, Lambertus <osm at na1400.info> wrote:

> It's a bit difficult to specify a short topic title for this, so here it
> goes:
>
> Goal:
> Render the world with tiles that are as large as possible.
>
> Problem:
> If you split e.g. America in large tiles with e.g. 1.400.000 nodes then
> you end up with a lot of tiles that do not render. If you want
> everything to render then you need to use 400.000 nodes or so which
> results in more then 1000 tiles.
>
>
was able to render all of North America with 90000 nodes. But it's always a
bit of luck. splitter puts in only 50-70% of the limit in a majority of the
tiles. a small change can result  in a very different setup.


> A solution:
> I created a PHP script that splits America with an high initial node
> count (of e.g. 1.400.000) and tries to render each resulting tile. If a
> tile render fails then that area is split again with an ever lower node
> count until at least two subtiles emerge which are then rendered. This
> process continues recursively until all tiles are rendered or the node
> count gets too low and splitting is aborted.
>
> The result:
> Neighboring tiles sometimes overlap because splitter seems to use a
> little larger bbox for splitting then what the source file contains. You
> can see the result of this on http://garmin.na1400.info/routable.php
>
> The question:
> Will routing be a problem because the result of recursively splitting
> and rendering results in tiles that apparently do not line up perfectly?
> I've done a few tests and it feels that routing has become worse, but I
> don't have a definitive answer. If so, what can be done about this? I'm
> curious if anyone (Chris?) has ideas about it.
>
>
have tried it manually once, the tricky part is to split a tile from
splitter again with splitter, because of the overlaps are required for
mkgmap and can't be removed. but splitter will use the data and construct a
larger bounding box.
You can do it this way. run splitter again on the tile. use area.list to get
the new edge where the tile is split and combine it with the definition of
the large tile in the area.list from the first run to get the outer
alignment with other tiles from the 1st run. run splitter again with this
new aligned areas.list.
to complicated for me to follow it systematically and went with lower
max-nodes


> I can provide the script to anyone who's interested. Just send me an
> email off-list.
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>
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