[mkgmap-dev] splitter r232

Fri Nov 16 08:09:35 GMT 2012

Hi all,

> 
> 11000004: 1800192,1406976 to 1968128,1681408
> 
> In this tile (north-western Turkey) there are missing two ferry-routes 
> (Yalta-Istanbul and Sivastopol-Istanbul). As I opened the tile in josm, 
> I discovered also, that there are several objects in that tile, which 
> shouldn't be in it. Eg. boundary of USA, Russia

reg. the ferry-routes:
I can't say for sure, but I'd say these ferry lines really don't cross the tile.
I think it is a good idea to write the tile bordes in gpx format, this will help
to answer such questions. 

reg. "objects that shouldn't be in it":
I would accept Russia for now, but USA really sounds strange. 
I think the reason is the very simple  that is used now:
For a multipolygon (or boundary), splitter simply calculates the bounding box
of all ways. The result is a rectangle. Every tile that intersects this rectangle  contain the 
complete relation.
The advantage of this method is that splitter doesn't have to calculate the real MP (which 
invvolves many special cases like incomplete data, holes etc). I wanted to leave this
to mkgmap.

For most boundaries, this simple alg. works quite well, because the bbox of the boundary doesn't
contain too much other stuff.
The bbox for Russia is obviously very big and contains a large area which doesn't belong 
to Russia. A real problem is USA (and probably other countries with external territories: 
Because of Hawai and some other islands the bbox for USA covers almost half of the planet.
I hope I can find an alternative algorithm that is still simple and fast, but doesn't
make this error. 

> 
> Also josm reports several errors because not all nodes of some ways are 
> in that tile. Maybe this could cause the problem of missing ferry-routes.

This is caused by an error in splitter and wiil be fixed soon.

Gerd

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