[mkgmap-dev] [PATCH] Splitter area rounding seems wrong

Tue Aug 30 16:58:28 BST 2011

Hi

> 1. If the goal is to shift the boundaries onto a coarse grid, why round
> *down* for longitudes and *up* for latitudes? Why not round in the same
> direction for both?

Even though I made that change (originally it rounded down/up in the
same way as your patch). I have no idea why one goes up and the other
down! Probably no good reason.

> Finally, I am wondering how important the rounding is. It seems that
> mkgmap will happily process arbitrary .osm files, including those that
> never passed through the splitter and thus do not have rounded
> boundaries. Would it be possible to leave out the rounding? Or is it
> needed for inter-tile routing for example?

For routing to work across tiles the nodes at the edge of the tile
must match exactly (or within a few units at least) the edge node
of the same road in the adjacent tile.

The page: http://www.mkgmap.org.uk/page/17 gives some background on
the original design.

The point about rounding to the course boundaries is not true from the
point of view of the Garmin format.  At the time I didn't know how to
make it work without putting them on course boundaries, but now we
probably could.  In general the tiles can have completely arbitary
boundaries that follow a country border for example, but this would
need corresponding support in mkgmap.

..Steve