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[mkgmap-dev] Splitter feature request

From Carlos Dávila carlos at alternativaslibres.org on Wed Dec 6 18:29:08 GMT 2023

Hi Gerd,

As this new feature would be for areas.list passed to splitter, I 
thought it could assign objects to tiles (inlcuding L-shaped ones) in 
one step, assuming it can do so once it knows the area of each tile, but 
I'm probably wrong, as I don't really know how splitter works internally.

Right/left hand drive side driving is quite difficult to solve in land 
borders, but L-shaped tiles can help avoiding the need of tiny tiles in 
those areas. For areas with a lot of islands, where some drive on the 
right and others on the left, L-shaped tiles would really help.

El 6/12/23 a las 12:23, Gerd Petermann escribió:
> Hi Carlos,
> since nobody else reacted:
> I wonder in what situation an L-shaped tile could be the result of a split-process.
> Do you think about some kind of post-processor which would recombine 2 or more tiles so that they still don't
> reach the maxnodes boundary? Thinking about the way how a split is done, I think it can happen that the combination of two connected tiles are still below the limit,
> but I would assume that an L-shape is rather rare.
> Anyway, if splitter would write non-rectangular tiles we need
> a) a further output file (or a new output format) to store the tile-boundary for input in mkgmap
> b) some new logic in mkgmap to cut ways and polygons along that boundary
> It might be easier to implement b) when boundary lines are only horizontal or vertical, but I am pretty sure this wouldn't solve most of the problems
> reg.  right/left hand side driving.
> ciao
> Gerd
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Carlos Dávila <carlos at alternativaslibres.org>
> Gesendet: Sonntag, 3. Dezember 2023 12:26
> An: Development list for mkgmap
> Betreff: [mkgmap-dev] Splitter feature request
> Hi all
> I usually let splitter decide tiles based on max-nodes value, but for
> some maps I need to supply splitter an areas.list file which I adjust
> manually. Reasons for that include reducing the total number of tiles,
> avoiding cutting of some islands and separating right/left hand side
> driving areas or reducing number of tiles with both sides driving. For
> these cases, it would be helpful to be able to build "L shaped tiles",
> as in the attached image. I think these tiles could be defined by three
> coordinates (A,B,C), which would define the two rectangles in which the
> L shaped tile can be split, and a switch (1,2,3,4) to determine de
> orientation of the "L".
> 1: tile = A-lat, A-lon to B-lat, B-lon + A-lat,B-lon to C-lat,C-lon
> 2: tile = B-lat, A-lon to C-lat, C-lon + A-lat,B-lon to B-lat,C-lon
> 3: tile = A-lat, A-lon to B-lat, B-lon + B-lat,A-lon to C-lat,C-lon
> 4: tile = A-lat, A-lon to C-lat, B-lon + A-lat,B-lon to B-lat,C-lon
> This raises several questions. First of all, if is feasible, then if it
> is worth the effort to implement it, how would if affect splitter
> performance and if it makes sense for other users. Perhaps it could be a
> first step towards irregular tiles...
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