[mkgmap-dev] Splitting at country borders?From Carlos Dávila cdavilam at jemila.jazztel.es on Sun Sep 20 00:37:47 BST 2009
Apollinaris Schoell escribió: > On 19 Sep 2009, at 4:29 , Johann Gail wrote: > > >>> So is it possible to configure the splitter do split the maps not >>> after >>> x-Number of nodes but at these coordinates? >>> >>> >> No, this is not what I have written. There is some missunderstanding. >> The recent splitter is not able to split at geographical boundaries. >> This is the task of osmosis. >> > > even osmosis can't do that. osmosis takes a polygon as input and > doesn't read boundaries from osm files > > > >> Maybe it is not too complicated to build this feature into splitter, >> but >> at the moment it doesn't. >> > > neither splitter or osmosis insert new points. but it is required to > have boundary nodes in mkgmap. splitter would need to calculate > crossing points with the boundary or a provided split polygon with all > ways and insert the boundary points. > > >>> Or is it posilbe to do a presplit, which creates a tile for each >>> country >>> and then in a second step splitting the country files? >>> >>> >> Yes, this way should work. But for the presplitting you can't use >> splitter. I don't use osmosis by myself, so I don't know internals of >> it. But I know, that geofabrik splits its regions with osmosis. >> > > you can do the presplit but routing can't work then across boundaries. > osmosis has different modes > - clip ways at the boundary -> no routing across tiles due to missing > nodes > - include the whole way -> long ways extend far beyond the boundary, > areas aoutside the boundary will be incomplete, tiles will overlap in > huge areas. routing may break in these overlap tiles > - don't clip the way but omit the points outside the box/polygon -> > combining 2 osm files should work. but then why did you split them? > > > > >>> Then it would be possilbe to download europe from geofabrik, split it >>> into countries and then crate maps from it. >>> These maps would be interroutable. It would be also need less >>> computing >>> power/memory for doing this compared of >>> processing the whole europe map >>> >> I would expect the interstate routing to work. Precondition is >> obviously >> that the presplitted tiles don't miss any segments at the border and >> the >> border nodes have exactly the same coordinates. >> >> > > still don't understand why this is useful. If you want multiple > countries and route across countries and tiles why split it more than > necessary and try to assemble again? > If I understand right your question, I can give you a reason. I build maps for Spain, Portugal and South of France. If I could combine Geofabrik osm files so that routing would work, it would be much faster to download individual country files (~300 MB altogether), assemble them and split the resulting file with splitter than download all Europe (2 GB->30 GB uncompressed) and processing such a big file to get my area of interest. Regards Carlos > >> Regards, >> Johann
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