Hi Guys, Frederik, thanks - I am stupid...I found your code shortly after my post...should have Googled first!
Number 9 was the main item I was concerned about...e.g. I can't _quite_ be sure about data integrity if a node might not be present in all tiles that contain ways that reference it. Most of OSMCut looks very similar to my algorithm...the main differences are that I was looking to: 1. Use bounding boxes - bounding box of a way is union of bounding box of nodes, and then the bounding box of the nodes is grown by the union of all ways that reference it. This takes a few linear passes over the data, but should theoretically give me all of the nodes I need. (And probably a bunch of others I don't care about.) 2. I was looking at using a sorted array for nodes rather than a hash table...log-time lookup might be too slow though... Shaun - my end goal is virtual world modeling of the entire planet, and the tool the data is destined for is 1x1 degree tile based. I think after splitting into "rough cuts" I'd use something else (GRASS or code based on CGAL) to cut down to true 1x1 clipped tiles. Frederik, let me see if I can modify osmcut to use bounding boxes*...this would let me output nodes to _every_ tile that needs them (as well as, probably, a bunch of tiles that don't, if ways are huge compared to tiles). cheers Ben * My bounding box scheme also makes assumptions about the tiling scheme, but then if osmcut has to open a file descriptor per tile, your assumptions and mine are quite similar. :-) Shaun McDonald wrote: > > On 4 Dec 2008, at 23:18, Ben Supnik wrote: > >> Hi, >> >> Andras and I were looking at cutting the OSM planet file into 1x1 degree >> tiles (including at least enough nodes outside the tile to correctly >> "chop" a way at the tile boundary). >> >> I think I have an algorithm that can do this in four passes over the >> planet file on a 32-bit machine, using perhaps 2-3 GB of RAM. >> >> Before I go forward...am I reinventing the wheel? I know that osmosis >> can do this kind of thing, but my understanding is that it extracts a >> finite number of "streams" from the data...we actually want to take all >> of the data and split it into 64800 parts. >> >> If no one has something like this and I can get it working, I'll post >> the code somewhere. :-) >> > > What is the end use case of splitting the data this way? > > Are the current country (or in the case of the US, state) extracts not > suitable? > > Shaun > > -- Scenery Home Page: http://scenery.x-plane.com/ Scenery blog: http://xplanescenery.blogspot.com/ Plugin SDK: http://www.xsquawkbox.net/xpsdk/ X-Plane Wiki: http://wiki.x-plane.com/ Scenery mailing list: [EMAIL PROTECTED] Developer mailing list: [EMAIL PROTECTED] _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
