[OSM-dev] Tiling the Planet and Missing Nodes

[Ben Supnik]

Hi Y'all,

I wrote (yet another) small C program to split the planet XML into 
"tiles".  The only thing that I think is interesting about my tiler (vs. 
the exisging ones) is that it can run the whole planet on a 32-bit machine.*

(Source code is available via the git mirror of the x-plane scenery 
tools - I'll post a link once I have the bugs completely worked out.)

But...it appears that there are cases where a node has been deleted from 
the database while being referenced by a way.

 From what I can tell, this is not a desired condition, but it is 
pervasive due to previous bugs in the OSM software, and there isn't a 
process to "globally fix it" (e.g. delete the way reference, not that 
that would even necessarily be the right thing to do).

 From my last run, way id 4043882 references node 365476284 that is not 
present in the dump.  This is with planet version 090325.  Grep reveals 
that 365476284 is only present in an "nd" tag as part of the ref= 
statement. :-(

My question is: what is the right interpretation of a missing node? 
Should I simply pretend the node reference does not exist (e.g. delete 
the vertex from the way)?

cheers
Ben

* the program uses a multi-pass bounding box algorithm to guarantee _at 
least_ all of the nodes necessary to fully complete ways that might pass 
through a given tile...in other words, it exports a bit too much per 
tile to ensure that nothing is missing - no matter how long the ways.
net.




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