Hi Steve/anyone, Can someone please clarify exactly how DivisionParser.round(Area) is supposed to behave? My understanding is that it is taking the area passed in and rounding the edges *outwards* to the nearest multiple of 0x0800. ie, the area should get a little bit bigger in each direction. If that is true, then I think there are a couple of bugs in the rounding up code, especially when dealing with negative values. Here's the output from some logging I put into DivisionParser.getTotalArea(): details=(41.23698949813843,-73.50664615631104) to (42.888779640197754,-69.93184089660645) minLat=1d52f7 maxLat=1e7faa minLon=ffcbba86 maxLon=ffce454c Rounded bounds=(41.220703125,-73.564453125) to (42.890625,-69.9609375) minLat=1d5000 maxLat=1e8000 minLon=ffcbb000 maxLon=ffce4000 As you can see, the min/max latitudes are both rounding 'outwards' and make the area bigger, as does the min longitude (though I think it should go to 0xffcbb800 not 0xffcbb000). The max longitude is rounding the other way and is making the area slightly smaller. This in turn leads to the following assertion failure (when processing massachusetts.osm with default settings and assertions enabled): Found val=1dc1ce42 lon=ffce4200 left=ffcbb000 right=ffce4000 Exception in thread "main" java.lang.AssertionError: -3259904 at uk.me.parabola.splitter.AreaSplitter.splitHoriz(AreaSplitter.java:101) at uk.me.parabola.splitter.AreaSplitter.split(AreaSplitter.java:74) at uk.me.parabola.splitter.Main.calculateAreas(Main.java:180) at uk.me.parabola.splitter.Main.split(Main.java:95) at uk.me.parabola.splitter.Main.main(Main.java:78) Another potential corner-case is when rounding the value 0 down. Because the check is for val > 0 rather than >= 0, it ends up being rounded down to 0xfffff800 rather than just being left as 0. Is that intended (not that I think that case matters so much)? Assuming my understanding above is correct, here's how I think the rounding methods should be implemented to give the correct rounding in all situations: private int roundDown(int val) { return val >> SHIFT << SHIFT; } private int roundUp(int val) { return (val + (1 << SHIFT) - 1) >> SHIFT << SHIFT; } I've tested this change successfully with several files including massachusetts.osm. What do you think, is it the right thing to be doing? Chris