[mkgmap-dev] [PATCH] make gps report correct exit when routing through roundabouts

Wed Feb 11 23:09:00 GMT 2009

On Feb 11, 2009, at 23:55, Steve Ratcliffe wrote:
>> The good news is that I *"think"* I have found the data that causes  
>> the
>> problem. Call me sad if you want but I had a spare hour (not) so  
>> using
>> osmosis I started splitting the tile giving the error into 4  
>> quarters. I
>> would run each of these and see if there were errors. I then split  
>> the
>> quarter with errors and repeated the process until I was left with  
>> the
>> attached file. In the bottom left quarter is a tiny roundabout. If  
>> you
>> just move the north node northwards and the south road southwards a
>> couple of feet then the tile runs without errors.
>
> Nicely tracked down.

It turns out my patch above fixes the IllegalArgumentException, though  
I don't really know why, since the roundabout isn't really close to  
longitude zero. Also I don't know if it doesn't break anything else,  
so I'm hesitant about committing it.

> The northmost and the eastmost points on that roundabout are about
> 5m apart and routing nodes have to be more than 5.4m apart.

Do we know why this is? I remember in the length calculation  
discussion that the unit of arc length was 5.4m, but we could just lie  
for shorter arcs.

Cheers
Robert