[mkgmap-dev] Re: consecutive identical points

Wed Dec 10 13:45:26 GMT 2008

On Dec 9, 2008, at 14:39, Steve Ratcliffe wrote:
> On Tue, Dec 09, 2008 at 02:11:55PM +0100, Robert Vollmert wrote:
>> Another possibility: MapLine.setPoints occasionally gets passed
>> consecutive identical points, I assume from rounding to the same
>> coordinates. I think they're being written as zero deltas, which I  
>> could
>> well imagine throwing MapSource off. How going through GPSMapEdit  
>> would
>> fix this, no idea.
>
> There is supposed to be code to skip zero deltas in LinePreparer.   
> This
> is because even if its ok at high zooms at lower ones, zero deltas
> will start to appear (althogh there are supposed to be filtered out  
> earlier
> on too).

Right, found it now. There's still possible problems:

1. The effective number of points could drop below two, even though  
there's a check for at least two points initially. Though from what  
Alex said about one-point segments, we may want to allow that anyway.
2. If coordinates in the .mp-file are rounded to the same point in map  
units, this might still confuse the routing graph, since we'd create  
different routing nodes at the same coordinate. There's then also the  
possibility of arcs with length zero. We should probably check for  
this in polish.RoadHelper, though it'd be nice if osm2mp took care of  
that before. Also with the Coord/CoordNode thing, this isn't quite  
straightforward to implement.

Cheers
Robert