[mkgmap-dev] Remove short arcs

Thu Jan 17 18:54:20 GMT 2013

Hi Felix,

I am not sure if I got that right. You use  --remove-short-arcs=5.4
and you say that routing was broken unless the way was longer than 5.4 ?
That sounds to me like the problem that I've described here:
http://gis.19327.n5.nabble.com/short-roads-with-two-nodes-tp5744911.html

Gerd

Felix Hartmann-2 wrote
> On 17.01.2013 16:01, Gerd Petermann wrote:
>>
>> reg. test data: I did not yet try to understand why a short arc brakes
>> routing. I assume it is because you can't calculate the bearing with
>> an appropriate precision?
>> I just know that I see error messages like "road ... contains zero 
>> length arc at ... "
>> or "road ... contains consecutive identical nodes at ... "
>> when I omit the removeShortArcs call.
>> So, I'll try to run the first version of the patch against many tiles
>> and see what happens. If I don't find a problem in Europe,
>> it is likely that we don't need iteration.
>>
>> OK?
>>
>> Gerd
>>
>> >
> 
> The reason As far as I can remember is that if we have the following 
> situation
> 
>     #
>     #
>     #
> --- O UUU ---
>     #
>     #
>     #
> 
> Now consider both # and - U and O stand for streets. O must not be 
> shorter than the routing resolution (which is twice the minimal distance 
> we can put points), else O will be unroutable.
> I found out about it, by having a very short stretch of a road on a 
> bridge, where directly after the bridge (or was is actually sharing a 
> point with the bridge?) a crossing pops up. As soon as we made sure that 
> O is ~5.4m the routing worked again.
> 
> Im not sure if
> 
> --- UUU --- with UUU being shorter than 5.4 works though. (UUU being e.g 
> a bridge).
> 
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