[GraphHopper] Disconnected areas

[Ludwig]

Thanks for the reply.

Just so that I understand the trade-off: basically, the intention is to
exclude areas that would not allow a meaningful routing anyway (apart from
its own subnetwork) and the price to lower this value is a size question
for the resulting routing files?

I am not really familiar with the routing algorithm, I am just amazed that
it works so well and so fast!

I think having the value configurable is a good stop-gap.

Thanks again, great work.

Ludwig






On 24 September 2013 15:45, Peter K <peathal at yahoo.de> wrote:

> Hi Ludwig,
>
> > Hi Peter,
> >
> > fiddling with that parameter seems to do the trick. I managed to get
> > routing to work for Naxos with a value of 500, but had to drop this
> > further to 200 to get routing on some even smaller islands.
>
> Good and bad ;(!
>
> > For me at this point the question is what the motivation is to exlude
> > certain areas at all. Even if this was a private area (behind a
> > barrier) why exclude it from roiuting?
>
> Because you won't find a route if one coordinate of the route is inside
> and one is outside. E.g. if you would search 'Dresden' (or a lot more
> locations like 'moskau' etc) the GPS coordinate would be exactly within
> such an area and you won't find a route. Also routing within
> private/restricted/forestry areas is in my opinion not really useful for
> a public site. Additionally there are OSM bugs which leads to those
> subnetworks.
>
> Do you have another idea? One could try to solve this via a changed
> routing or location-lookup but this looks ugly to me.
>
> I've lowered this value to 200 and made it configurable via
> prepare.minNetworkSize:
> https://github.com/graphhopper/graphhopper/issues/86
>
> Regards,
> Peter.
>
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