[mkgmap-dev] Commit: r766: Write more of the *.mp-data.

Thu Dec 4 15:31:22 GMT 2008

Hi,

On 12/4/08, Robert Vollmert <rvollmert-lists at gmx.net> wrote:
> Hi Alex,
>
> thanks for your help!
>
> On Dec 4, 2008, at 13:44, Alexander Atanasov wrote:
> > On 12/4/08, svn commit <svn at mkgmap.org.uk> wrote:
> >
> > > what it does. The road class from RouteParams is set in various
> > > places, not really sure they should all get the same. (Why is it
> > >
> >
> > They shouldn't be the same. Some ascii art:
> >
> > ----------------TRUNK ROAD------L----------------
> >  -- local neighborhood streets -|
> >  |---  --- many small streets --- |
> >      \
> > -------L-  OTHER TRUNK ROAD ----------------
> >
> > The small streets should be class 0, TRUNKs class1, etc.
> > highways class 6.
> >
> >
> > >
> > > > From the small streets you have links to L, how to get on the
> > > >
> > >
> > next road class /i'm not sure but highway herarchies sounds like this/
> >
>
> Right, the streets come different classes. I'm currently writing this
> class in three places:
> NOD 2: the first byte is class and speed and two unknown bits (once per
> road)
> Table A: one byte is class and speed and oneway and toll (once per arc)
> Arc: the destination class (this must be wrong)
>
> For the moment, we're not writing any links. I assume well-placed links
> would just optimize routing, but it seems to work without.

Links are helpful for fastest route, for shortest may be not.
Does the routing work in both modes as expected?

>
> Are links only ever between nodes on the same road, or can they go further?
> Say
> A--1--B--2--C
> where A and B are nodes in a residential area, 1 and 2 are different small
> streets, and C is on a trunk road. Can there be a link A->C?

Have to verify this but afaik they are on the same road.
Pointers to the nodes that connect to higher road class.
So if 1 and 2 are different roads, there is a link to B then to C.

> >
> > > "destination" class in an arc?)
> > >
> >
> > That's for reading. If you are on node class 5  skip nodes with class < 5.
> > The graph is searched bidirectional. Start from pos and dest and try
> > to go to a bigger road class. At some point they meet each other.
> > In other words when you get on the highway stay there, don't route along
> > residental streets.
> >
>
> The class of a node is the maximum of the classes of the roads
> it lies on? And the destination class of an arc/link is the class
> of the destination node?
>
> That makes a lot of sense, but I remember seeing some maps where this
> didn't seem to be the case.

There is a class of the road in net, i think the destination class should be
derived from that class.  You can reach a node via different arcs with
different classes. Node's class itself makes sense only when starting
to route from that node, iirc it was always 4 in the cgps compiled
maps.

-- 
have fun,
alex