[mkgmap-dev] [PATCH] turn restrictions - alpha code for testing

Tue Feb 24 10:11:18 GMT 2009

Hi Alan,

> > Does that make sense?
> 
> Thanks for the suggestions.  They do make sense, although a part of me
> thinks that it doesn't quite "feel" right.  Another argument for
> making the centrepoint a node rather than a way is that the traffic
> lights at either end of the way are synced together.  For all intents
> and purposes, it _is_ a node, albeit a long, thin one.
> 
> Despite that, my preference would still be to leave it as is, for the
> time being.  I think that we should aim to make the map data correct
> in the first instance.  If there is a problem with routing on a
> particular (brand of) GPS, then that can be broached separately.
> Others may disagree.

Well, "correctness" is in the eye of the beholder. People have
different agendas and expect different things from the map. In this
situation there is a conflict between the visual look of the map and
the need to express some constraint about how traffic may be routed.

It seems to me that the main cause of this particular problem is the
lack of support in the garmin for restrictions of the form: "don't go
to point X if you came from point Y". As far as I am aware, it can only
cope with "don't go to point X if you came from point Y via point
Z". Where X, Y and Z are all adjacent (no other nodes between them).

So, for the garmin, I am not sure that restrictions that have a Way for the
'via' member can ever be supported. Put it this way, if I knew how to
implement it, I would do it anyway even if it wasn't actually very useful.

Cheers,

Mark