[OSM-talk] conclusions from my postgres / postgis experiments

[80n]

On 11/23/06, Robert (Jamie) Munro <rjmunro at arjam.net> wrote:
>
> raphael Jacquot wrote:
> > here's what I found during my little^Wextensive experiment:
> >
> > 1) we have tons of duplicate segments
> >      ((s1.from = s2.from) AND (s1.to = s2.to)) OR
> >      ((s1.from = s2.to) AND (s1.to = s2.from))
> > 2) we have 4000+ degenerate segments
> >      (s.from = s.to)
> > 3) we have ways with no segments
>
> Can we just write a script to delete them (except for case 1 where the
> segments appear inside a way)? Database rules should be applied to make
> sure they can't happen again. This may necessitate moving away from
> MySQL. :-)
>
> > 4) we have degenerate ways where the way is neither a proper linear
> > feature nor a proper closed polygon, but rather an unwidedly spaghetti
> > monster. most of those furthermore involve a loop of some sort...
>
> These should be allowed. For rendering, I would suggest the following
> algorithm:
>
> * Go through the segments in the order they are in the DB.
> * add all the segments until you reach one that doesn't start where the
> last one ended.
> * Use what you have at this point to decide where to put the road name
> etc.
> * Add the other segments
>
> That way, people can control where the road name will be rendered on
> split ways by making sure that the segments that want to share the name
> come first in the list. By default, editors should try to find the
> longest path and put that at the start of the list. It would be nice if
> josm could display this information somehow (little numbers next to
> segments when a way is selected, maybe), and have an easy way to reorder
> segments in ways, either automatically or manually.


This is a very good and constructive proposal.  We certainly need some rules
like this to make sense of non-linear ways.

80n


Robert (Jamie) Munro
>
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