[OSM-talk] RFC: what are empty nodes and how should we use them?

[MP]

> > In the IRC channel i was told, that there are users who paint
> > empty nodes in the map to mark things like
> > "road is not mapped, but continues here"
> >
>
>  I do this occasionally, and I'm sure I haven't made this up but got the
> practice from someone/somewhere else - when a way is drawn and you know it
> goes on but haven't mapped it, you put three "dots", just as you do in
> written language:
>
>  ---------------  . . .

I've seen "fixme=road continues" tag attached on the last node of the
way in these cases. Three dots are quite prone to deletion ...

>  I'm not religious about it but I think it is pretty elegant because it does
> not require language to explain it - or at least that's what I thought until
> I heard from several people that they "delete empty nodes on sight" without
> further thought.

I delete them too, but not without further thought. Usually, if the
node is old enough (week or more) then it is not part of some ongoing
import (or the import failed) and I usually delete them. Looking at
the changets in which the node belong help with determining why the
orphaned node is there ...

>  I mean - an empty node somewhere in the middle of town which has sat there
> for ages, ok, but if you saw something like the above, where the three nodes
> clearly hint at a way continuation - would you really remove them? I'd think
> that a bit careless.

using "fixme=road continues" is more stable solution for marking this
and unlike three dots, this case will show up as warning in validator
- so you can get hint that something needs improvement, in this case
probably a survey or tracing from aerial imagery or whatever. Three
dots are easy to get deleted accidentaly and easy to miss.

>  In fact, I'm going to fix the JOSM validator to detect these cases and not
> complain - it is too easy for people to thoughtlessly hit "fix errors" and
> thus inadvertently remove information.

You will make some specific check for three continuous dots? Well,
there are areas with thousands of such orphaned nodes and trying to
check if there are somewhere three dots in a line in such areas
wouldn't be easy - either the check will be very slow, prone to
errors, or you will need some complex and sophisticated algorithm to
make it at least somewhat reliable.

Martin