[OSM-talk] Potlatch and the destruction of good work (N6 Ireland)

Dermot McNally dermotm at gmail.com
Wed Jul 25 19:33:06 BST 2007

Dear list,

I'm not the first to suffer from this, and it can't be avoided in an
open community project, but I have to add my voice to the others
recently who have complained at the great ease with which an anonymous
user (who it's hard to ask to stop) can cause damage to the existing
data set that's difficult to reverse. A few ideas have been advanced,
including read-only tagging, undo capability for Potlatch or even a
formal way of reverting back to earlier data when it gets clobbered.

This particular case centres around a section of the N6 road in the
Irish midlands. A while ago, I created and tagged most of this road,
in places using unwayed segments from other users or their GPS trails,
in places using my own trails. Today I discovered that somebody
unidentified has been using Potlatch to draw the road alignment of the
replacement N6 scheme that's still under construction and isn't at all
visible on the low-quality Yahoo images of that part of Ireland. This
way was then tagged as the main road (it won't be open for at least a
year), the actual road retagged as secondary and a few nodes pulled
madly out of place in the process (no undo=no easy way for the mystery
mapper to fix things once deselected).

Personally, I'd favour a world where you can't edit anonymously, at
least using Potlatch. Right now, I don't know who did this or what
bits of the map he might alter next. What would ideally happen here is
that we'd get talking and support each other's efforts, based on
consensus about the correct approach. In practice, all I can do is
post here and hope he's on the list. (if so, please map yourself

My ideas for improvements in no particular order:

* All Potlatch edits tagged with username, method of generating email
to named user.
* All edits tagged with username (how else can you enforce community spirit?)
* Anonymous editing still possible, but not alteration of existing ways or nodes
* A read-only flag that we can lay down on data we consider stable,
switchable by editors but fulfilling a "safety catch" function
* UNDO FOR POTLATCH!!! (OK, I lied about the lack of priority)

The alternative to safeguards against rash edits is for us all to keep
copies of all bits of the map that we've touched, and even then, in a
densely mapped area, restoring broken stuff will be very difficult. We
need to work out how to manage with "too many cooks".

Finally, I need some advice on how to go about fixing things without
causing further strife. Somewhere out there is a mapper who thinks
it's valid to tag a roadway that doesn't exist yet. I could take the
counter-position and simply wipe it, but that invites him to put it
back again and maybe break more of the existing data in the process.
Not good.

However, if the alignment he created really is based on, say, true GPS
trails from the construction site, it would be useful to keep the way
for use once the scheme is complete. Is there a precedent for tagging
a road under construction?

Opinions welcome.

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