potlatch creates invalid ways having only one node or multiple consecutive identical nodes

[openstreetmap-trac]

Reporter: xylome
[Submitted to the original trac issue database at 12.11am, Wednesday, 25th November 2009]

• a way with only one node makes no sense: http://wiki.openstreetmap.org/wiki/Data_Primitives#Way

• a way can have identical nodes (e.g. circular ways), but there is no reason for having an identical node succeeding itself within a way.

please refer to the history of the ways in changeset http://www.openstreetmap.org/browse/changeset/3210744. in almost all cases potlatch was the editor in question generating those errors, before xybot repaired the errors.

[openstreetmap-trac]

Author: Richard
[Added to the original trac issue at 1.33pm, Tuesday, 22nd December 2009]

Steps to reproduce please or I'll close this.

[openstreetmap-trac]

Author: xylome
[Added to the original trac issue at 1.23pm, Tuesday, 26th January 2010]

this is a serious issue, please investigate this further!

i don't have the slightest idea how this could be reproduced (i'm using JOSM as editor), but there are hundreds of those ways produced each day.
see the changesset of xybot http://www.openstreetmap.org/user/xybot/edits "removing multiple consecutive identical nodes in ways/delete one node ways" as a reference!

[openstreetmap-trac]

Author: Richard
[Added to the original trac issue at 1.48pm, Tuesday, 26th January 2010]

Replying to [comment:2 xylome]:

i don't have the slightest idea how this could be reproduced (i'm using JOSM as editor)

Then I would ask you to open Potlatch for once in your life, and try. I have a million and one people asking me to do things; if you want your particular itch scratched then you'll need to at least do a bit of the work yourself.

[openstreetmap-trac]

Author: xylome
[Added to the original trac issue at 12.39pm, Thursday, 28th January 2010]

let me first say, that i appreciate your work very much and that potlatch does a very good jobs in giving people a jumpstart into osm.

but it's not an itch of mine and yes i have no idea how this erroneous behaviour can be reproduced. i'm only seeing the results. it's a data integrity problem potlatch is producing here.

maybe you could do a validation of the ways potlatch produces before they get uploaded.

[openstreetmap-trac]

Author: Richard
[Added to the original trac issue at 12.55pm, Thursday, 28th January 2010]

That's kind of the problem, though - as far as I know (I haven't looked at that code for a while) Potlatch does validate this. There's a method in way.as called removeDuplicates that makes sure that if, for example, you have a way ABCB and C is removed, one of the Bs will be removed too. This is why I'm keen to get a reproducible test case.

[openstreetmap-trac]

Author: xylome
[Added to the original trac issue at 1.28pm, Thursday, 28th January 2010]

for me it seems as if it happens, when people try to doubleclick to end drawing a way. most of the multiple identical nodes are on the end of a way and do not seem to be the result of a deletion of a node in the middle of a way.

[openstreetmap-trac]

Author: xylome
[Added to the original trac issue at 1.32pm, Thursday, 28th January 2010]

some of the ways are one-node-ways. it seems as if the user deletes one node of a two-node-way. the result should be, that also the affected way should be deleted then. the last remaing node should also be deleted if it is no member of another way or relation.

[openstreetmap-trac]

Author: Richard
[Added to the original trac issue at 1.43pm, Thursday, 28th January 2010]

The hint about it being the end of a way is really helpful - thank you. I'll have a look next week once I've got a bit more free time.

[openstreetmap-trac]

Author: Ilis
[Added to the original trac issue at 3.56am, Friday, 29th January 2010]

I have such errors using Potlatch. I dont no steps to reproduce, but it often happens when I have add point on crossing ways with Shift+Click.

[openstreetmap-trac]

Author: katzlbt
[Added to the original trac issue at 11.59am, Sunday, 7th February 2010]

I would bet it can be done by linking the way to itself and deleting the node before.