How to deal with orphan nodes in OSM?

This is a guest post by one of our Map Analyst team interns, Manuela.


While editing the map I stumbled upon clusters of orphan nodes. Basically, orphan nodes have no tags and are not part of a way. One example here:
nodes

Some online tools report these as bugs/issues (e.g. osmose). You should be careful, though. These may have been created with a reason. Before proceeding to deletion, ask yourself:

  • Were these nodes orphan from the very beginning?
  • Is there just one orphan node in a changeset or are there many?
  • Are they arranged in a special way/shape?

If so, they may be GPS traces that could be used for mapping. And still, even nodes from GPS traces should be deleted, there is no reason to keep orphan nodes in the map AFTER you extracted all the needed information from them.

My advice: research! There are many tools to find out the history of an OSM element. To name a few: object history, WHODIDIT, OSM History Viewer, attic data etc.

You’ll probably find yourself in one of the following situations:

  • You’ve found a newbie that creates orphan nodes by mistake
  • The nodes are correct but the user forgot to add the tags
  • A Redaction bot deleted ways without deleting the corresponding nodes (read more here)

Your options:

  • Contact the creator or the used who made the last change via a changeset comment or private message (in a friendly way, of course)
  • Add relevant tags if that’s the case
  • Delete the nodes or leave a fixme tag for other users that may know the area better than you

How to find orphan nodes

Osmose will report orphan nodes clusters as issues:

orphan

In JOSM, orphan nodes (even isolated ones) can be easily found using the Search tool, with the following queries:

type:node tags:0 -child

or

type:node untagged -child

The -child tells JOSM to select only those nodes that are not part of a way.

As if that wasn’t enough already, I’ve created a map paint style that highlights orphan nodes and dims other elements. This will help you analyze the distribution of the orphan nodes without needing to select them and will help you take the decision to delete or no.

This is the default JOSM map paint style, where you can’t really see the orphan nodes that well.
orphan2
This is how the map looks like after applying the new paint style.

If you want to use this map paint style, you can find the script and a step by step guide on the GitHub page:

https://github.com/manuelabutuc/JOSM-Orphan-nodes-map-paint-style/tree/master

Have fun spotting orphan nodes! But remember to delete them only if you are sure they have no reason to be on the map. If you have any improvement suggestions for this map paint style, feel free to comment below or fork the project.

 

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Author: mihai

Get in touch with me at twitter.com/ubermih