1. Gardening OSM data with Overpass API
Roland Olbricht
at SOTM 2016 in Brussels

2. Introduction This talk is about This talk is not about
Support for the DWG
Tracking changes
Precise and brief
data presentation
Answer question:
„Is there vandalism?“
Tag A → Tag B systematically
Blaming user
Blaming tools
Heuristic guesses

3. Tools
to screen changes

4. Changeset driven tools
Just Bboxes -
for a day
already too much
OSM History Tab

5. Bbox + Comment for a single changeset
Changeset driven
tools
OSM Changeset View:
Bbox + Comment for a single changeset

6. Achavi: all object changes https://overpass-api.de/achavi/?changeset=
Changeset driven
tools
Achavi: all object changes

7. same functionality as Achavi
Changeset driven
tools
OSM History Viewer:
same functionality as Achavi

8. 1st problem: Pogostick Navigation
History
tab
Comment A
Comment B
bad
comment
or bbox
bad
comment
or bbox
Changeset
view
Chgset A
Chgset B
no action
required
no action
required
Achavi
Changes in A
Changes in B

9. 2nd problem: too much details
Which of the 870 objects
need attention?

10. 3rd: Achavi: sometimes wrong?
new shape
old shape
way unchanged
since 2014?
Ways
need a timestamp
for geometry

11. large relations everywhere
4th problem:
large relations everywhere
A 500 meter big bbox ...
… is often affected by 500 km sized relations

12. object history by version delta
Object driven
tools
Mapki's Deep Diff:
object history by version delta

13. Object driven tools: problems
1. Way too many objects to screen
2. May miss changed geometry
unchanged
after 2014?

14. find tiles with changed nodes
Timeline driven
tools
Who Did It:
find tiles with changed nodes

15. Who Did It: problems It is Types of change for a way for nodes only
Unchanged
Geometry
Version
Not easy to fix:
Ver. + Geom.
Topology
Tags
Members
Tags + Geom.
Everything

16. Ideas for
Solutions

17. Solutions Changes in long open changesets are clustered
→ Split changesets into clusters

18. Solutions
Topology
(needs routing)

19. Solutions Changeset Impact inspiration: git blame
(lists for each line of code the original author)
clear: tags
unclear: geometry
harder: topology

20. Screening?
Works Now
set date
name deleted?

21. Screening?
Works Now
object deleted?

22. Screening?
Works Now
scroll further ...

23. Screening?
Works Now
Ask user for tagging schema
not wrong,
but never seen before

24. Screening?
Works Now
probably a mistake...
suspicious name

25. Screening? Screen a day of Brussels' edits wihtin 10 minutes
Works Now
Screen
a day of Brussels' edits
wihtin 10 minutes

26. Thank you for your attention