[HOT] Comment to project managers of Building projects

john whelan jwhelan0112 at gmail.com
Wed Dec 27 19:10:46 UTC 2017

A snapshot of 10% of Uganda gave me 870 duplicate buildings. This is where
two buildings overlap by more than 50%. This is merely to give you an idea
of the scope of the problem.

If you are relying on the data then running Mike Thompson's detect building
script will find any duplicates in your project.

Typically I'm seeing clusters of up to 200 duplicate buildings in a small
area, that one was on a project to count buildings for a solar panels.
These are not uploaded twice but the buildings have been mapped twice with
small differences.


Select Duplicate Buildings
Selects duplicate, or near duplicate, area buildings in JOSM's active
A "near duplicate" is a building whose area overlaps another building's
area by more than 50%. Only the first building encountered of an
overlapping pair is selected. This is done so the issue does not have to be
looked at twice. The selected buildings are added to the current
Currently only works with buildings that are ways (not multipolygons).

To Run:
* Install JOSM's Scripting Plugin (only necessary once)
* Place file in a convenient location on your system (only necessary once)
* Click "Scripting" (on top menu bar)
* Click "Run"
* Click "..." button and select the script file.
* Click "Run"

If you decide to delete some I'd recommend downloading the area fresh in
JOSM then running the script, inspect each building deleting if need be
then upload the results quickly to reduce the risk of a another mapper
deleting the other building of a pair.

Cheerio John
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