Missing Maps Mapathon Quality Report

Mapathon

Sample City Mapathon

Project

When

2026-01-01 09:00 → 2026-01-01 13:00 (UTC)

Mappers

47 contributors

87%

586 objects came out clean — great mapping!

13%

84 objects have a little room to grow

from 3 mappers

A few things worth a second look

Nothing alarming here — just small tweaks that'll make the map even better.

Check	Issues	Notes
Buildings tagging	22	Buildings tagged differently than building=yes.
Overlapping buildings	14	Buildings that geometrically overlap or are contained within another building (each count = one pair). 3 building(s) were duplicated.
Building outlines that cross a highway	6	Building drawn through an existing highway.
Non-orthogonal buildings	31	Rectangular buildings that most likely should be orthogonal with squared corners.
Buildings with layer tag	9	Buildings tagged with layer=* created as recommendation from iD editor when two objects are overlapping. The correct solution is for the objects to not overlap.
Buildings with shared nodes	12	Buildings sharing at least one node with another object (each count = one shared node, not a pair; 8 building(s) affected).
Untagged objects	15	Nodes and ways with no tags, most likely mappers forgot to add a tag such as building=yes.

Quick reminders to make next time even smoother — you've already got the hang of it!

Use building=yes for all buildings
Unless the project instructions say otherwise or you have local knowledge of the area you are mapping.
Don't draw a new building overlapping an already existing one
Try to draw each building separately. Zoom in and look for outlines already drawn in the area before tracing a new one.
Do not draw buildings over highways
Building outlines should sit beside highways, not on top of them.
Square building corners after drawing
Press “Q” in your mapping editor after drawing a rectangular building outline to straighten the corners. If mapping in JOSM, use the buildings_tools plugin which draws rectangular buildings automatically.
Avoid using the layer tag on buildings
When iD editor warns about overlapping objects it suggests adding layer=*. The correct fix is to move the object instead so it does not overlap, not to add a layer tag.
Do not snap buildings to highways or other buildings
Each building should have its own independent nodes. In iD editor hold “Alt” (“Ctrl” in JOSM) to avoid snapping to existing nodes. If you accidentally connected nodes, use “D” in iD editor (“G” in JOSM) to unglue them and then adjust their position.
Always add tags to the nodes and ways you draw
A node or way with no tags has no meaning in OpenStreetMap. If you drew a building outline, make sure to add building=yes before saving; if you placed a standalone node, tag it appropriately.