Tracing round buildings - iD editor

The Essentials

Round Buildings

This image keymon shows you which buttons or wheel on a mouse has been used, and which keyboard buttons pressed.

Points to note;

  • Place your points where the walls will reach the ground - 3 points is the minimum. Use the tool to make it round.
  • Make sure you tag!
  • Size matters - population estimates are based on the cumulative building area in a given area,
  • Zoom in enough to see the details - a zoom scale of 20 metres or less is usually about right.
  • Looking for buildings - scan with your scale somewhere between 50 metres and 80 metres. Watch out for shadows and straight lines (round buildings are harder to find!)
  • Buildings and roads, rivers, landuse=residential boundaries or other features should not overlap.
  • If you make a mistake, use the Undo button back arrow to undo your last change(s)
  • We’re all improving the map. If the previous mapper has left the buildings a funny shape or wrong in some way, correct it and consider sending them a polite message.


Round buildings are often found within a compound, and the buildings may be in clusters, or in isolation. It can be difficult to establish if you are looking at a round building or a bush or rock. Buildings are usually found near some means of access such as a path or track, although this can be difficult to see on very hard ground. The vegetation may be worn down by the passage of feet. In some parts of the world the buildings may be on the only dry land, and the access is by boat on a river or lake. There is normally a water source visible within 2 or 3 kilometres of any habitation, but in many parts of the world you do not see the water, but you do see more vegetation to indicate it must be there.

In many places in the world it is easier to build a new village a short distance from the old one, leaving the old buildings to rot away and fall down - sometimes they are destroyed by fire. Look for shadows to help you decide what you are looking at. If all that is left is a round mark on the ground, it will have no shadow. If in doubt add it as a building.

This image shows both a bush and a round building. Shadows can help you to identify if you are looking at a round building, or a bush. In hot climates it is common to find buildings close to trees or bushes which will provide shelter and shade. The instructions to this particular task include a link to a diary entry by someone who has taken photographs of the buildings in the area, and gives a description. Please take the time to read this information. Round buildings can have slightly different construction materials in other areas of the world, and their roofs will appear different - the project instructions will often include guides to help you understand what you are seeing.

Do your best - even the experts will disagree sometimes, and sometimes you just have to go there to see exactly what is really there. If in doubt add it as a building.

Building Tags

As we are tagging buildings we have never visited and are not familiar with, the safest and recommended tagging scheme is building=yes which you can see on a correctly tagged building if scroll to the bottom of the tagging pane and click on All tags.

See also

Ivan Gayton’s diary entry for Hadjer Lamis, Chad - comments from others indicate the description fits other parts of the world as well


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Official HOT OSM learning materials