#1915 - Sri Lanka Floods: Eastern Kelani River Basin (Archived)

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This project was archived.

The Disaster Management Center of Sri Lanka has requested HOT's generating an estimate of the number of buildings affected by flooding in the Kelani River Basin. We'll map all the visible buildings and roads to make this possible. Please read the instructions carefully.

This task covers the eastern portion of the Kelani River Basin.

Created by Rbanick - Updated - Priority: low


Entities to Map
buildings mainly, major roads if needed
Changeset Comment
#hotosm-project-1915 #Sri-Lanka-Floods #opendri #opencities
When saving your work, please leave the default comment but add what you actually mapped, for example "added buildings and a residential road".


  • Imagery source is different from the ones used in projects 1913 and 1914. For accurate tracing of buildings please use Bing imagery. However, Mapbox imagery more precisely aligns with GPS data in this area. Either use Bing to trace features and then align them with Mapbox imagery; or align Bing imagery with features aligned to Mapbox before tracing. Mapbox imagery also has the most recent imagery source, so please make sure to add new buildings from this imagery.

  • Please watch this video to understand how to alternate between Bing and Mapbox imagery in iD editor.

Project specific guidance

  • Only add or fix major roads if needed. Be careful not to upset the existing road relationships as the OSM-LK community has invested a lot of time and effort making the road routing work successfully in GPS devices.
  • Many of these squares will already be partially or fully mapped, map in more if needed or fix up the existing mapping, or just mark it "Done" if it is already complete.


  • Please accurately outline all the buildings you can find. The outline should be for the full size of the building even if it is partly covered by trees in the imagery.
  • It is ok to "split" task squares - Sometimes a task square will have a lot detailed settlement mapping. If you think it would help to make the task square smaller so the mapping could be finished in a more reasonable time, use the "split" link above the task square comment box.
  • After drawing the outline, use the 's' key in the web editor to "square" the corners.
  • Many buildings are very close, but do not actually touch each other, try to map them close to each other without letting them connect or share nodes with each other, roads or residential area outlines.
  • In the iD web editor, the first time you map a building you will use the "Building" category and then at the bottom of the list select "Building" again, this is the most generic building tag we can use as we almost never can tell the more specific use of any building from imagery alone.
  • If you have personal knowledge of a building, please add that information to the building, like the name or type of building (hospital, school, gas station, etc)

General mapping guidance

  • Invalidated task squares - You might get a notice that a task square was "invalidated" that almost always just means someone found a few more things to map and they did not have time to map them in. No worries, it is part of the process and happens all the time. If you have to stop mapping before you have mapped everything use the "Unlock" link instead of "Done" As long as you are trying to map everything in a task square you feel confident mapping before you mark one "Done" then all is good.
  • Ask questions - if you have questions, please ask. The front page of this HOT Tasking Manager website offers a few ways to ask or if you are at a mapping event, raise your hand and ask.
  • You are making a real difference mapping - Every contribution matters in a real, tangible way. Mapping is not easy but know that your mapping is used by the Disaster Management Centre of Sri Lanka in near real time.


See Sri Lanka Tagging Guidelines for local mapping guidance.

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Contributors Done Assigned