#3126 - 2017 Sri Lanka Floods: Mapping Buildings in Matara District, Southern Province (2/2) (Archived)

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This project was archived.

Monsoon rains caused severe flooding and mudslides in western and southern Sri Lanka leaving at least 150 people dead and 500,000 people affected. Reports of the worst affected areas are to the south-western district of Kalutara with at least five mudlsides being confirmed, and resident being advised to evacuate homes. Local authorities closed schools in the Sabaragamuwa province due to heavy flooding. The Sri Lankan navy and airforce have been deployed to provide emergency relief to affected areas. The Disaster Management Centre (DMC) of Sri Lanka warned that the conditions could worsen with aid organisations remaining on high alert over the coming days.

Created by bgirardot - Updated - Priority: urgent


Changeset Comment
#hotosm-project-3126 Mapping buildings in Sri Lanka for floods in 2017 #source=DigitalGlobe premium
When saving your work, please leave the default comment but add what you actually mapped, for example "added buildings and a residential road".

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PRIORITY AREAS UPDATED - Please check instructions often - projects or priority areas may change.

Project Specific Mapping Notes

  • 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.
  • Imagery - We are using DigitalGlobe Premium imagery, which should load by default.
  • Somewhat dense mapping - Please be extra careful not to connect things, in the iD web editor, holding down the "alt" key will keep nodes of "snapping" to each other and accidentally connecting.
  • Split Tasks - After you "Start Mapping" you will see a "Split" link. If the task square is just way too much mapping for 15 to 30 mins of mapping, click on the "Split" link to make 4 smaller ones.
  • Map buildings half-in and half-out of your task square Try to pick task squares with no one mapping next to you, but always map buildings that are 25% or more in your task square.


  • 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.
  • After drawing the outline, use the 's' key in the iD 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, holding down the "alt" key will keep nodes of "snapping" to each other and accidentally connecting.
  • In the iD web editor, the first time you map a building you will use the "Building Features" category and then at the top 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.

Only 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 Notes

  • Be as precise as possible - This takes a little bit of practice, but following a road closely or the outline of a building carefully really makes a difference in the quality of map data produced. Quality is more important than quantity when it comes to mapping. Zooming in close helps.
  • changeset comments - These are filled in with some default information but you should always add what you mapped. For example "added buildings and roads" or "added in some waterways"
  • 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.
  • Personal knowledge - If you have local knowledge, that is incredibly valuable and any information you are 100% sure of you can add to the object you are mapping. Building names, health facilities, names of roads, etc, are all very valuable and the name= tag can be used to supply that information.
  • Sometimes a task square is already mapped - Sometimes you will find a task square that looks totally mapped or has nothing in it to map. Just double check that it is complete, map anything that was missed, straighten up anything that needs it and then mark it "Done".
  • 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 in not easy but know that your mapping is used by humanitarian organizations around the world every single day.

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