The blow instructions are from the GIS Earth Day 2023 Mapathon. These directions only apply to project #GRMI: YOLA (NIGERIA) – MAPPING BUILDINGS TO IMPROVE FLOOD PREPAREDNESS.

As you edit, you will notice a number of edits on the top toolbar. Save your edits periodically. We ask that you use the hashtag #UDEarthDay23 when saving so we can track your contribution.

There is a guide with images on the project page. The text is also copied below.

Project Specific Mapping Notes

  • A few of these squares may already be partially mapped, please review and map missing features if needed, fix up the existing mapping, or just mark it “Done” if already completely well mapped.

Imagery Notes

  • Please use the Maxar Premium Imagery to do your mapping. (You are welcome to switch to Bing Imagery in case the Maxar Premium Imagery has some cloud cover)

Tracing Buildings Reference

  • 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.
  • Take care to not include the building shadow in the building outline.
  • Buildings may be 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 from “snapping” to each other and accidentally connecting.
  • After drawing the outline and tagging as a building, use the ‘Q’ key in the iD & JOSM editors to “square” the corners. We suggest using the Buildings plug-in in JOSM to make building tracing more efficient.
  • In the iD web editor, you will only have the option to tag new features as buildings, see below for editing or adding other features.
  • 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)

Changes Set Comments

  • Adding the following to your comments when you finishing mapping: #UDEarthDay23 Changeset comment:#hotosm-project-14513-#Flooding #IDP


  • The shortcut to create a new building is ‘3’.
  • To square a building, type ‘S’ after you select the feature as a building.

Start Making Edits to Map