Buildings

Now check if buildings are missing. If there are a large number missing, the grid can be invalidated. If it's only a few then it's simpler to add them as you check around.

Are the buildings correctly traced? Sometimes mappers do not trace buildings accurately & if you spot significant inaccuracies this needs correcting. You may find that a group of buildings looks like they match the shape of roofs but are displaced from where the building is in the imagery, this often happens when OSM has been traced based on imagery that has been misaligned. For the purposes of this task - unless the alignment is aggregious - leave the buildings if you suspect displacement is due to an imagery issue.