Building rooftop outlines for all significant structures in the City, represented by polygons. Areas for ancillary structures such as decks are not represented. The polygons are intended to be used as base data, and to represent the approximate generalised outline of the building. Note that the roofline may not match the footprint on the ground. Polygons were initially created based on aerial photgraphy from 2000, and have since been maintained based on more recent aerial orthophotography from multiple years (particularly 2012 and 2009). Updated polygons (edited in 2013/2014) have been digitised at a scale of 1:250. Updated polygons are much improved, and should have square corners (unless that wouldn't reflect reality). Other sources such as building cad drawings have been used where available. Updates will continue until all polygons have been reviewed, and will then be maintained as new orthophotography is received, and as permits are issued (particularly demolition permits).