Building footprints mapping using 10cm LiDAR data

Building footprints are those roof portions which are exclusive of garages or sheds. The building footprint product offers polygons showing only the building outline. Building footprints along with height attribute are decisive for flood inundation modelling.

Traditionally roofs were mapped either through aerial photo interpretation or through the deployment of semi-automated feature extraction routines. To precisely map them we need orthophotos of a good vertical accuracy. Procurement of true orthophoto product is often expensive. To map only building footprints, arduous and expensive manual photo interpretation has been only the workable choice.

Melbourne Water has recently procured a 10cm LiDAR product covering most of its jurisdiction with the key intension of having a 1m ground digital elevation model. This product also comes with the non-ground point cloud. The average point separation of the product is 0.8 m. In this project, a rule-based approach has been developed to map building footprints using the 10cm LiDAR product. The rule-based approach developed made use of slope of the roof to identify flat roofs. Flat roof garages and sheds were then identified using percentage area with respect to a parcel and they were eliminated. Manual verification was carried out to finalise the building footprints and average height for footprint was extracted and stored. The results made rapid mapping of building footprints possible with the better horizontal and vertical accuracies than of aerial photos for an area of 410,800 ha.