In an embodiment, a method for identifying building unit rooftops, and their associated heights and locations is provided. The method includes subtracting a bare earth layer from a first return layer within a LIDAR data set for a geographic area of interest to form an above ground level (AGL) layer data set. A height mask is then applied to the AGL layer data set to form a building units data set. The building units data set includes data representative of potential building unit rooftops. This data set is refined through the application of a series of filters and masks to remove clutter (e.g., trees, bushes and other non-building unit structures) to refine the data set.