1. A system for construction estimation, comprising: a computer system for receiving at least one aerial image of a building; and an estimation engine in said computer system for processing the aerial image to estimate one or more features relating to a roof of the building, the estimation engine: processing the aerial image with a filter to compute a likelihood for each point in the aerial image indicating whether the point represents a roof line; scanning the aerial image at a first angle to obtain first image intensity data; rotating the aerial image to a second angle different from the first angle; scanning the aerial image at the second angle to obtain second image intensity data; processing the first and second image intensity data to automatically identify a plurality of lines in the aerial image corresponding to one or more features of the roof; constructing a two-dimensional model of the roof using the plurality of lines identified in the aerial image; and manipulating the two-dimensional model into a three-dimensional model of the roof by displaying the two-dimensional model superimposed onto an oblique image of the roof and allowing the user to click and drag perimeter and interior points of the two-dimensional model to corresponding points on the oblique image of the roof.