1. A system for detecting elevated structures using three-dimensional point cloud data, the system comprising: one or more processors and a memory having instructions such that when the instructions are executed, the one or more processors perform operations of: receiving a set of data from a three-dimensional point cloud of a landscape, wherein the set of data points comprises inlier data points and outlier data points; identifying the inlier data points in the three-dimensional point cloud data; combining the inlier data points into a plurality of segments, wherein each segment in the plurality of segments represents a planar, horizontal or near-horizontal extent in the three-dimensional cloud data; filtering the plurality of segments to generate a plurality of filtered segments, the plurality of filtered segments having overlapping parts; converting each of the filtered segments into an image comprising one or more horizontal image levels, wherein the number of image levels depends on a maximum number of overlapping parts of the filtered segments; processing each image level with an edge detection algorithm to detect elevated edges in the filtered segments; and vectorizing the elevated edges to identify a multi-level elevated structure of interest in the landscape wherein, the multi-level elevated structure of interest is selected from the group consisting of bridges, overpasses, and ramps.