Software and Data Use the skyline fans to slice vertical sticks within the area of interest. The virtual lines indicate elevations that cannot be seen from the road. The top vertex of each is displayed as a point feature. by converting the infinitely thin flight paths into volumetric flight corridors. One simple way to do this is to buffer the flight path into a polygon and extrude that polygon between a minimum and maximum altitude range. Using the volume-based Intersect 3D geoprocessing tool (rather than the line-based Intersection tool), all the threat volumes within the corridor can be derived. This provides additional options for accessing flight safety. For example, the north side of a flight corridor could be safer than the south. It also provides a more complete summary of the total dangers associated with a flight corridor. www.esri.com Note: The 3D volumetric analysis tools can create incredibly complex geometries that can contain hundreds of thousands of triangles, which may exceed the number of operations that can be run. However, this restraint is expected to ease over time as the underlying Computational Geometry Algorithms Library (CGAL) expands. Example 2: Hiding Tall Buildings The second question we'll examine, How tall can these buildings be without being visible from nearby major roads? is a real urban development use case that has been mandated by law in many countries. However, the same workflow could also be applied to other scenarios: placing mining rigs so they can't be seen, finding locations that hide military vehicles from view, or identifying sections of a forest that can be harvested while minimally impacting the appearance of the surrounding countryside. This scenario is similar to the children's game of hide-and-seek—find a place where it's hard for others to see you. This seemingly simple problem can be challenging to solve using software. However, by thinking creatively, 3D analysis tools can be used to figure out where Continued on page 12 ArcUser Fall 2010 11