Derivation of Effective Aerodynamic Surface Roughness in Urban Areas from Airborne Lidar Terrain Data

Abstract

An automated technique was developed that uses only airborne lidar terrain data to derive the necessary parameters for calculation of effective aerodynamic surface roughness in urban areas. The technique provides parameters for geometric models that have been used over the past 40+ years by automatically deriving the relevant geometry, orientation, and spacing of buildings and trees. In its prototypical form, this technique subsequently calculates an effective surface roughness for 1-km2 parcels of land for each of five geometric models. The user can define several constraints to guide processing based on a priori knowledge of the urban area or lidar data characteristics. Any given wind direction (or range of directions) can be selected to simulate conditions of variable wind flow and the impact on effective surface roughness. The operation, capabilities, and limitations of the technique were demonstrated using lidar terrain data from Broward County, Florida.