2009

Determining Surface Roughness in Urban Areas Using Lidar Data

An automatic derivation of relevant parameters estimates surface roughness.

An automated procedure has been developed to derive relevant factors, which can increase the ability to produce objective, repeatable methods for determining aerodynamic surface roughness. Aerodynamic surface roughness is used for many applications, like atmospheric dispersive models and wind-damage models. For this technique, existing lidar data was used that was originally collected for terrain analysis, and demonstrated that surface roughness values can be automatically derived, and then subsequently utilized in disaster-management and homeland-security models.

altThe developed lidar-processing algorithm effectively distinguishes buildings from trees and characterizes their size, density, orientation, and spacing (see figure); all of these variables are parameters that are required to calculate the estimated surface roughness for a specified area. By using this algorithm, aerodynamic surface roughness values in urban areas can then be extracted automatically. The user can also adjust the algorithm for local conditions and lidar characteristics, like summer/winter vegetation and dense/sparse lidar point spacing. Additionally, the user can also survey variations in surface roughness that occurs due to wind direction; for example, during a hurricane, when wind direction can change dramatically, this variable can be extremely significant.

In its current state, the algorithm calculates an estimated surface roughness for a square kilometer area; techniques using the lidar data to calculate the surface roughness for a “point,” whereby only roughness elements that are upstream from the point of interest are used and the wind direction is a vital concern, are being investigated. This technological advancement will improve the reliability and accuracy of models that use and incorporate surface roughness.

This work was done by Donald Holland of Science Systems and Applications, Inc., for Stennis Space Center.

Inquiries concerning this technology should be addressed to the Intellectual Property Manager, Stennis Space Center, 228-688- 1929. Refer to SSC-00296-1, volume and number of this NASA Tech Briefs issue, and the page number.

White Papers

Force and Torque Measurement Traceability
Sponsored by Morehouse
Measurement of Harmonics using Spectrum Analyzers
Sponsored by Rohde and Schwarz A and D
Vision library or vision-specific IDE: Which is right for you?
Sponsored by Matrox
Improving Fidelity of Noise Repetitive Signals with Signal Averaging Technology
Sponsored by Adlink Technology
Next-Generation, Miniature High Voltage Power Modules
Sponsored by EMCO High Voltage
How To Guide for the Most Common Measurements
Sponsored by National Instruments

White Papers Sponsored By: