World Forestry

The Silviculture and Forest Models (SFM) Team has been cooperating with the Precision Forestry Cooperative (PFC) located at the University of Washington to evaluate the accuracy of LIDAR (LIght Detection And Ranging) and IFSAR (interferometric synthetic aperture radar) data for terrain and vegetation structure measurements.

LIDAR is a remote sensing technology that bounces laser pulses off the vegetation and ground as a data collection aircraft flies across a landscape (figure 1). The LIDAR system converts the reflected laser pulse data into a cloud of high-resolution three-dimensional coordinates (figure 2) that can then be used to measure both the ground surface and vegetation structure on a landscape (figure 3).

Figure 2: LIDAR data cloud for a section of Capitol State Forest, Blue Ridge Site.

IFSAR is another remote sensing technology; it uses radar, rather than laser light, to measure vegetation and terrain. The team is developing LIDAR and IFSAR measurement tools to collect vegetation characteristics such as tree density, tree size, canopy cover, canopy volume, and crown bulk density over landscapes at high spatial resolution (1 m to 3 m).

Our research efforts to date include:

• accuracy assessments of LIDAR-derived terrain models using ground surveyed control points,
• development of algorithms to locate individual trees and characterize their size and overall crown shape using raw LIDAR returns,
• comparison of LIDAR-derived terrain and canopy models with photogrammetric measurements collected from 1:3,000 color photography, and
• the comparison of terrain and canopy surface models derived from LIDAR data with models developed using IFSAR data.

Figure 3: Canopy and terrain surface models, Blue Ridge site

Fonte: USDA Forest Service