MODELING LIDAR WAVEFORMS USING A RADIATIVE TRANSFER MODEL

In the past, obtaining reliable measurements of key forest canopy metrics has been difficult, even after the development of remote sensing technology. Fortunately, next-generation lidar systems are proving to be useful tools for deriving critical canopy measurements, such as height, structure and biomass. These studies have all focused on empirical comparisons between basic lidar-derived and field-sampled measurements. The results of these studies have shown that lidar remote sensing instruments can successfully measure forest canopy characteristics. However, physically-based remote sensing models are necessary to more fully understand and interpret the interactions of the laser energy with the forest canopy. In this study the Geometric Optical and Radiative Transfer (GORT) model is used to model lidar waveforms. GORT is capable of modeling lidar returns from canopies with clumped multiple layers and multiple species. For this study, GORT was used to model waveforms over the Sierra National Forest in California. Field data input into GORT are a representative sample of the different vegetation types found in the forest. The modeled waveforms are then validated against actual lidar data collected by the Laser Vegetation Imaging Sensor (LVIS) which mapped the area in October 1999. By modeling lidar waveforms based on the physical principles of radiative transfer, GORT fills a missing link between the remotely sensed and actual canopy structure. The results of this study will also aid in future large-scale land surface mapping by developing a link between lidar and other remote sensing data.

[1]  D. B. Coyle,et al.  Optimization of an airborne laser altimeter for remote sensing of vegetation and tree canopies , 1994, Proceedings of IGARSS '94 - 1994 IEEE International Geoscience and Remote Sensing Symposium.

[2]  R. Dubayah,et al.  Estimation of tropical forest structural characteristics using large-footprint lidar , 2002 .

[3]  David R. Miller,et al.  Vertical Overstory Canopy Architecture of Temperate Deciduous Hardwood Forests in the Eastern United States , 1999 .

[4]  Alan H. Strahler,et al.  A hybrid geometric optical-radiative transfer approach for modeling albedo and directional reflectance of discontinuous canopies , 1995, IEEE Transactions on Geoscience and Remote Sensing.

[5]  Paul J. Curran,et al.  Factors affecting the remotely sensed response of coniferous forest plantations , 1993 .

[6]  D. Harding,et al.  REMOTE SENSING OF FOREST CANOPIES , 1996 .

[7]  Geoffrey G. Parker,et al.  Access to the Upper Forest Canopy with a Large Tower Crane , 1992 .

[8]  M. North,et al.  Analyzing canopy structure in Pacific Northwest old-growth forests with a stand-scale crown model , 1996 .

[9]  Wenge Ni-Meister,et al.  Modeling lidar waveforms in heterogeneous and discrete canopies , 2001, IEEE Trans. Geosci. Remote. Sens..

[10]  J. Blair,et al.  The Laser Vegetation Imaging Sensor: a medium-altitude, digitisation-only, airborne laser altimeter for mapping vegetation and topography , 1999 .

[11]  J. Hyyppä,et al.  Accuracy comparison of various remote sensing data sources in the retrieval of forest stand attributes , 2000 .

[12]  W. Cohen,et al.  Surface lidar remote sensing of basal area and biomass in deciduous forests of eastern Maryland, USA , 1999 .

[13]  J. Means.  Use of Large-Footprint Scanning Airborne Lidar To Estimate Forest Stand Characteristics in the Western Cascades of Oregon , 1999 .