Sagebrush Canopy Height and Shape Measurements Using Small-Footprint Discrete-Return LiDAR
The objective is to fi nalize and publish shrub height and shape prediction errors results obtained by comparing LiDAR point-cloud data to sagebrush canopy characteristics measured in the field.
From May to October 2009, height and shrub measurements were collected for 107 individual sagebrush, and bare earth elevations were collected throughout 11 circular plots 20 m in diameter. The sagebrush ground reference data were used to evaluate high density (average density of 9.46 points/m2), small-footprint, discrete-return LiDAR data collected over portions of the INL Site on December 13, 2006.
The results demonstrated that the LiDAR-derived sagebrush height estimates were significantly and strongly correlated with corresponding field-based height estimates, with observed coefficients of determination of 0.84 – 0.86. Similarly, LiDAR predictions of shrub shape and area were significantly and strongly correlated, with field-based measurements resulting in coefficients of determination of 0.65 – 0.78. Although LiDAR tended to underestimate shrub area, this study provided the first shape and area estimates for LiDAR-based measurements of low-height vegetation (i.e., shrubs). Error in height estimates are thought to be associated with greater canopy penetration by the LiDAR signal and error in area estimates are likely associated with failure to properly delineate individual shrubs in the LiDAR data.