Common use of LIDAR Method Clause in Contracts

LIDAR Method. Canopy percent cover suitable for LiDAR assessment was not measured by the field crew as the cost and time to collect such data were deemed to be prohibitive. Moreover, canopy percent cover from LiDAR has already been established as a metric that is strongly related with LiDAR data in the literature, as documented in our previous pilot literature review (Xxxxxx & Xxxxx 2015). Hemispherical photos were taken from plot center, but these photos were not processed to estimate cover. Although denisometer data was collected in the field the collection of such data is user subjective, and does not capture the structural three dimensional component of the canopy, thus, it is rarely used for comparisons to such high precision, three dimensional data as LiDAR. The densitometer is more suitable to understanding canopy closure. LIDAR can be processed to estimate canopy percent cover. The Fusion program CloudMetrics (XxXxxxxxx, 2016) calculates several different cover metrics, all of which are different ratios of crown to non-crown LIDAR returns. The theory behind these metrics is that the denser the canopy, the less the laser will penetrate below the canopy, resulting in fewer non-crown returns. The available cover metrics from CloudMetrics are:  Percentage of first returns above a specified height  Percentage of first returns above the mean height  Percentage of first returns above the mode height  Percentage of all returns above a specified height  Percentage of all returns above the mean height  Percentage of all returns above the mode height  Number of returns above a specified height / total first returns * 100  Number of returns above the mean height / total first returns * 100  Number of returns above the mode height / total first returns * 100 Typically, we consider the first metric, Percentage of first returns above a specified height, to be canopy percent cover. For this project, that was Percentage of first returns above two meters (6.56 ft.). First returns are more likely reflect off of the canopy than subsequent returns. Therefore, locations where first returns are reflecting off of objects below the two-meter height threshold likely have open canopy. The two-meter height threshold was chosen to separate trees from shorter shrubs.

LIDAR Method. Canopy percent cover suitable for LiDAR assessment was not measured by the field crew as the cost and time to collect such data were deemed to be prohibitive. Moreover, canopy percent cover from LiDAR has already been established as a metric that is strongly related with LiDAR data in the literature, as documented in our previous pilot literature review (Xxxxxx & Xxxxx 2015). Hemispherical photos were taken from plot center, but these photos were not processed to estimate cover. Although denisometer data was collected in the field the collection of such data is user subjective, and does not capture the structural three dimensional component of the canopy, thus, it is rarely used for comparisons to such high precision, three dimensional data as LiDAR. The densitometer is more suitable to understanding canopy closure. LIDAR can be processed to estimate canopy percent cover. The Fusion program CloudMetrics (XxXxxxxxx, 2016) calculates several different cover metrics, all of which are different ratios of crown to non-crown LIDAR returns. The theory behind these metrics is that the denser the canopy, the less the laser will penetrate below the canopy, resulting in fewer non-crown returns. The available cover metrics from CloudMetrics are:  • Percentage of first returns above a specified height  • Percentage of first returns above the mean height  • Percentage of first returns above the mode height  • Percentage of all returns above a specified height  • Percentage of all returns above the mean height  • Percentage of all returns above the mode height  • Number of returns above a specified height / total first returns * 100  • Number of returns above the mean height / total first returns * 100  • Number of returns above the mode height / total first returns * 100 Typically, we consider the first metric, Percentage of first returns above a specified height, to be canopy percent cover. For this project, that was Percentage of first returns above two meters (6.56 ft.). First returns are more likely reflect off of the canopy than subsequent returns. Therefore, locations where first returns are reflecting off of objects below the two-meter height threshold likely have open canopy. The two-meter height threshold was chosen to separate trees from shorter shrubs.