A mixed pixel- and region-based approach for using airborne laser scanning data for individual tree crown delineation inPinus radiataD. Don plantations

Abstract

The aim of this study was to evaluate the use of high-resolution airborne laser scanner (ALS) data to detect and measure individual trees. We developed and tested a new mixed pixel-and region-based algorithm (using Definiens Developer 7.0) for locating individual tree positions and estimating their total heights. We computed a canopy height model (CHM) of pixel size 0.25 m from dense first-pulse point data (8 pulses m −2 ) acquired with a small-footprint discrete-return lidar sensor. We validated the results of individual tree segmentation with accurate field measurements made in 37 plots of Monterey pine (Pinus radiata D. Don) distributed over an area of 36 km 2 . Fieldwork consisted of labelling all of the trees in each plot and measuring their height and position, for posterior integration of the data from both sources (field and lidar). The proposed algorithm correctly detected and linked 59.8% of the trees in the 37 sample plots. We also manually located the trees by using FUSION software to visualize the raw lidar data cloud. However, because the latter method is extremely time-consuming, we only considered 10 randomly selected plots. Manual location correctly detected and linked 71.9% of the trees (in this subsample the algorithm correctly detected and measured 63.5% of the trees). The R 2 values for the linear model relating field-and lidar-measured heights of the linked trees located manually and with the automatic location algorithm were 0.90 and 0.88, respectively.

A Region-Based Hierarchical Cross-Section Analysis for Individual Tree Crown Delineation Using ALS Data

“…Additionally, the topographic effect is another factor that influenced the accuracy of the ITCD method [6,66]. Since the RHCSA algorithm detection and delineation of individual tree crowns relied on the "peak" and "valley" structures shown on CHM, it could result in errors if the structure changed due to extreme topographic factors (e.g., steep slope).…”

“…Parameters of individual trees, such as tree location, tree species, tree height, diameter at breast height (DBH), and crown diameter, are vital for sustainable and precise forest management [4][5][6]. These individual tree-related properties can also be utilized to estimate forest parameters at stand level, such as tree species composition, mean tree height, timber volume, canopy density, and mean basal area [7][8][9][10].…”

Using low density LiDAR data to map Mediterranean forest characteristics by means of an area-based approach and height threshold analysis

“…In the former approach, single-tree attributes are estimated by crown delineation, height measurement and detection of individual apexes. However, the performance of this approach is relatively poor in complex stands where individual tree segmentation algorithms frequently generate commission/ omission errors during analysis of individual trees (González-Ferreiro et al, 2013). This approach is also very expensive as it requires spatially dense LiDAR data.…”

Impact of plot size and model selection on forest biomass estimation using airborne LiDAR: A case study of pine plantations in southern Spain

“…In addition, LiDAR systems reduce groundbased measures such as tree diameters, heights and canopy parameters providing better data processing and positional accuracy than photogrammetric techniques (Maltamo et al 2004;Naesset 2004;González-Ferreiro et al 2013). It may be possible to reduce the edge effect associated with LiDAR metrics related to trees located just outside plot boundaries by considering the use of different plot sizes as part of the design parameters in forest surveys.…”

“…airborne LiDAR), and it has been accepted that a modified sampling design with adequate statistical approach is required (Zhao, Popescu 2009). Along with sampling effort, field plot shape and size selection are still among the main challenges of forest inventory design, because it is necessary to minimize potential edge effects and to capture an adequate amount of structural variability in the field (Zenner 2005;González-Ferreiro et al 2013).…”