The comparison between the predictions of LiDAR and the observations in the field (354 trees) confirmed that the ALS underpredicted individual tree heights by 7 to 8%. The analysis of the residuals did not show any bias in the data and the relationship proved to be fairly consistent for all the tree diameter ranges. The tree height recovery model created from the linear relationship was able to predict 73% of all the heights within 1 m; 91% within 1.5 m and 96% within 2 m. The analysis of the results proved consistent in all the diameter distributions (Table 1). The largest variations were obtained in diameters between 20 and 30 cm due to the low number of trees in this diameter range and the existence of a few outliers. In the smallest diameters, the relationship between predictions and observations seem to suggest that LiDAR can predict tree tops more efficiently that in the case of the larger trees. A possible explanation could be the small number of observations in this range. Another explanation related to the fact that these trees are generally sub-dominants. That means they have canopy heights below the mean height of the surrounding trees. As they tend to grow near the bigger trees our method of classification seems to misinterpret the information retrieve for these trees
Finally, our method of classification did not seem to map canopy dimensions at individual tree level. The segmentation method created a group of polygons that represented each individual tree. Nevertheless, the subsequent classification was not able to discriminate individual each canopy dimensions in a 2-D plane. Therefore, more work should be done in order to estimate diameter distributions and volume from current models that link canopy architecture with diameter classes