1

Fig. 1. Overview map of the logging sites from which harvester data were collected, and corresponding airborne laser scanning datasets with year of acquisition (ALS year).

Table 1. Airborne laser scanning acquisition parameters, footprint diameters and pulse densities.
Year Instrument Time period Pulse rate
(kHz) 		Scan rate
(Hz) 		Flying altitude
(m) 		Scanning angle
(±°) 		Footprint diameter
(m) 		Pulse density
(m–2)
2013 TopEye S/N 444 May–July 200 92 1500 20 0.28 7.7
2016 Riegl LMS Q-1560 September 400 100 2900 20 0.25 3.2
2017 Riegl VQ-1560 I July 700 240 2300 20 0.58 6.8
2019 Leica ALS70-HP August 495 69 1150 16 0.73 5.9
2020 Riegl VQ-1560 II June 749 158 1100 29 0.75 10.4
2

Fig. 2. The enhanced area-based inventory approach used in this study. (A) buffer around positions of harvested stems, (B) hexagonal grid, (C) overlay with polygons of tree crowns segmented from the ALS data, (D) cell borders adjusted for segmented trees and sliver cells and (E) cells within a –15 m buffer used in Monte Carlo simulations marked with dashed lines.

Table 2. Number of cells (n), selected predictors, model fit statistics for different cell sizes and accuracies of timber volume estimates for logging operations.
Cell size
(m2) 		n Predictors Pseudo R2 RMSE%w ME%w Min error
(m3 ha–1) 		Max error
(m3 ha–1) 		Mean error
(m3 ha–1)
100 10595 Hmax + Hmean + D1 0.52 14.93 –0.06 –87.6 58.9 0.3
200 5707 Hmean + D0 0.59 14.07 –0.04 –83.4 67.9 3.4
300 3929 Hmean + D0 0.63 14.30 –0.27 –88.7 64.5 2.3
400 3038 H80 + D0 0.63 12.71 –0.32 –74.7 56.9 3.1
Table 3. Logging operation level statistics for harvester data obtained from the 33 operations.
Min Mean Max Std.dev
Mean timber volume (m3 ha–1) 115 248 419 84
Mean diameter at breast height (mm) 157 209 277 29
Number of stems 4442 149 629 518 012 125 542
Harvested area (ha) 0.14 3.03 10.21 2.64
3

Fig. 3. Observed timber volume plotted against timber volume estimated from airborne laser scanner (ALS) data acquired from 2013 to 2020 (ALSyear) for the 33 logging operations and four cell sizes.

4

Fig. 4. Mean values of RMSE% of cell level timber volume predictions obtained for the four cell sizes and simulated positioning errors of harvested stems.

5

Fig. 5. Mean values of RMSE%w of timber volume estimates at logging operation level obtained for the four cell sizes and simulated positioning errors of harvested stems.