## 3 Methods
### Stand Data Based on Forest Plots  
Altogether 426 grid cells measuring 32 m by 32 m were created alongside the trajectory, with the center points of the cells following the trajectory. The forest inventory attributes for the grid cells were predicted using the ALS data (acquisition date 5 September 2014, point density 6 points per m\({}^{2}\)), the field measurements of the sample plots with the respective size in the same area (\(n\) = 90), and an algorithm created at the FGI [38; 39; 40]. First, the point clouds from sample plot areas and grid cells were extracted from the ALS data and used to calculate the statistical parameters. The parameters were calculated from normalized ALS data above the threshold value of 2 m, _i.e._, the points higher than 2 m above ground, and the parameters included minimum height, maximum height, mean height calculated as the arithmetic mean of laser-based heights, standard deviation of the heights, coefficient of variation, penetration, percentiles calculated from 10% to 90% of canopy height distribution at 10% intervals, and canopy cover percentiles expressed as the proportion of returns below a given percentage of total height from 10% to 90% of the heights. With all this done, the prediction model was developed based on these features and field-measured forest inventory attributes from 90 sample plots using random forest technique, which is a non-parametric regression technique. Finally, the forest inventory parameters for 426 grid cells were estimated based on the developed model and the ALS features derived for the areas. The predicted forest inventory parameters were mean tree height, mean DBH, basal area, volume, and biomass, in addition to the ALS penetration rate. The RMSE-% values achieved were 5.2% for mean tree height, 11.9% for mean DBH, 15.4% for basal area, 18.4% for volume, and 15.3% for biomass.  
The stands were classified into four categories based on the mean tree height: young pine stand (\(<\)21 m), young spruce stand (21-25 m), mature pine stand (25-27.5 m), and mature spruce stand (\(>\)27.5 m). The general data on the stands is shown in Table 6.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Stand Type**} & **Mean Tree** & **Mean** & **Basal Area** & **Volume** & **Biomass** & **Penetration** \\  & **Height (m)** & **DBH (cm)** & **(m\({}^{2}\)/ha)** & **(m\({}^{3}\)/ha)** & **(Mg/ha)** & **Rate (\%)** \\ \hline Young pine & 19.4 & 19.0 & 22.2 & 218.1 & 108.0 & 45.5 \\ Young spruce & 23.9 & 18.6 & 31.5 & 352.1 & 162.1 & 32.7 \\ Mature pine & 26.3 & 20.4 & 34.3 & 411.0 & 180.6 & 30.1 \\ Mature spruce & 28.7 & 22.2 & 37.3 & 447.4 & 197.1 & 26.0 \\ \hline \hline \end{tabular}
\end{table}
Table 6: General data on the stands.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Device** & **Type** & **Antenna** \\ \hline Garmin eTrex 30 & Handheld single-frequency navigator & In-built \\ u-blox MAX-M5Q & Single-frequency receiver & External generic patch \\ NVS NV08C-CSM & Single-frequency receiver & Maxtena M1227 HCT-A-SMA \\ NovAtel FlexPak6 & Dual-frequency geodetic receiver & NovAtel GPS-702-GG \\ \hline \hline \end{tabular}
\end{table}
Table 5: The tested GNSS devices.