1

 Fig. 1. Location of the test area.

Table 1. Average, maximum (Max) and standard deviation (Std) of field variables in the field data sets (for all variables: minimum = 0).
  2011 plots (81) 2012 plots (165)
Forest variable Average Max Std Average Max Std
Total volume, m3/ha 215.8 529.4 110.9 213.6 653.6 119.2
Volume of Scots pine, m3/ha 76.0 314.3 80.4 77.9 314.3 80.8
Volume of Norway spruce, m3/ha 97.2 448.9 118.9 88.3 561.3 114.2
Volume of broadleaved, m3/ha 42.7 249.9 51.6 47.4 403.4 66.9
Mean diameter, cm 23.5 56.2 9.9 24.1 59.1 8.8
Mean height, m 20.2 34.7 7 20.6 34.7 6.3
Basal area, m2/ha 22.5 46.7 9.3 22.1 56.8 9.4
2

Fig. 2. The volume distribution of the dataset plots used with 2011 and 2012 image acquisition.

Table 2. Camera sensors fitted to UAVs.
Camera Ricoh GR Digital III Olympus E-420
Sensor type CCD CMOS
Image sensor size 17.3 mm ×13.0 mm 17.3 mm × 13.0 mm
Image resolution 3648 × 2736 pixels 3648 × 2736 pixels
Field of View (FOV) 65° × 51° 38.1° × 29.1°
Pixel size 4.74 µm 4.74 µm
Groud sample distance* 5.2 cm 8.5 cm
Spectral bands** 490 – 600 nm
600 – 700 nm
700 – 1000 nm 		490 – 600 nm
600 – 700 nm
700 – 1000 nm
Frame rate 0.25 Hz 0.5 Hz
Weight 220 g 380 g
Size 109 × 60 × 26 mm 129.5 × 91 × 53 mm
*At the applied flying altitude **Both Ricoh and Olympus had a blue cutting filter Schott GG495 which has a cut-off wavelength 495 nm.
3a

Fig. 3a. UAV flight lines of the 2012 photo acquisition. The take-off and landing site is located approximately 300 m north-east of Ylinen Rautjärvi (approach and descent curves made by the UAV prior to landing can be seen on the map).

3b

Fig. 3b. Location of field plots of 2011 (green) and 2012 (red).

Table 3. UAV systems (Trimble unmanned aircraft systems 2013, Bramor UAS family 2013).
UAV Gatewing X100 C-Astral Bramor
Wing span (cm) 100 230
Fuselage length (cm) 60 96
Take-off weight (kg) 2.2 4.2
Payload compact camera 0.6 – 1.0 kg
Propulsion type electric electric
Take-off/landing catapult launch/belly landing catapult launch/parachute landing
Flight endurance (min) 45 120
Altitude ceiling (m) 2500 5000
Table 4. The feature combinations selected by GA for estimating forest variables based on data of 20 and 50 cm spatial resolutions (DBH = diameter at breast height, v. = volume of growing stock, for feature abbreviations see section 2.4).
Height (20 cm) STD_G, H05, H30, H80, H85, H95, HCV, VEG, P60, IDM_R, MOC_G, MOC_H, SV_H
Height (50 cm) STD_G, HAVG, H30, H40, H85, H95, H100, P40, DV_R, MOC_G, MOC_H, SV_H
DBH (20 cm) HSTD, H0, H90, H95, H100, P20, P60, MOC_NIR, ASM_R, ENT_G, DE_H, MOC_H
DBH (50 cm) H30, H90, H100, P60, P95, SA_G, COR_H, MOC_H, SA_H
Basal area (20 cm) HAVG, H20, H40, H80, H90, D3, ENT_NIR, SV_R, ASM_G, ASM_H, CON_H
Basal area (50 cm) HSTD, H20, H40, H70, H80, D2, P40, DE_NIR, SV_R, CON_H, DE_H, MOC_H
V. total (20 cm) HSTD, H10, H70, H80, H85, H90, H95, D0, P60, SA_R, CON_H, DV_H
V. total (50 cm) HAVG, HSTD, H20, H30, H90, P20, DE_NIR, SA_R, ASM_H, CON_H
V. pine (20 cm) MEAN_NIR, H20, H80, H85, H95, D2, D6, D9, P60, COR_NIR, DE_NIR, IDM_H, SV_H
V. pine (50 cm) STD_G, H20, H40, H80, H85, H95, HCV, VEG, P80, PCG, DV_NIR, SE_R, CON_G, DV_G, SE_G, IDM_H, MOC_H
V. spruce (20 cm) MEAN_NIR, HSTD, H40, H70, H100, D3, P80, IDM_H
V. spruce (50 cm) MEAN_NIR, STD_G, HSTD, H20, H050, H80, H95, HCV, D3, ASM_R, IDM_R, ASM_G, DE_G, CON_H, IDM_H, MOC_H
V. broadleaf (20 cm) HSTD, H0, H40, H80, H90, D2, D8, PGH, SV_NIR, COR_G, ASM_H, IDM_H, SA_H, VAR_H
V. broadleaf (50 cm) STD_R, H050, H85, H100, D8, P95, ASM_NIR, ASM_R, COR_R, SA_R, MOC_G, CON_H, COR_H, MOC_H, VAR_H
4

Fig. 4. Relative RMSE values [%] for estimated forest variables at sample plot level (2011 data, orthoimage resolutions 20 and 50 cm). Variables: v = volume, g = basal area, hgm/dgm = mean height/diameter (as measured from basal-area weighted median tree).

5

Fig. 5. Relative RMSE values [%] for estimated forest variables at sample plot level (2011 and 2012 data, orthoimage resolution 50 cm).