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, m^{3}/ha | 215.8 | 529.4 | 110.9 | 213.6 | 653.6 | 119.2 |

Volume of Scots pine, m^{3}/ha | 76.0 | 314.3 | 80.4 | 77.9 | 314.3 | 80.8 |

Volume of Norway spruce, m^{3}/ha | 97.2 | 448.9 | 118.9 | 88.3 | 561.3 | 114.2 |

Volume of broadleaved, m^{3}/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, m^{2}/ha | 22.5 | 46.7 | 9.3 | 22.1 | 56.8 | 9.4 |

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. |

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 |