Table 1. Quantified obstacle properties, sourced from literature, and obstacle characteristics based on Campbell and Wynne’s (2011) classification of objects. If the obstacle possesses the stated characteristic, a Y (Yes) is marked. An N (No) marks if the obstacle does not possess such characteristic.
Characteristic Stone Stump Root Slash Soil
Density [kg·m–3] 2500–3200a 440–670b 301–499c 844–883d 1400–2050e
Tensile modulus [109 Pa] 40–68f 8.1–16.2b 8.1–16.2b 8.1–16.2b 4.8∙10–4–0.2g
Thermal conductivity
[W·m–1·K–1] 		2.51–3.97f 0.12–0.22f 0.12–0.22f 0.12–0.22f 0.17–2.2f
Reflectance [%]
(λ∈[300m–9 2500m–9])* 		5–80h 10–65i - 3–85i, k 0–55h, i
Moisture content
[fresh weight %] 		~0 15–64d, j 15–55j 29–56d, l 0–100
Distinguishable tone m Y Y N Y Y
Distinguishable texture
(roughness) m 		Y Y Y Y Y
Casts a shadow m Y/N Y N Y/N N
Forms a distinguishable pattern m N Y/N N N N
Other objects or features is associated to the obstacle m Y Y Y Y Y
Distinguishable shape m Y Y Y Y N
Is found on specific topological sites m N Y/N Y N N
Can be moved with force exerted during mounding or disc trenching Y/N N** Y/N Y Y
Degradation over a forest rotational period N Y Y Y N
Exists above ground Y Y Y/N Y N
Exists below ground Y N Y N Y
a Elming (1980); b Tsoumis (1991), Doran (1992), Nordling and Österman (2006); c Kalliokoski (2008); d Kärkkäinen (1976); e Parasnis (1971), Parasnis and Dattatrai (1997), Cardarelli (2008); f Saarman (1992), Cardarelli (2008); g U.S. Army… (1990); h Bowker et al. (1985); i Lang et al. (2002); j Laurila and Lauhanen (2010); k Williams (1991); l Nurmi (1999); m Campbell and Wynne (2011) * λ = wavelength of radiated light ** Applies for stumps > 100 mm in diameter
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Fig. 1. Flowchart of the activities conducted by a computer-aided system using object identification for avoidance or targeting purposes.