Table 1. Specifications of Leica HDS6100 terrestrial laser scanner (Leica Geosystems AG).
Wavelength 650–690 nm
Field-of-view 360° × 310°
Max. point spacing 1.6×1.6 mm at 10 m, 4.0×4.0 mm at 25 m
Point spacing in this experiment 6.3×6.3 mm at 10 m, 15.9×15.9 mm at 25 m
Max. acquisition rate 508 000 points / second
Laser beam diameter at exit 3 mm
Laser beam divergence 0.22 mrad
Laser spot size at 25 m 8 mm
Method of distance measurement Continuous wave, Frequency modulation
Precision of distance measurement 0–25 m: < 3 mm, 25–50 m: < 5 mm
Precision of angular measurement H: 7.9 mgon, V: 7.9 mgon
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Fig. 1. Tree height estimation with field measurements (VertexH) and TLS derived data (CylH).

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Fig. 2. Cylinder volume distributions (describing the branch volume) for all trees in the tree height class of 22–24 m. The total volume in y-axis refers to the sum volume of all cylinders of the diameter shown in the X-axis.

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Fig. 3. Top: average cylinder volume distribution functions for all tree height classes. Lower: the cylinder volume distributions for all tree height classes, normalized to 1 at the largest cylinder diameter (3 cm). The normalization enabled us to compare the shapes of the volume distributions.

Table 2. Detailed statistics of all 4 tree height classes.
Tree height (VertexH) < 20 m 20–22 m 22–24 m > 24 m
Number of trees 5 12 14 10
Mean total branch volume 0.31 m3 0.561 m3 0.591 m3 0.514 m3
Standard deviation 0.070 m3 0.104 m3 0.046 m3 0.044 m3
Skew 1.661 1.931 2.39 1.88
Tree height (TLS) 16.1–18.9 m 20.3–21.8 m 22.1–23.3 m –25.1 m
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Fig. 4. Left: intensity image shows moving branches during the scan. Right: close-up of a worst-case QSM model reveals gaps and false cylinders in the canopy.