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 |

Fig. 1. Tree height estimation with field measurements (VertexH) and TLS derived data (CylH).

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.

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 m^{3} | 0.561 m^{3} | 0.591 m^{3} | 0.514 m^{3} |

Standard deviation | 0.070 m^{3} | 0.104 m^{3} | 0.046 m^{3} | 0.044 m^{3} |

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 |

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.