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Stefan Tretter

LWF

Bavarian State Institute of Forestry
Section Silviculture and Mountain Forests
Hans-Carl-von-Carlowitz-Pl. 1
D-85354 Freising

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Article

Author(s): Editorial office waldwissen.net - LWF
Editorial office: LWF, Germany
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Laser scanning trees

Laserscanner
Fig. 1: A laser scanner in a South African Pinus radiata plantation. The laser scanner delivers a less than spectacular picture. However, the pictures it creates of forest stands could lead to sweeping changes in the "landscape" of forest inventory (Picture: A. Kunneke).

Laser scanning is a remote sensing method that has found its way into forestry. The practice of scanning the surface of the earth from aircraft (ALS) for use in forest inventories is utilized by many countries. Terrestrial laser scanning (TLS) is also an up and coming method.

TLS is fundamentally different from aerial laser scanning. With TLS, the laser scanner is temporarily placed in the forest and scans, in extremely high detail, the surrounding area with a very high ray density. In comparison to ALS, stem form and branchiness can be measured.

In the past several years much work has been invested in the development of this measuring technology. A method for the automatic determination of branchiness from terrestrial laser scanning has been envisaged. Here, whorl height on the stem and the number of branches per whorl can be automatically determined quite extensively. Potential gains from harvests can be calculated with these parameters and the dimensions of the stem. They also give insight about the most economically advantageous point in time to harvest.

A whorl is an arrangement of sepals, petals, leaves, stipules or branches that radiate from a single point and surroundor wrap around the stem. A whorl consists of at least three elements; a pair of opposite leaves is not called a whorl.
                                                                          Source: wikipedia

The methods were successfully tested with data from the laser scanning of a maritime pine (Pinus pinaster) stand in South Africa. The automatic determination of the branchiness from terrestrial laser scanning was possible with high levels of accuracy for the most valuable part of the stem. The forest industry in South Africa is interested in a TLS based inventory for pine plantations. The new method should supplement and eventually replace the current inventory procedure.

This development provides another building block for the measurement of single trees, forest stands and entire forests for the forest praxis in Germany. In the future, the diameter of braches shall also be determined.