Mätning av stamdiameter med markstående scanner

Booth for operational planning of harvesting and for long term planning, data is today collected manually. Intensive objective field inventories are usually too expensive. To enhance optimisation of timber flow from forest to industry Moore efficient methods for measuring tree stems of standing trees are needed. The performance of terrestrial laser scanners have improved and these could possibly be used within forestry in the future. The objective of this study was to validate how a terrestrial laser scanner could be used to measure stem diameter, and to test how the errors depend on distance from the scanner and tree species. Two plots (one pine and one spruce) were used for this study. The plots were circular with one tree in the centre that was visible from as many directions as possible. The plots were divided into different directions according to the direction in which the laser instrument was pointing. The trees were measured (circumference) and they were numbered individually. The laser instrument was an Optech ILRIS 3D. Tree diameter was underestimated, with a greater bias for spruce than for pine. The accuracy was validated for trees at a range of up to 60 m distance from the laser instrument. The errors increased with increase in distance. For every tree at <30 m distance, the bias was –14 mm and the relative error was 11 % (pine 7 %, spruce 15 %). In this attempt, a four year old laser instrument was used. Technical developments will result in new instruments that have better precision and are faster, and the price will probably decrease. These arguments indicate that terrestrial laser instruments will be useful for forest inventory activities in the future. Keywords: terrestrial laser, stem diameter, forest inventory.