Abstract
A forest inventory is often carried out using airborne laser data combined with ground measured reference data. Traditionally, the ground reference data have been collected manually with a caliper combined with land surveying equipment. During recent years, studies have shown that the caliper can be replaced by equipment and methods that capture the ground reference data more efficiently. In this study, we compare three different ground based laser measurement methods: terrestrial laser scanner, handheld laser scanner and a backpack laser scanner. All methods are compared with traditional measurements. The study area is located in southeastern Norway and divided into seven different locations with different terrain morphological characteristics and tree density. The main tree species are boreal, dominated by Norway spruce and Scots pine. To compare the different methods, we analyze the estimated tree stem diameter, tree position and data capture efficiency. The backpack laser scanning method captures the data in one operation. For this method, the estimated diameter at breast height has the smallest mean differences of 0.1 cm, the smallest root mean square error of 2.2 cm and the highest number of detected trees with 87.5%, compared to the handheld laser scanner method and the terrestrial laser scanning method. We conclude that the backpack laser scanner method has the most efficient data capture and can detect the largest number of trees.
Highlights
Updated information about forest resources is important on different scales ranging from the individual tree up to regional, national and global levels
The trees are directly positioned in a global coordinate system using a global navigation satellite system (GNSS) aided inertial navigation system in combination with an iterative closest point approach
The study has compared three different laser based methods to extract the diameter at breast height and tree position within seven different plots
Summary
Updated information about forest resources is important on different scales ranging from the individual tree up to regional, national and global levels. Optical sensors on airborne and spaceborne platforms are being used for mapping of forest resources, and, in the boreal forest in the Nordic countries, a majority of operational forest inventories are today carried out using a combination of aerial imagery and data from airborne laser scanning [1]. In this inventory method, the relationship between remotely sensed data and field measured properties is modeled for area units [2]. A requirement in this approach is that field reference data are available. Field reference data are required and used in this case
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