Evaluation of the Laser-relascope

The second prototype of a new measuring device, the Laser-relascope, was tested under typical forest conditions. The Laser-relascope is functionally a combination of a relascope and a dendrometer. It uses distance and angle information to determine the diameter of a tree. The distance between the device and a tree is measured with a laser instrument. In addition to a laser rangefinder. the Laser-relascope includes a variable-width slot with a fixed-length arm, an electronic compass, an electronic inclinometer. a data collection/processing unit, and a GPS receiver. In this study, diameters, heights. and distances (bearing and distance from the center of a sample point) of trees were measured. Furthermore, sample points can be located by using the GPS receiver. With the use of a Laser-relascope, diameter measurements were almost unbiased (overestimation 1.3 mm). with measuring distances of 1.4-15.0 m. The standard error was 8.2 mm. The accuracy was dependent on the distance. the slot width. measuring, time of a tree, and the diameter at breast height (dbh). The individual's familiarity with the Laser-relascope, also had an effect on the precision of diameter measurements. In height measurements. the device produced unbiased results. The standard error was 4.9 dm. Locations of trees could also be determined with good precision. The mean distance between the observed and correct location was 32 cm. The measurements of the height and location were not affected by experience with the device. The precision of volume estimation was dependent on the basal area and the time needed to measure a tree. Measuring a sample point took on average 15.5 min and the measuring of a single tree 85 s. Measuring time was dependent on basal area, visibility. and dominant species. The device can be used throughout the day with moderate strain. It is most suitable for near mature forests with good visibility. (C) 2004 Elsevier B.V. All rights reserved.