Canadian Forest Service Publications
Assessing Precision in Conventional Field Measurements of Individual Tree Attributes. 2017. Luoma, V., Saarinen, N., Wulder, M.A., White, J.C., Vastaranta, M., Holopainen, M., Hyyppä, J. Forests 8(2), 38.
Issued by: Pacific Forestry Centre
Catalog ID: 38882
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Forest resource information has a hierarchical structure: individual tree attributes are summed at the plot level and then in turn, plot-level estimates are used to derive stand or large-area estimates of forest resources. Due to this hierarchy, it is imperative that individual tree attributes are measured with accuracy and precision. With the widespread use of different measurement tools, it is also important to understand the expected degree of precision associated with these measurements. The most prevalent tree attributes measured in the field are tree species, stem diameter-at-breast-height (dbh), and tree height. For dbh and height, the most commonly used measuring devices are calipers and clinometers, respectively. The aim of our study was to characterize the precision of individual tree dbh and height measurements in boreal forest conditions when using calipers and clinometers. The data consisted of 319 sample trees at a study area in Evo, southern Finland. The sample trees were measured independently by four trained mensurationists. The standard deviation in tree dbh and height measurements was 0.3 cm (1.5%) and 0.5 m (2.9%), respectively. Precision was also assessed by tree species and tree size classes; however, there were no statistically significant differences between the mensurationists for dbh or height measurements. Our study offers insights into the expected precision of tree dbh and height as measured with the most commonly used devices. These results are important when using sample plot data in forest inventory applications, especially now, at a time when new tree attribute measurement techniques based on remote sensing are being developed and compared to the conventional caliper and clinometer measurements.
Plain Language Summary
Characterizing the precision of dbh and height measurements using conventional field methods.Knowing the precision of the reference data is essential when new forest measurement methods and techniques are developed. Conventional field measurements provide precise information from dbh and tree height. Dbh can be measured with greater precision than tree height. Context: Knowing how well field measures are getting heights, we can use this to relate how well we are doing with lidar. The standard deviation in tree dbh and height measurements was 0.3 cm (1.5%) and 0.5 m (2.9%). The precision of measurements was also studied within tree species and tree size-classes. There were no statistically significant differences between the mensurationists in dbh or height measurements. Our study offers insights on the expected precision of the most commonly field measured tree attributes with most conventionally used devices. This is important to take into account when using sample plot data in forest inventory applications and especially now when tree attribute measurement techniques are developed and compared to the caliper and hypsometer measurements.