© 1996 Heron Publishing—Victoria, Canada
Measuring tree-ring increments on tree bole sections with a video-based robotic positioner
R. A. Schmidt (1), Merrill R. Kaufmann (1, 2), Laurie Porth (1) and Ross K. Watkins (1)
1. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO 80526, USA / 2. Author to whom correspondence should be addressed / Received February 22, 1996
Summary
We report on the design and performance of a system that speeds measurement of radial tree-ring increments on tree stem disks;
this method replaces the usual binocular microscope with a video image, and automates the measuring and recording processes.
The system was used to measure bole sections cut from stems at various heights to determine volume growth of representative
trees in an old-growth ponderosa pine stand. The objective of the measurement system was to speed acquisition of annual growth
increments from a large number of disks. A personal computer controls the location of a video camera in a 3-axis positioning
system. The operator views the sample on a video monitor and positions the camera over each ring by selecting it with a computer-driven
mouse. The computer measures and records the distance that the camera moves between each ring. Task selection is facilitated
by menu-driven software that also formats, checks and organizes data files. Measurements have a resolution of 0.026 mm; however,
finer resolution could be obtained with a different camera lens. Tests of measurement variability (repeated measurements by
individual operators on a single radius) indicated standard errors of 0.006 mm or less for the first measurement sets for
four operators. Correlation coefficients among four radii per bole section were as low as 0.66 for a whole tree, suggesting
that measurements on single radii may provide poor estimates of radial growth for old trees. This system also offers the potential
for automatic ring detection and measurement.
Keywords:
dendrochronology, radial increment, stem analysis, tree-ring measurement.
