Comparison of Nearest Neighbor Methods for Estimating Basal Area and Stems per Hectare Using Aerial Auxiliary Variables
Abstract:Simulations were used to compare variable-space nearest neighbor methods for imputing stems per ha and basal area per ha (ground measured) for complex stands (many species and sizes) of southeastern British Columbia, Canada. Species composition and other characteristics obtained for every stand by interpreting aerial photography were used as auxiliary variables. The simulations included three distance metrics (squared Euclidean distance, most similar neighbor, and absolute distance), three intensities of stands with full information (20%, 50%, and 80%), two sets of aerial variables (mixed versus moderately high correlations with ground variables), and three averaging methods (nearest neighbor, average of three nearest neighbors, and distance weighted average of three nearest neighbors weighted). Increasing the number of stands with full information to 50% from 20% resulted in increased accuracy, with no noticeable improvement with a further increase to 80%. Of the three distance metrics, the most similar neighbor measure gave good results in imputing stems per ha and basal area per ha, particularly when there was a mixture of correlations, high and moderate, between the auxiliary (aerial) variables, and the ground variables. No large gain was noted in using the average of three neighbors rather than a single neighbor. FOR. SCI. 51(2):109–119.
Keywords: MSN; environmental management; forest; forest inventory; forest management; forest resources; forest sampling; forestry; forestry research; forestry science; imputation simulations; k-NN; natural resource management; natural resources; nearest neighbor
Document Type: Regular Article
Affiliations: 1: Department of Forest Resources Management University of British Columbia 2045-2424 Main Mall Vancouver BC Canada V6T 1Z4 Phone: (604) 822-4770;, Fax: (604) 822-9106, Email: Valerie.LeMay@ubc.ca 2: Department of Forest Resources Oregon State University 237 Peavy Hall Corvallis OR 97331-5703 Phone: (541) 737-8549;, Fax: (541) 737-3039, Email: email@example.com
Publication date: April 1, 2005
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