Citation:

Cline, S., W. Burkman, AND C. Geron. USE OF QUALITY CONTROL PROCEDURES TO ASSESS ERRORS IN MEASURING FOREST CANOPY CONDITION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/D-89/105 (NTIS PB90113770), 1989.

Description:

Quality control data collected during the measurement of ponderosa pine canopy cover and sugar maple crown damage was analyzed. easurement precision (root mean square of differences in replicate measurements) of pine canopy cover was high (+2.6-4.0%) was similar for field replicates and laboratory replicates digitized with the same and different f-stops. n contrast, significant systematic errors can be introduced during certain analyses of hemispherical photographs. Measurement precision (frequency of remeasurement within +1 class) of maple crown ratings was high (74-95%), due mainly to crew training prior to data collection. recision was highest for branch dieback and foliage transparency and when remeasurements were done by the same crew. sing the same crews for remeasurements and emphasis of branch dieback would increase precision of data collected subsequently, but the cost of these actions should be evaluated in relation to net gain in precision and the biological importance of the response variable. The following procedures are recommended: implement training prior to data collection, use consistent methods and reference materials to control measurement errors during data collection, and include methods and quality control data with study results to provide a basis for evaluating data quality and comparability with other studies.

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