%0 Research article
%T Anticipating the variance of predicted stand volume and timber assortments with respect to stand characteristics and field measurements
%A Kangas, Annika
%A Maltamo, Matti
%D 2002
%J Silva Fennica
%V 36
%N 4
%R doi:10.14214/sf.522
%U https://silvafennica.fi/article/522
%X Several models and/or several variable combinations could be used to  predict the diameter distribution of a stand. Typically, a fixed model  and a fixed variable combination is used in all conditions. The  calibration procedure, however, makes it possible to choose the  measurement combination from among many possibilities, although the  model used is fixed. In this study, the usefulness of utilizing  additional stand characteristics for calibrating the predicted diameter  distribution is examined. Nine measurement strategies were tested in  predicting the total stand volume, sawlog volume and pulpwood volume.  The observed errors of these variables under each strategy were modeled  as a function of basal area, basal area median diameter and number of  stems. The models were estimated in three steps. First, an Ordinary  Least Squares (OLS) model was fitted to the observed errors. Then, a  variance function was estimated using the OLS residuals. Finally, a  weighted Seemingly Unrelated Regression (SUR) analysis was used to model  the observed errors, using the estimated variance functions as weights.  The estimated models can be used to anticipate the precision and  accuracy of predicted volume characteristics for each stand with  different variable combinations and, consequently, to choose the best  measurement combination in different stands.