Accuracy of the line intersect method of post-logging sampling under orientation bias

The Line Intersect Method of Post-Logging Residue Sampling is used extensively as a means of estimating waste volume on a clearfelled stand. Whilst the performance of the method under non-random spatial log arrangement conditions has been examined in the literature, similar examinations of method performance when the logs have a non-random orientation distribution have not been rigorously attempted. Thus, a corrected analytic approach to the calculation of expected sampling error under conditions of log orientation angle bias is presented, along with a correction to the Line Intersect Method literature, A simulation model is also used to calculate the standard deviation of the sampling error under orientation bias conditions. The two models are then used to examine the Line Intersect Method in the context of a typical New Zealand stand of Pinus radiata, comparing and evaluating the performance of the method under four patterns of line arrangements and varying line lengths. Our principal conclusion is that the fan and L arrangement provide considerable protection against the effects of orientation bias, although the presence of an orientation bias can considerably increase the size of the likely measurement error.