large limbs. The top log contains approximately seven 

 percent of the volume of the tree, or a reduction of 

 57 board feet if the log had been culled. Had the esti- 

 mator dropped his height estimate a log to allow for the 

 limby top, the volume of the tree would have been recorded 

 as 700 board feeto Thus, in attempting to correct for 

 57 board feet of cull, the tree volume has been reduced 

 by 110 board feet, an underestimate of about seven percent. 



"The second error will result if heights are estimated to 

 a smaller top diameter than specified in the volume table. 

 Estimating usable top to a smaller size causes an over- 

 estimate of tree volume as shown in the following example. 

 A 20-inch ponderosa pine with four logs to a 10-inch top, 

 contains 420 board feet. Suppose local utilization is to 

 an eight-inch top, giving the tree an extra log. An eight- 

 inch log will scale 30 board feet vjhich added to the volume 

 of the four-log tree gives a total actual volume of 450 

 board feet. If the tree had been estimated as a five-log 

 tree to an eight-inch top, and the volume read from the 

 table specifying a 10-inch top diameter, the gross volume 

 vjould have been found to be 530 board feet, an over-estimate 

 of 80 board feet or about 18 percent." 



The use of local volume tables adjusted to fit the conditions for a 

 particular type of timber is superior to correcting individually for 

 each tree. The use of form class volume tables should also be 

 encouraged. Such factors as unusual bark thickness on the lovjer bole 

 and butt swell, caused by various defects, often are sources of errors 

 in volume determinations. An experienced estimator can make adjust- 

 ments of diameter if the tree is malformed and thus bring the estimated 

 volume nearer the scaled volume o 



Breakage 



Breakage introduces discrepancies between estimators' and checkers' 

 volumes which cannot be foretold. Hovrever, breakage usually creates 

 only a minor part of the total error. 



Check scaling standards and methods 



The actual check scaling must, of course, be precise because the cor- 

 rection factor found by a relatively small check scale is applied to 

 a large volume. Scaling in the woods, with logs and debris criss- 

 crossed and log ends concealed, is a difficult job. Where a scale 

 stick cannot be used on the ends of logs, calipers and a bark measuring 



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