A PROPOSED STANDARDIZATION OF THE CHECKING OF 

 VOLUME TABLES 



By Donald Bruce 



Division of Forestry, University of Washington 



There is need for a better and more uniform practice in checking 

 volume tables. In the past they have too often either been accepted 

 unchallenged or have been tested in a rather perfunctory and inade- 

 quate way. As a result there is to-day a wide difference of opinion as 

 to the value of many of even the most modern tables, and those who 

 believe in the accuracy of any one of them can rarely support their 

 opinion by satisfactory evidence. 



Checking in the past has apparently been restricted in the main to 

 the case where it is desired to use a volume table in some region other 

 than that for which it was constructed. It has hence consisted in 

 measuring a score or more trees in the new region and comparing 

 their total volume as scaled with that read from the table for the 

 same number of trees of corresponding sizes. Such a test has its value 

 but it is both uncertain and inadequate, and it should be considered as 

 investigating not the accuracy of the table itself but its applicability to 

 a given stand. 



Before we try to ascertain whether a volume table will accurately 

 apply to the trees of an alien region we should inquire how well it 

 measures the very trees on which it has been based. To borrow a 

 simile from surveying, we should know the precision with which the 

 base line has been determined before we calculate the accuracy of 

 computed distances between far-off triangulated peaks. The first and 

 fundamental checking which a volume table should receive is that 

 against its own basic data. 



The most obvious test of this nature is of course a comparison be- 

 tween the total actual scaled volume of all the trees from which the 

 table has been prepared with that given by the table for the same 

 number of trees of equal sizes. In making this test it should not be 

 necessary to interpolate between the tabular values for fractions of 

 inches in diameter or fractions of logs in height as there is every reason 

 to expect satisfactory compensation of any errors resulting from an 

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