26 PRELIMINARY CALCULATIONS 



Explanation. — The Spaulding Rule is well adapted for Pacific Coast timber. 

 The original Spaulding Rule was based u[)on diagrams but the following 

 rule of thumb gives approximately the same result. 



Vol = (/^-— 3D)— plus 3 per cent to G per cent of the value obtained by 

 this formula. 



D R H -I--D R H 



where D = — '—^ — — - — '- '- — and in which the D.B.H. is the diameter breast 



high inside the bark, in inches. 



L = length from top of stump to point at which diameter inside bark is 

 equal to one-half the D.B.H. inside bark. In practice it makes 

 little difference whether this length be estimated with the 

 \ D.B.H. point taken as one-half the D.B.H. outside the bark or 

 one half the D.B.H. inside the bark as long as both measurements 

 are taken either inside or outside the bark. 



The first part of the fo nula, namely that without the addition of the 

 3 to 6 per cent will give thv. volume of the tree up to the \ D.B.H. point. 

 The additional 3 to 6 per cent will give the value of the merchantable portion 

 of the tree above the \ D.B.H. point. In the case of trees with very tapering 

 tips above the \ D.B.H. point, the lower percentage, namely 3 per cent, should 

 be used, while for trees without excessive taper above the \ D.B.H. point a 

 higher percentage, up to 6 per cent should be used. To compute the volume 

 by this formula two measurements of the tree are necessary, the D.B.H. 

 and the length from stump to \ D.B.H., which will be obtained as outlined 

 in the method of procedure. 



Directions. 



A. Parties. — Men will be organized in two-man parties, each man alternating 



as cruiser and tallyman. 



B. Equipment Required per Party. 



1 pair tree calipers. 



1 hypsometer. 



1 dendrometer (if available). 



1 field note book supplied with Form 3 A, 



C. Method of Procedure. 



Method 1. — By tallying D.B.H. and merchantable length for each tree. 



1. Caliper D.B.H. outside bark of the trees whose volumes are to be 



computed. 



2. By estimate determine width of bark at breast height, and check 



thickness of bark occasionally by chipping through it. 



