272 METHODS OF TIMBER ESTIMATING 



On larger areas, where it would be impossible to keep track of the 

 individual trees, parallel strips may be run. The trees on the outer 

 edge of a strip 'can be blazed facing the strip which has not yet been 

 measured, and in this way the entire tract covered with a minimum 

 of effort. In dense swamps men may be employed to hew parallel 

 lanes through the underbrush; the cruiser then estimates all trees 

 between these lanes. 



It is possible to dispense with all methods of marking the trees 

 provided sufficient care is taken, first, in running the strips accurately 

 as to direction so that they lie parallel and at fixed distances apart, 

 and second, by estimating or measuring the trees on strips so placed 

 that they cover the entire area; i.e., strips whose borders are contiguous. 

 There is danger of overlapping or duplication by this method, and if 

 it is the intention to run a 100 per cent estimate, a slightly greater 

 accuracy can be insured by blazing. This ocular method, however, 

 is commonly employed as a substitute for blazing. 



A modification of this method of completely covering the area by 

 strips, is the laying out of rectangular plots whose dimensions are such 

 as to cover the area without overlapping. These plots are estimated 

 consecutively and may be of any convenient width and length. As 

 an example, a method given in Graves' Mensuration, page 196, consists 

 in laying out two tiers of plots, each 40 rods wide and 16 rods across. 

 Ten of these plots give the area of 40 acres. The cruiser proceeds 20 

 rods from the corner of the forty, and then crosses the center of the 

 first tier of five plots, returning through the center of the second tier. 



To get the contents of the trees on areas 100 per cent of which is 

 estimated, the following systems may be used: 



1. Tally the merchantable contents of each tree directly. This 

 is estimated by eye, or from a universal volume table which may be 

 printed on a Biltmore stick, or any other convenient form. 



2. Tally the upper diameter, inside bark, of each log in the tree, 

 or tally the upper diameter of the butt log and top log (see Rule of 

 Thumb by F. R. Mason, §204). The contents are then computed 

 from a log rule. 



3. Tally the diameter and merchantable height in 16- or 32-foot 

 logs or half-logs of every tree. The contents are then computed from 

 a volume table based on similar dimensions. 



4. Tally the diameter only, of every tree, either by eye or by the 

 use of calipers. Measure, by a hypsometer, several sample trees of 

 each diameter to give a curve of average height on diameter. The 

 contents of the trees are then computed from a volume table based 

 on diameter and height. The heights measured may be either merchant- 

 able or total, but are usually the latter. In this method, types or areas 



