276 METHODS OF TIIMBER ESTIMATING 



increase in the per cent of area, which is easily obtained by increasing 

 the width of the strip without an appreciable increase in the cost. This 

 is independent of the need for running more strips per acre, by which 

 the per cent is still further increased. With unobstructed vision, a 

 wide strip may be estimated with almost as great accuracy as a narrow 

 strip, since the error may be in proportion to the total width without 

 affecting the percentage of error in the estimate. 



With increasing openness and irregularity of timber, strips may 

 give way altogether to a total count of timber on an entire forty, 

 since no system of partial or sample estimates can be depended upon to 

 secure an average or a correct total. 



The method of determining the volume of the trees on the strip 

 affects the width of strip which can be used accurately. Where trees 

 are counted, without measuring the diameter of each tree, nearly 

 double the width of strip can be used because trees can be seen for 

 this additional distance while it is less possible to judge their diameters 

 accurately. Upon a calipered strip, the additional width sometimes 

 slows up the work and introduces a greater per cent of error. 



The counting of trees in open country is so simple a matter that 

 cruisers accustomed to estimating such species as longleaf pine in the 

 South have usually abandoned the strip method altogether. Guided 

 by the compassman, they cross a forty about twice, pursuing a 

 snake's course back and forth, and attempting to see and roughly to 

 count all of the trees on the forty. 



221. Method of Running Strip Surveys. Record of Timber. 

 Strips are universally run with the compass. A hand compass is com- 

 monly used by cruisers working in dense, swampy or brushy country, 

 as it is more quickly read and increases the number of sights possible 

 without delaying the work. For ordinary accurate surveying, in which 

 a topographic map is made, the use of a staff compass adds to the accu- 

 racy of the direction of the strips, and is commonly employed (Fig. 

 58). In the use of either hand or staff compasses, it is a great advan- 

 tage to be able to turn off the declination of the needle on a movable 

 arc with a vernier so that a cardinal direction is indicated by the sights. 

 This is especially true in the Pacific Northwest, where variations up to 

 25 degrees are encountered. 



The size of the field party for strip estimating depends upon the 

 methods used in measuring and recording the timber. Wliere the 

 diameters of each tree are measured either with the calipers or Bilt- 

 more stick, the party will consist of three or four men to best advantage. 

 One man runs the compass and makes the topographic and type maps. 

 A second man tallies the diameters; the thjrd and fourth work, one 

 on each side, calipering trees. Heights are usually taken at regular 



