Errors in Estimating Timber. 169 



1. Measuring the breast high diameter of every tree on the 

 area more than 12 inches in diameter. 



2. Measuring the heights of a sufficient number ,of trees for 

 reliable height curves. 



3. Running valuation survey strips, one chain wide, at inter- 

 vals of 10 chains. 



The diameters of the trees were measured with Biltmore sticks, 

 checked up frequently with diameter tapes. In order to avoid 

 measuring the same trees twice, the lines were run in strips and 

 the outside strip on every trip was marked with white chalk or 

 crayon. There were 18,072 trees on the area, 12 inches and over 

 in diameter, an average of 28.2 trees per acre. Only compara- 

 tively few trees were more than 42 inches in diameter. 



It was, of course, impracticable to measure the height of every 

 tree on the area with a hypsometer. A sufficient number of 

 heights of the different species was therefore taken to furnish 

 the data for a reliable curve. Height measurements were taken 

 on over 1,000 trees well scattered over the entire area and repre- 

 sentative of all the types and situations found on the area. These 

 were then curved and a local volume table was' constructed for 

 each species from the regular District volume tables. 



After all the trees on the area were measured land a sufficient 

 number of heights were obtained, the work of estimating the 

 timber was begun. The total tract of 640 acres was divided into 

 five lots', as below. 



It would have been more satisfactory to have divided the area 

 into 40 acre tracts, and estimate and compute each forty sep- 

 arately. This, however, was impracticable for various reasons. 



Strip lines were run 10 chains apart twice through a forty. 

 By taking only one of these strips through each forty, a 5 per 

 cent estimate of the timber was obtained. By taking the other 

 strip through each forty, a second 5 per cent, estimate was ob- 

 tained. By combining these two strips', one gets a 10 per cent, 

 estimate. In estimating the timber, the personal equation of 

 the cruiser was eliminated as far as possible. Most of the di- 

 ameters were measured, the hypsometer was frequently used, and 

 the distance from the compass line to the edge of the strip was fre- 

 quently paced or measured in order to get the proper width. The 

 crew consisted of the most experienced reconnaissance men in the 

 District. 



