302 IMPROVING THE ACCURACY OF TIMBER ESTIMATES 



an accuracy of within 10 per cent. The error should be conservative 

 rather than an over-estimate if possible. Greater errors than 10 per 

 cent may be caused by differences in scaling practice alone, or in the 

 length of logs cut, or the thickness of lumber sawed. 



237. The Cost of Estimating Timber. No figures will be given for 

 the costs of various methods of timber estimating. These must be 

 determined locally. The elements of cost are: 



1. The size of the crew and the wages paid each memljer; the 

 character of supervision, such as the combining of several crews under 

 one supervisor; and the employment of a cook. 



2. Accessibility of the tract as affecting transportation of men and 

 of supplies, especially of food. The means of transportation, such as 

 pack versus wagon haul. 



3. Cost of location of boundaries and surveys and cost of establish- 

 ment of base lines from which strip surveys are to be run. This is a 

 function of the size of the tract and the character of the boundary survey 

 and monuments already established. 



4. The number of strips or miles of line to be run per unit of area. 

 The cost is not exactly proportional to the miles run since certain 

 items such as travel to and from work and from one strip to another, 

 cost of computing the estimate, and cost of mapping in the office, increase 

 in a lesser ratio. Doubling the number of strips increases the cost from 

 50 to 80 per cent, dependent upon the saving in these items. 



5. The rapidity of traverse or number of miles of line which may be 

 run per day. A standard day's work varies directly with topography 

 and brush, and with the amount of detailed work required in the actual 

 estimate along the strip, as determined by the number of products, 

 the number of species, the number of trees and the details of record 

 required. In very brushy and mountainous or precipitous country 

 with a variety of species, 1 mile per day may be all that is possible, 

 varying up to 2 miles. An average day's work in fairly open country 

 varies from 2 to 4 miles; on level open land with sparse timber and no 

 brush, 4 to 8 miles may be made. 



6. The character of the topographic map required. To a certain 

 extent, a detailed topographic map appreciably slows up the work. 

 It is the object of a forest survey to require only that degree of accuracy 

 and detail which will not add appreciably to the cost by delaying the 

 party. 



7. Computation or office work required. By practical cruisers, this 

 is almost eliminated through the methods employed. Methods of 

 tallying dimensions and the use of volume tables increase this addi- 

 tional expense. 



8. Holidays, sickness and lost time. Only the number of hours 



