TRAINING REQUIRED TO PRODUCE TIMBER CRUISERS 305 



The tract, when cut, scaled by Scribner Decimal C log rule 314,350 board feet, 

 an error of A of 1 per cent. 



The best system of training men for timber estimating is by the use of sample 

 plots on which the diameter and merchantable heights in log lengths of each tree 

 are estimated by the eye and checked against the records. On these same plots, 

 each of the six classes of averages (§ 209) can then be tested and their application 

 mastered. Each day's training can be checked against the measured volume of 

 the plot that night and not only the total error in per cent but the exact cause of 

 this error ascertained. On this basis, the progress of training is rapid and the 

 cruiser is advanced in a short time more than would be possible in several years of 

 estimating without these checks. The following outline wUl illustrate the possi- 

 bilities: 



1. Plots of 20 acres, 40 by 80 rods, are laid out with compass. The boundaries 

 are marked by blazing the trees facing each of the four sides on the face towards the 

 plot. Stakes are set on all four sides at distances of 20 rods apart. Two plots are 

 laid out adjoining each other, together comprising 40 acres. 



2. Every tree on the plot is calipered at B.H. in two directions, the average 

 being taken to the nearest even inch and the bark blazed to prevent duplication. 

 The blazes are made facing the portion or strip not yet measured. A crew of one 

 tally man and two caliper men are used and all trees above a fixed diameter are taken, 

 corresponding with the minimum exploitable diameter class. 



3. The merchantable heights to the nearest 8-foot length or half-log are measured 

 by two or three additional men with Faustmann hypsometers. From 30 to 40 per 

 cent of all heights can be measured during calipering in this way. Height men 

 work with the diameter crew taking the diameter as measured, pacing for distance 

 from the tree and recording heights based on diameter. Forty to sixty heights 

 per hour can be recorded by each man. Upper diameters or merchantable lengths 

 are based upon the practice of sawing as applied to the species measured, provided 

 this is the basis on which the volume table was constructed. 



4. The determination of the merchantable height of every tree from that of 30 to 

 40 per cent of the trees is made separately for each diameter class. The heights 

 tallied within the diameter class are taken to indicate the percentage or proportion 

 of the different height classes existing in this diameter class and the total number 

 of trees are then distributed according to the same proportion. As the result required 

 is a proper distribution for the plot as a whole, and not for each diameter separately, 

 this method gives a sufficient degree of accuracy. 



5. The record for the plot will show the following data: total estimate in board 

 feet, total number of trees, average stand per acre, volume of average tree, volume 

 of average log or log run per thousand board feet, exact number of trees in each 

 diameter class, exact number of trees in each log and half-log height class independent 

 of diameter. 



The exact number of trees in each separate diameter and height class is the 

 basis for the last two summaries ; but the summaries rather than the detailed class- 

 ification are made the basis of the estimating, i.e., the tally is totaled for each 

 diameter class, and in turn, is totaled for each height class irrespective of diameter. 



For each day's work the cruiser hands in a report on the first five of the above 

 seven items and brings in his notebook in which he has totaled the number of trees 

 for each diameter class and each height class separately. His accuracy is computed 

 as a per cent of the total stand on the plot. The error in per cent is recorded. The 

 sources of error are then examined. These are four in number. 



1. The width of the strip may be too great or too small. This is shown by an 

 error in the number of trees tallied. 



