Forest Service Office of Fire Control, State Forest- 

 ers of Oregon and Washington, Indian Service, 

 and private fire-patrol associations. 



Checking and Adjusting Timber Estimates 



After all available private and public timber 

 cruises had been collected, the next step was to bring 

 each individual cruise to the specifications set up 

 by the Forest Survey. This step, known as check 

 cruising consisted in cruising sample areas covered 

 by the original cruise according to survey standards 

 and computing an adjustment factor from a com- 

 parison of the original and check cruises. The 

 sample areas, usually 320 acres in extent, were so 

 distributed throughout the area covered by the 

 original cruise as to give a representative check 

 on 2 to 5 percent of the total acreage. 



In cruising, quarter-acre circular plots were 

 taken at 2^-chain intervals along compass lines 

 run twice through each 40-acre tract, making a 

 total of 16 such plots and giving a 10-percent 

 cruise. All cruise lines were carefully referenced 

 to section and quarter-section corners, assuring the 

 same coverage as the original cruise. Volume was 

 recorded for all trees 11.1 inches d. b. h. and larger 

 on the plot and the locations of all doubtful-line 

 trees were determined with a tape. All large 

 trees were measured for diameter with a tape and 

 sufficient smaller trees were measured to check the 

 cruiser's estimate of diameter. Tree heights to a 

 utilizable top were obtained with the Abney level 

 and by taping an occasional windfall. Deduction 

 for breakage and defect in each species was made 

 for each 40-acre tract. All beetle-killed ponderosa 

 pine trees were recorded by diameter class, and 

 the number of poles — trees 5.1 to 11.1 inches 

 d. b. h. — was also recorded by species for each 

 40-acre tract. 



The check cruises were compiled currently in 

 the field and were compared with the original 

 cruise. Through this comparison the check cruiser 

 was able to determine when sufficient samples 

 had been obtained to give a reliable adjustment 

 factor. 



Whenever records were available, a comparison 

 of actual cut and original cruise was made. The 

 results of this comparison provided a good check 

 on the adjustment factors set up for that particular 

 cruise. 



Type Mapping 



The accuracy of the resultant type map was 

 very largely dependent upon the detail and ac- 

 curacy of the base data. In most counties in the 

 region, the land survey was from 50 to 70 years 

 old and section corners and lines were usually 

 difficult to locate. Although the mappers checked 

 on corners whenever these could be readily found, 

 they depended greatly on the base-map location 

 of roads, trails, streams, and triangulation points 

 for orientation. 



The volume per acre and composition of all 

 previously uncruised saw-timber stands were esti- 

 mated ocularly by mappers, who frequently checked 

 their judgment by taking a series of equally 

 spaced %-acre sample plots along a compass line. 

 The mapping of a county was assigned to a party 

 chief with from one to five or more assistants. 

 Usually a township was entirely mapped by one 

 man. Daily coverage varied widely depending 

 upon accessibility, topography, and density and 

 character of the timber. 



Mapping procedure consisted of working in cars 

 along roads, on foot along trails, ridges, and 

 random compass lines, and of using all lookout 

 stations and points. In mature and selectively 

 cut stands much of the mapping was done by 

 running random strips. All mapping was done 

 on 1-inch-to-the-mile township forms of transparent 

 vellum. These vellums were overlaid on a base 

 map of the township prepared through the enlarge- 

 ment of the most recently revised %-inch-to-the- 

 mile lithographed national-forest base map. These 

 national-forest maps were found to be the most 

 accurate and covered the bulk of the forested por- 

 tion of the region. In two of the Indian reserva- 

 tions, not completely covered by national-forest 

 base maps, maps prepared by the Indian Service 

 were used. For regular townships standard town- 

 ship forms of vellum were used for the mapping 

 overlay sheet; for irregular townships the section 

 lines and quarter lines were drafted on a blank 

 sheet of vellum. 



Type boundaries as determined were placed 

 directly on the vellum overlay by the use of sym- 

 bols indicating the type, composition, and volume 

 per acre of saw-timber stands, and the type, com- 

 position, age, and degree of stocking of immature 

 stands. 



86 



