FOREST SURVEY METHOD 



Initial survey - The initial survey of Northeast Washington was made 

 during 1934 and 1935 by the "compilation" method briefly described 

 as follows: The boundaries of nonforest land and forest land 

 classified by type, stand-size, stocking, age and site classes, were 

 delineated on 2-inch-to-the-mile base maps so far as possible from 

 intensive cruises data, county assessment records, fire records, etc. 

 Information for areas not covered by records and for stand character- 

 istics, such as age and site, which could not be determined from 

 available records, was determined by field examination in connection 

 with an overall check of all data. Forest cover classifications were 

 based on prevailing condition on areas of generally forty acres or 

 more . 



All delineated areas were planimetered and area computations were 

 sorted and summarized by classification. The possible number of 

 classes for commercial forest only were 10 (types) x 3 (stand-size 

 classes) x 3 (stocking classes) x 6 (age classes) x 5 (site classes) 

 or 2700. 



Timber volume was estimated for each commercial forest delineation 

 either from intensive cruises adjusted to a common standard, field 

 samples, ocular estimates, or modified normal yields correlated with 

 type, stand-size, stocking, age, and site classes. 



Re survey - The resurvey of the same area was made from 1946 to 19 48 • 

 Nonforest, forest and the various subclasses were derived by correlat- 

 ing initial survey area data with forest cover observed along sample 

 transects. The transects were run in a random direction to and from 

 Land Office section corners spaced at 4-mile intervals. Cover con- 

 ditions were observed, classified, and recorded on a strip two chains 

 wide, a 2x2 chain or 0.4-acre unit being the minimum area considered 

 in the classification. Transect courses, location of section corners, 

 and other information were recorded on available aerial photographs 

 to facilitate relocation and future remeasurement . 



The transect courses were plotted on the initial survey cover maps. 

 Transect classifications were sorted and summarized by initial survey 

 cover classifications. The total area of each initial survey classi- 

 fication was reclassified in accordance with the composition indicated 

 by the transect sample for that classification. 



Three l/5-acre sample plots measured for volume at each location 

 (4-mile intervals) provided the basis for mean-acre volumes by classes. 

 Total volume estimates were derived from the mean-volume estimates and 

 revised areas by classes. 



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