Table 4. — Number of photo points and field samples by land class and photo 

 volume stratum within productive forest land East Working Circle, 

 Klamath National Forest 



Land class 



Photo sample 

 stratum 



Number 

 photo points 



Number 

 field samples 



• 



Productive forest 



1 

 1 



91 c. 



Z J. o 



1 7 





2 



818 



58 





3 



518 



32 





4 



546 



25 







fiOfi 







6 



309 



13 





7 



226 



14 





8 



39 



2 



Subtotal 





3,277 



191 



Nonproductive forest 





692 



41 



Nonforest 





342 



16 



Total 





4,311 



248 









photo coverage, 4,311 photo points v^ere classi- 

 fied, giving an area v^eight per sample point of 

 127.8355 acres. 



^ = 127-8355 

 4,311 



The estimate of area by class of land based 

 on the photo samples was as follows: 





Number 







photo 





Land class 



points 



Acres 



Productive forest land 



3,277 



418,917 



Nonproductive forest land 



692 



88,462 



Nonforest land 



342 



43,720 



Total 



4,311 



551,099 



Every nth photo point sample was drawn as 

 a field sample and visited on the ground. Tree 

 measurements were taken only when the field 

 inspection indicated the sample (1 acre around 

 the photo point) was productive forest land. 

 Also, to improve sampling efficiency, produc- 

 tive forest land photo samples were classified 

 into eight sampling strata prior to field 

 sampling. 



Table 4 shows the total number of photo 

 and field samples by class of land and by sample 

 stratum for the Working Circle. As mentioned 

 previously, the field sample information was 

 used to verify the classification of land made 

 from photo point interpretation. The results of 

 the field verification were then used to adjust 

 the photo sample area estimates to correct 

 photo sample misclassifi cation. 



Two estimates of area by classes of land 

 were made : ( 1 ) The first one was based on the 

 results of the field classification of sample 

 points selected for field sampling as initially 

 carried out by the timber inventory staff ( table 

 5); the second one was based on a classification 

 of field samples using study criteria. The esti- 

 mates of area by broad land class from the 

 photo point sample were adjusted by using the 

 timber inventory field classification as a base. 

 The results were as follows : 



Land class 

 Productive forest land 

 Nonproductive forest land 

 Nonforest land 



Total 



Acres 

 416,617 

 101,692 



32,790 

 551,099 



27 



