While it is true that the number of measured field plots used on extensive management and 

 volume inventories is approaching an irreducible minimum, it is also true that accuracy on the 

 area figures to which data from these plots are applied could certainly be improved through 

 photo measurement. Interpretation of additional photo plots, particularly if these were stratified 

 by the best possible method could improve the reliability of the entire survey. 



Finally, the many considerable photo estimating studies made during the past decade have 

 opened the door to better and less costly methods of localizing extensive management and 

 volume inventories. The opportunity for this use alone should justify more consideration 

 of photo measurements and cubic-volume strata. 



SUMMARY 



A number of photo-and map- stratification schemes were studied using data from the St. 

 Regis test area. Primarily, we concluded: 



In volume estimating, photo-volume classes offer the best means of stratification. 

 Volume classes also appear to offer distinct advantages in stratifying for management pur- 

 poses. Photo cubic volumes obtained from direct photo measurement and aerial volume 

 tables, and stratified into 1 ,000 -cubic -foot classes appear to offer the most practical photo 

 approach to combined management and volume inventories. Some additional findings were: 



1. Photo cubic-volume strata were found to be at least as efficient in board-foot 

 volume estimates as in cubic-foot volume estimates. 



2. The familiar and widely used stratifications of photo or map stand size and density 

 contributed much less to either survey than did cubic-volume strata. 



3. Stand-size and density stratifications based on field data, though somewhat better 

 than their counterparts made on photos, still contributed much less than did photo 

 stratification by cubic volume . 



4. Stand density and site strata, whether obtained from photo , map, or field data, 

 contribute little to the efficiency of volume estimates . Density is helpful in selecting young 

 stands in need of treatment , but both density and site probably contribute most in estimating 

 priority and the amount of work required . 



5. Photo measurement cost 0.27 per man-hour and field measurement 14 man-hours 

 per location. On a survey requiring 100 unstratified field locations, photo stratification by 

 cubic-volume class could reduce field measurement time from 1,400 to 490 man-hours. 

 Forest Survey records indicate dollar costs for field plot measurement may easily be 100 

 times the cost of photo measurement at the same location. For this reason substantial 

 savings are possible in double sampling based on cubic-volume strata. 



15 



