double sampling method was used successfully in the past on 
similar problems.” The location of each l-acre sample plot was 
determined by locating the lake closest tothe center of the selected 
township that would accommodate seaplane landings and takeoffs. By 
using a National Forest type map, the spruce-fir stand (1 acre or 
larger) nearest the lake shore in a clockwise direction from north 
was selected for the sample. 
Later on, data was strengthened with the addition of photographic 
and ground samples from 24 1-acre permanent study plots located in 
eight additional townships within the mortality area. For analysis, 
data from all 49 plots were treated as arising from a random 
sample. 
All 49 study plots were photographed in July 1962 with a 
Hulcher* 70-mm. aerial camera‘ using Super Anscochrome * ASA 
125 color film at a scale of .1:1584 (2 chains per inch). A Cessna* 
195 equipped with floats was used for the aerial platform. 
Two photomeasurements were used to arrive at volume 
estimates of mortality in spruce-fir stands: (1) average 
stand height, measured with a parallax bar to the nearest foot, and 
(2) crown closure percent of dead host species, calculated from a 
dot template having 144 dots per square inch. A detailed report of 
the photomethods’ used is being prepared and will include the de- 
velopment of prediction equations and resulting cubic foot aerial 
volume tables used in this study. 
Three experienced photo-interpreters at Beltsville were as- 
signed to make the photomeasurements. The variations in measure- 
ments among them were so small that one interpreter would be 
adequate to make similar measurements in the future. 
RESULTS AND DISCUSSION 
The mean volume mortality estimate from the 49 plots was 
221 £ 55 cubic feet per acre, as derived from the regression based 
?Heller, R. C., and Schmiege, D. C, Aerial survey techniques for the spruce 
budworm in the Lake States, Jour. Forestry 60: 525-532, illus. Aug. 1962. 
Aldrich, R. C. A study to determine the possibilities of aerial color pho- 
tography for. following the trend of an insect outbreak, 1962. (Unpublished 
progress report on file at Beltsville Forest Insect Laboratory, U.S, Forest 
Serv., Beltsville, Md.) 
°The mention of commercial products does not imply endorsement by the 
U.S. Department of Agriculture, Forest Service, 
4Heller, R. C., Aldrich, R.C., and Bailey, W. F. Evaluation of several camera 
systems for sampling forest insect damage at low altitudes, Photogrammetric 
Engin, 25: 137-144, illus, March 1959, 
