Photo and field plots were located systematically. Plot centers were pinpricked approxi- 

 mately 1 ,320 feet west of the principal point of each aerial photo lying within the sampled tract. 

 Plot intervals averaged about 1 .0 mile east and west and 1 .5 miles north and south, throughout 

 the area. Plots were numbered consecutively and marked on the existing type and stand-class 

 map for the area, and on the USGS quadrangles. 



Photo measurements for the dominant stand consisted of total height and crown diameter 

 in feet, and crown cover in percent. Height and crown cover were also recorded for the under- 

 story in two-storied stands. Stand-height measurements were made under lens stereoscope 

 using parallax wedge. Crown cover was measured by a crown-density scale. Measurements 

 of slope percent were also made through each plot center. These stand measurements were 

 converted to gross cubic- and board-foot volumes per acre using an aerial volume table (6). 



In addition to the measurements several photo interpretations were made. These inter- 

 pretations of species -type, stand size, topographic site, and aspect, were primarily subjective 

 although the stand measurements and volumes were used in making them. Insofar as possible 

 Forest Survey definitions were used for these photo classes. 



Photo measurements and interpretations for the 1-acre plot surrounding each pinpricked 

 location were recorded on 3- by 5-inch cards. Also included were plot and photo flight line 

 numbers, elevation, photo scale, and parallax factor. 



To assure independent observations all photo interpretations were made and recorded 

 prior to any field examination. All field classifications and measurements were made inde- 

 pendently from photo interpretation except that field plots were located by means of the same 

 aerial photos previously measured by the photo interpreter. The pinpointed plot centers were 

 located as precisely as possible on the ground and formed the starting point for location of the 

 16-point field sample grid described below. 



Stand volume and tree distribution were obtained from a grid of 16 points located on each 

 1-acre sample (8). Pole and seedling- sapking volumes and counts were determined on a 1/256- 

 acre fixed plot around each grid point . Sawtimber volume was obtained from variable plots 

 located at each of the 16 points and averaged for the acre location. Detailed description of 

 crop trees, a measure of competition, and a quantitative estimate of excess trees were also 

 obtained from the grid plots. Finally, a qualitative description of sawtimber was recorded as 

 a basis for risk classes. 



Using these data and Forest Survey volume tables, we determined cubic- and board-foot 

 volume for each acre sample. These volumes, together with the following data, were also 

 recorded on each 3- by 5 -inch photo plot card: 



AERIAL PHOTO DATA 



FIELD DATA 



average) 



Total stocking and desirable tree stocking 

 Field stand- size class 



Tree and stand heights (tallest, five tallest 



Field category 

 Field site class 

 Management prescription 

 Aspect and slope percent 



4 



