The two-phase sampling finally 
Estimate of total volume: v - A. X v. x (plot area) i35 
p 
Plot volumes are obtained from a regression, of the type Y - bc (in 
which c =, c', and c' - crown area in per cent per plot; Y - volume, 
(4) b = regression coefficient). 
n 
g 
X6 
i 
Regression coefficient: b = ——— 
  
n," Bumber of field plots used for regression calculation 
n' = number of photo plots 
- 3 E 
va = mean volume of Bg plots (m /plot) - b cn 
(5) P no sap 
pren mere Je, 
ce = f lot = 
on Ac n mean crown cover o % plots (%) = 
p p 
ci - V. crown coves per plot (%) 
n, = number of photo plots for determination of 
v and © 
n n 
p p 
- 3 
Estimate of total volume ve = Ac . b . ca (DB) su Adi een CO) 
p 
2 2 2 -2 2 
(6) Estimate of variance of mean volume: ss = bh" SZ + c i$ . £10) 
n n b 
p p 
2 2 
- 2 
(7) Dui So e $8 
n n v.c 
ER RA. P 
n, n Ch 
g 
2 | 
in which an estimate of the (standard deviation) of c. | 
  
n 2 | 
p | 
n S. c | 
(8) p 2, ©; 
$e 7 
=. p 
n (n - 1) 
p