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A COMPARATIVE TEST OF UNRESTRICTED,
STRATIFTED, TWO-PHASE AND TWO-STAGE
PPS TIMBER VOLUME SAMPLING USING
AN ORTHOPHOTO MOSATC
by
\ *
D.A. Stellingwerf
General
In this part are given the formulae which are used for the calculation of
volumes and standard deviations of spruce plus fir as resulting from four
different sampling methods carried out on a forest area of 10,000 hectares
in Austria.
The unrestricted random sampling
Estimate of total volume: v,- A, xvx (plot area) (m°) 2:03 0.70. X4)
t
v
= i
Estimate of mean volume : v = BR (n5 /plot)
MS
n : number of plots in sample
Vy : volume (a3) in plot i
Ac : total conifer area (spruce + fir) (ha)
y4- X |
i 2
Estimate of variance : S - 2 (Ac) . . . . 00 + . . (2)
(n-1)
The stratified sampling
T
- 3
Estimate of total volume : vr S. Pii (plot area) (m) . . . . . . .(3)
n.
J
v
= ij 3
Estimate of mean volume per stratum j : vs de ra (m /plot)
j
*Ir D.A. Stellingwerf, Professor Forest Survey, Chairman Division of
Natural Resources, Head Department of Forestry, International Institute
for Aerial Survey and Earth Sciences, Enschede, The Netherlands.