Agriculture Reference
In-Depth Information
Fig. 6.3 Schematic of end
area method
A 1
L
A 2
A n
V
=
L
×
[( A 1 + A 2 )/2]
(6.4)
where
volume (m 3 )
V
=
area of the grid square (m 2 )
A
=
distance between cross-section along the baseline (m)
Total volume, V T = V i
L
=
Prismoidal Formula
The Prismoidal Formula (PF) allows for greater accuracy than EAM. It is espe-
cially useful when the ground is not uniform or significantly irregular between
cross-sections. PF adds an additional cross-sectional area midway between the two
cross-sections defining the volume being calculated. Note that this cross-section is
calculated separately and is not an average between the two end areas. Volumes are
calculated as follows:
V
=
L
×
[( A 1 +
(4
×
A m )
+
A 2 )
/
6]
(6.5)
where
volume (m 3 )
A 1 , A 2 =
V
=
areas of the adjacent cross-sections (m 2 )
area of the midway cross-section (m 2 )
A m =
=
L
distance between cross-section along the baseline (m)
Contour Area Method
The Contour Area Method (CAM) uses the area of the excavation elevation contour
lines to determine volumes. From a topographic map of the site, the areas enclosed
by regular contour intervals are measured (Fig. 6.4 ) . This area measurement can
 
 
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