ne
Li
e
Trees &
nc
Brush
Fe
ld
Trees &
O
Brush
Transect 6
Transect 5
Brush
e
er Lin
) Wat
Inner
6 cm
7.
3 in. (
Bunker
Transect 3
Trees &
Brush
Transect 2
Outer Wall
Transect 1
N
200 ft
150
100
50
0
40 m
20
0
Figure 5. Layout of GPR transect lines at transmitter site. Transects discussed in this report are labeled. Arrows
show direction of transect. Dashed lines show other transects run during study.
d = ct / 2 ε
tivity, which determines the in-situ velocity, is
known. Clusters of diffractions can originate from
natural and man-made objects and often point to
where c = 30 cm/ns, the speed of radio waves in a
vacuum, and ε is the relative dielectric permittiv-
a target of interest. Strong horizontal reflections
originate from the water table and various
ity of the soil. The factor of 2 accounts for the round
subhorizontal horizons, including continuous soil
trip propagation of the pulse, to and from the
layers that contain more water than found in the
reflecting surface.
surrounding materials.
The dielectric permittivity of the soils at the
All GPR profiles presented in this report show
transmitter site was determined from the time
distance along the transect as the horizontal axis
distance slope of hyperbolic diffraction asymp-
and the two-way travel time (t) increasing with
totes. Permittivity was determined in June 1996
depth down the vertical axis. Travel time may be
and yielded a mean soil permittivity of 11.3. The
converted to depth d according to
soil surface was dry and frost was absent. With
6
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