Digital Signal Processing Reference
In-Depth Information
Table 8.2
Permittivity of some soil surfaces as calculated for
frequency = 1.5 GHz, using the semi-empirical model in
Ulaby et al.
(
1986
,
E.111, p. 2103), setting the bulk soil density to 0.5 (consistent with
Krotikov 1962
)
Soil composition
Volumetric moisture
Real part of the
Sand (%)
Silt (%)
Clay (%)
.V
w
et
=V
total
/
dielectric constant
51.1
35.0
13.5
0.0
1.55
0.1
4.67
0.2
9.22
0.3
14.95
0.4
21.74
0.5
29.49
42.0
49.5
8.5
0.0
1.55
0.1
4.66
0.2
9.20
0.3
14.92
0.4
21.70
0.5
29.45
30.6
55.9
13.5
0.0
1.55
0.1
4.47
0.2
8.85
0.3
14.44
0.4
21.13
0.5
28.84
17.2
63.8
19.0
0.0
1.55
0.1
4.27
0.2
8.47
0.3
13.91
0.4
20.50
0.5
28.16
5.0
47.6
47.4
0.0
1.55
0.1
3.80
0.2
7.56
0.3
12.63
0.4
18.95
0.5
26.46
grazing angles of elevation (large incidence), the reflection is essentially co-polar:
RCHP signals are reflected as RHCP. The transition between the co-polar and cross-
polar regime is characterized by the Brewster angle, in which only horizontally
polarized signal is scattered, and thus the RHCP and LHCP must have the same
power (otherwise yielding elliptically polarized fields). The polarimetric features of
the scattering around the Brewster angle are sensitive to the dielectric properties
of the surface, especially for soil moisture (Brewster angle in the soil example
shown in Fig.
8.13
presents variations between 58
ı
and 80
ı
incidence, for soil dry
to 0.5 volumetric moisture). Sea water is in general more reflective than soil, but
less sensitive to dielectric variations (given by salinity and Temperature), than soil
moisture changes.
Search WWH ::
Custom Search