Agriculture Reference
In-Depth Information
- 10
resolution:
6.25 m x 6.25 m
resolution:
6.25 m x 6.25 m
10
June 10, 2006
May 28, 2006
-15
8
6
-20
4
r
2
= 0.807
-25
r
2
= 0.867
2
0
-30
Palsar (L band - HH)
~ 1.3 GHz = 23 cm wavel.
~ 4.6 cm depth
Radarsat (C band - HH)
5.3 GHz = 5.7 cm wavel.
~ 1.1 cm depth
-2
0510
15
20
25
30
35
0510
15
20
25
30
35
gravimetric soil moisture in %
gravimetric soil moisture in %
Fig. 5.18
Reflection of radar microwaves back to the emitting satellites depending on the mois-
ture content of bare soils. The backscattering coefficient on the y axis indicates the ratio between
the wave power that is backscattered to the satellite and the incident wave power. This ratio of wave
power is usually expressed in decibel (dB). The latter is ten times the common logarithm of this
power ratio. Any negative values result from common logarithms below 1 (From Balik Sanli et al.
2008
, altered)
similar way as georeferencing from satellites today is state of the art. However, such
continuous signal transfer from the satellites to farm machines is not yet possible.
Since radar satellites are not operating in a geostationary mode but instead orbit in
a polar mode, this would require the availability of many more satellites in order to
provide a continuous signal transfer. Furthermore, a network that links satellites,
processing and farmers would be a prerequisite.
5.2.3.3
Water Sensing from Field Vehicles by Permittivity
This mode of water sensing would be attractive in precision farming if it could
occur during usual farming operations and thus be used for simultaneous on-
the-go control. Such a procedure is not yet state of the art, however, not beyond
feasibility.
The emitting and sensing of radar reflectance from a land vehicle - as shown in
Fig.
5.19
- is based on a frequency of 500 MHz. This frequency is below the usual
range that is used by satellites. The lower frequencies and hence longer waves result
in deeper sensing. A sensing depth of about 12 cm can be obtained (see Sect.
5.2.3.2
).
