Agriculture Reference
In-Depth Information
r
2
= 0.76
60
50
40
30
20
10
0
r
2
= 0.80
40
30
20
10
vertical profile
top surface
0
0
20
40
60
0
10 0 0 0
measured clay content in %
measured clay content in %
4
4
r
2
= 0.87
r
2
= 0.80
3
3
2
2
1
1
vertical profile
top surface
0
0
0
1
2
3
4
0
1
2
3
4
measured organic carbon in %
measured organic carbon in %
Fig. 5.24
Comparison of predicted soil properties - obtained by traditional analysis - with mea-
sured values from full spectra of visible plus near infrared reflectance sensing in laboratories. The
soil samples were taken either from vertical soil profiles (1.2 m deep) or from top surfaces. For
wavelength ranges see Table
5.4
(From Lee et al.
2009
, altered)
Since the vertical profiles represented not only the topsoil but the subsoil as well,
its properties varied more than those that were taken solely from the top surfaces.
The sensing results for the samples from the vertical profiles were better than those
that were based on the top surfaces (Fig.
5.24
).
The wavelength range that should be used for a full spectrum approach might
depend on the soil properties needed. Lee et al. (
2009
) found that the soil property
estimates from a reduced wavelength range of 1,770-2,500 nm were of similar
accuracy than those obtained from the complete visible plus near-infrared range.
The most important information obviously originates from the upper part of the
near-infrared range. However, Lee et al. (
2009
) did not include mid-infrared reflec-
tance and soil water in their investigations. When it comes to water, near-infrared
radiation below the range mentioned above can provide important information.
Yet apart from this, single- as well as multiple soil property
sensing in laboratories
is possible with remarkable accuracies and is becoming “state of the art”. For on-the-go
sensing in fields,
, this stage of development largely still is a matter of the future.
For
remote sensing
from satellites or from aerial platforms, limitations that
result from atmospheric barriers and from clouds must be considered. Atmospheric
