is the reflected radiance of the grey reflec-
La
tance standard irradiated exactly as the target.
G
RS C) is the laboratory measured spectral reflectance
factor of the grey reflectance standard.
MEASUREMENT CAMPAIGNS
In the AGRESTE project, the main object of research was
remote sensing of rice crops, poplar afforestation and
natural forest in order to evaluate the potential of
this technique for making inventories of cultivated
areas, yield prediction and disease detection. In this
context many signature measurement campaigns have been
performed some of which will be described in the fol-
lowing.
4.1 A joint experiment? vas made with the I S C (Istituto
Sperimentale Cerialicoltura) in Vercelli; the spectro-
radiometer OPTRONIC 740 has been employed for measur-
ing the spectral reflectance factor of rice which was
grown under greenhouse conditions in ten 40x40 cm? pots.
The Spectroradiometer was placed on a tripod. A ver-
tical view on the rice was possible by looking into a
mirror placed at 45? and 50 cm above the rice pot. A
Philips 1 kw foto flux lamp was used to increase the
incoming irradiance in foggy days during winter time.
The spectral reflectance factor of each rice pot was
determined by using the technique described in section
3.2 and equation (3). This is independent of the spec-
trum of the lamp, of the absorption of sun irradiation
by the glass of the greenhouse, as well as of the mir-
ror reflectivity.
The aim of the experiment was to obtain spectral re-
flectance factors and their evolution related to phe-
nological stages of rice by performing measurements
every ten dayS during the entire growing cicle of rice.
The scheduled periodicity of measurements could not
be maintained. Therefore the original goal was not
completely met. The results of the experiment were
usefull, however, in that the temporal spectral reflec-
tance factor evolution unespectedly revealed that two
Classes of rice had been grown. This was discovered
from a different exposure of pots to direct sun irra-
diation resulting in a significant difference in rice
production.
