Full text: Remote sensing for resources development and environmental management (Volume 1)

necessary due to the fact, that the incoming radia 
tion doesn't hit the plant homogenously. The upper 
parts contribute much more to the reflection than 
parts close to the soil. In order to simulate the 
interaction between radiation and plant matter the 
plants have to be analyzed according to their contri 
bution to the reflection. 
- 2. Structure parameters 
The reflection characteristic of plants depends on 
the angular relationships between incoming radiation, 
hidden piece of plant material and measuring device. 
Due to the heterogenous structure of plants the main 
reflection direction may vary. To simulate this it is 
necessary to monitor the geometrical shape of the 
plants and of the whole target surface. 
For wheat the inclination of the leaves and the ear 
as their position at the stem will be determined (cf. 
fig. 4). For the sugar beets the inclination and 
azimuthal orientation of the leaves will be evalu 
ated. Due to the rapid changes in the shape and the 
inclination of the beet leaves depending on the 
turgidity of the plant it is necessary to develop a 
statistical model describing the topographic situa 
tion. 
The structural data will be collected with help of 
stereo pictures. Using these photos, corresponding 
photogrammetric equipment and software the coordi 
nates of object points will be compiled. These then 
serve as basic data for the determination of the 
parameters in question. 
- 3. Meteorologic data 
Most of the climatic values will be measured using 
corresponding meteorologic sensors and devices. The 
I 
Figure 4 : Geometric description of a wheat plant 
- wind direction 
- wind speed 
- global air temperature 
- global air humidity 
- air temperature in the interior of the 
field 
- humidity in the interior of the field 
- light penetration into the field 
- spectral, azimuthal and zenithal distri 
bution of incoming radiation 
Table 2 : Meteorologic parameter 
collected values are listed in tab. 2. 
The last row notes the distribution of the incoming 
radiation. Knowledge about the angular distribution 
of the radiation is important for further compensa 
tion of the influence onto the reflection readings. 
This is of major importance, because very different 
weather conditions are to expect for the campaigns, 
ranging from dry to cloudy or completely covered sky. 
Due to the rapid changes within a partly covered sky, 
the recording device has to monitor the whole sky in 
short time. Because it is impossible to have high 
spectral and angular resolution together with short 
registration cycles only the last two components will 
be considered. These are registrated using a color 
CCD-video camera with 180° field of view, storing the 
signals on a videorecorder. The lost of spectral 
resolution seems acceptable, because the angular 
relations don't change too much with wavelength. 
- 4. Radiometric data 
As measuring device serves the Minarad SA 100/300 
spectro reflectometer. It is a dual channel radiome 
ter covering the spectrum from 0.4 - 2.2 pm with a 
resolution of 0.002 urn (for 0.4 - l.lyjm) and 0.004 
fjm (for 1.1 - 2.2 fjm) respectively. The instrument 
works as a reflectometer. It records incoming and 
reflected target radiation simultaneously. The inco 
ming radiation is integrated over the whole 2irstera- 
dian with help of a diffuser disc integrated into the 
optics or with a diffuse reflecting plate (BaSO^). 
The instrument has the advantage to work in reflecto- 
meter-mode with high spectral resolution in a broad 
part of the electromagnetic spectrum. However, this 
conception results in a relative long measuring time, 
which may range from 5 up to 30 minutes for one 
complete cycle. 
The instrument is mounted on a cherry picker, which 
moves it into the position over the plant targets. 
With help of some modifications at the cherry picker 
the position of the instrument in space is reproduci 
ble, so that for each campaign the measured targets 
will be identically. 
4 DATA PROCESSING 
4.1 Data organization 
The collected data is of very heterogenous structure 
ranging from simple intrinsic values, single measure-
	        
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