CLASSIFICATION OF HEALTHY AND DISEASED SUGARBEETS 
WITH REGARD TO OBSERVATIONANGLE EFFECTS 
by 
PAUL REICHERT 
University of Freiburg 
Werderring 6 
D 7800 FREIBURG 
RFA 
Airborne MSS-data of a sugarbeet-cultivated area near Frank- 
furt, F.R.G. have been analysed to determine the potential of 
mutlispectral remote sensing and classification for the detection 
various diseases in sugar beets. The analysis has been done in 
the framework of & national research programme and an EEC-Study. 
Spectral signatures of healthy and diseased sugar beets were de- 
termined in situ with a mobile ground station and were calculated 
from the row MSS-data after absolute calibration of the scanner. 
From both platforms, healthy and diseased sugarbeets have shown 
strong differences in their spectral behaviour, which allowed 
for classifícation. However, & strong influence of the observation- 
zenith angle anü the azimuthangle difference (sun- - observation- 
azimuthangle) on the Spectral signatures has been observed. In 
order to enhance the classification results, a model of the 
snbricat reflection behaviour of sugar beets has been developed 
which allowed for the selection of the optimum azimuthangle 
difference (showing minimum observation angle distortions) 
and the determination of a polynomial function to elminate 
observation angle effects. The implementation of this poly- 
nomial function resulted in a coniderable gain in classification 
accuracy. 
The paper should be presented in WG 1:"Methodology for En- 
hancement and thematic Classification of visible and infrared 
Data" of Commission VII 
1035