solar 
ttering 
1, also 
dation 
nse of 
aneous 
INTEREST OF RADIOMETRIC CORRECTIONS 
FOR ENVIRONMENTAL MONITORING 
Xing-Fa Gu 
Gérard Guyot 
INRA 
Station de Bioclimatologie 
B.P.91 
Montfavet, Cedex, France 
ISPRS Commission VII / Working Group 1 
ABSTRACT 
Environmental monitoring needs the analysis and the comparison of multispectral, multitemporal and 
often multisystem data. The only way for performing quantitative analyses is to transform the digital 
counts registered at satellite level, into physical 
units at ground level. The objective of this presentation is to discuss the effects of the different factors 
affecting the signal registered by a satellite: instrument modulation transfer function (MTF) absolute 
calibration of the sensors, non-coincidence of homologous spectral bands, atmospheric effects, target 
directional effects, and to present the recent advances in the correction methods. The discussion is based 
on some examples in visible, near-infrared and thermal infrared, using SPOT-HRV, Landsat-TM and 
NOAA-AVHRR data. 
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