SPECTRAL SIGNATURES OF VEGETATION CANOPIES BASED UPON TELE- 
SPECTRORADIOMETER MEASUREMENTS 
S.Jaakkola, P.Saukkola and E.Franssila 
Technical Research Centre of Finland, Espoo, Finland 
T. Introduction 
Studies on the spectral reflectance factors of vegetation canopies 
haven been included in the remote sensing research program at the 
Technical Research Centre of Finland since 1976. The general justi- 
fication for entering these studies is the need to understand better 
the spectral properties of the vegetation being analyzed from multi- 
spectral scanner data. A fairly extensive literature survey covering 
the interaction of the electromagnetic radiation with vegetation 
canopies was completed in 1977. On the basis of this survey, con- 
clusions were made for the accomplishment of the empirical part of 
the study which involves incident hemispherical radiation and re- 
flected radiation recordings from forest stands and, to limited ex- 
tend, from agricultural crops. 
The objectives of the empirical study comprised 1) an analysis of 
the effects of site type, tree species and development stage on the 
spectral signatures of timber stands, 2) the determination of spec- 
tral reflectance factors for those forest strata, and 3) drawing 
conclusions for the planning of forestry remote sensing surveys based 
upon satellite and aircraft scanner data. An overall objective was 
to analyze the spectral properties of forest stand canopies, not 
those tree crowns or leaves alone. That is why the measurements were 
made from a helicopter at 50 to 370 m altitudes.