2.1 Reflection Terminology 
It is owing to Dr. Kriebel, Munich, that the jungle of contradictory and 
in part competing terms and definitions of reflection quantities has been 
cleared up. His paper on "Reflection Terminology for Remote Sensing Appli- 
cations" is copied in these Proceedings. 
According to this paper Kriebel suggests to use the (spectral) reflectance 
factor R(A) as defined in the Technical Report of the Committee TC-2.3 
of the International Commission on Illumination (CIE). This definition 
will also be accepted by the German Standard DIN. 
  
  
The three reflection quantities reflectance ¢ , radiance factor B , 
= 
.and reflectance factor R be once more compared. 
Reflectance 0 : Ratio of the radiation reflected in the hemisphere to the 
incident radiation. 
Radiance factor B : Ratio of the radiation reflected in only one direction 
to the radiation reflected in the same direction by an ideally white 
and uniform diffuser identically irradiated. 
Reflectance factor R : Ratio of the radiation reflected in & finite solid 
angle (cone) to the radiation reflected in the same cone by an ideally 
white and uniform diffuser identically irradiated. 
  
This implies that the reflectance factor R considers the fact that the 
radiation measuring instruments always weight the radiation in a finite 
solid angle. Therefore, this reflection quantity seems to correspond best 
to the illumination and measuring conditions in remote sensing. 
As well as reflectance Q and radiance factor B, the reflectance factor R 
does not umambiguously describe the reflection properties of an object. 
Therefore, & number of specifications must be indicated to make comparisons 
of different measurements more reliable (see also Kriebel's paper in these 
Proceedings). 
It should be specified: 
a) surface: type, species,composition, slope and exposition to sun, 
linear texture and its azimuth difference to sun, period 
length. (the mean distance of the dominant features of a 
surface, as, e.g., the mean distance of tree rows in 
forests), age, growth height, growing status, time of 
season, environmental factors affecting the spectral 
properties, 
b) conditions of position of sun, direct sun or not, degree of cloudiness, 
measurement : wind, wind speed, relation of direct sun to global radi- 
ation, atmospheric turbidity, air temperature and humi- 
dity, mean zenith (nadir) angle and azimuth difference 
of sun to the viewing direction, measuring height, 
c) instrument: field of view, center wavelength and bandwidths of spec- 
tral intervals, integration time of the electronics, 
d) reflection type and size, calibration values, time lapse. 
standard: