Manfred Schroeder 
  
sunphotometer and ground radiometer, already operational for SPOT calibration, will be used here as a 
validation principle. 
3. SPECTRAL REFLECTANCE OF THE TEST SITE 
3.1 Ground reflectance measurements 
Reflectance measurements were made with the Zeiss ... MCS ... Spectrometer [2] in the spectral range 360 ... 950 
nm with a spectral resolution of 3 ... 4 nm; the spectral sampling interval was 0.8 nm. The field of view on the 
ground was about 40 x 40 cm’. As white reference a Ba SO, ... coated panel with calibrated reflectance was 
used. The reflectance measurements were made inside the so called measuring box (Fig .2) of approx. 50m x 
50m. 
  
Fig. 2: Daedalus image of test site from 300m altitude with calibration area and Measuring Box , left: 0.8m x 
0.8m ground pixel size, right: resampled to 18m x 18m ground pixel size. 
During 10:52 and 11:45 GMT on 2 July 1998 250 reflectance measurements were made. The average reflectance 
curve derived from these measurements and its standard deviation is shown in Fig 3. Ground reflectance 
measurements on 29 June 1998 lead to the same results. 
  
280 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B1. Amsterdam 2000. 
  
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