IC as a 
360 ... 950 
^w on the 
ance was 
ox. 50m x 
  
0.8m x 
lectance 
lectance 
  
Manfred Schroeder 
40 , : 
  
1 1 T i 
"mean" —— 
35 L "deviation" ——7— 
20 + 
   
reflectance [%] 
e orae um 
v. ue arret 
+ pe ín 
15 i pe 
t e 
alio s 
10 + 
  
  
  
oO A. i i L i i 
300 400 500 600 700 800 900 1000 
wavelength [nm] 
  
Fig. 3: Ground reflectance (r) and standard deviation measured 2 July 1998. 
3.2 Spatial extrapolation of reflectance by means of airborne multispectral images 
The test site was recorded from 300 m altitude with the 11-channel multispectral scanner Daedalus AADS 1268 
(-Table 1) with a ground pixel size of approx. 0,8 x 0,8 m. The overflight took place at 11:30 GMT on 2 July 
1998; at the same time the ground irradiance was measured 
The full resolution Daedalus image is shown in Fig. 2 (left). To eliminate scan angle effects due to path radiance 
and atmospheric transmittance the radiance values of each pixel along the scan line were relatively adjusted to 
those in the position ofthe measuring box (Fig. 2). 
Dividing the radiances measured in the channels of the Daedalus Scanner by the respective ground irradiances 
give reflectances (r300) as seen from 300 m altitude (Table 1). The scanner and the ground radiometer were 
calibrated with the same standard calibration source. To determine the reflectance for Daedalus-channel 9 (1.57- 
1.78 um the incoming irradiance was computed with the 6S-program (see chapter 5). 
The reflectance values r3o) are compared in table 1 with ground reflectances r of Fig. 3. 
  
  
  
  
  
  
  
  
  
  
  
Channel Aer [pm] Band Edges [um] T390 [79] r [9e] 
1 0.439 0.424 ... 0.450 5.40 7.25 
2 0.494 0.465 ... 0.520 9.46 972 
3 0.564 0.522 ... 0.600 13.51 14.24 
4 0.615 0.594 - 0.634 16.86 17.06 
5 0.660 0.626 ... 0.690 18.38 18.23 
6 0.728 0.692 ... 0.759 20.14 22.47 
7 0.835 0.756 ... 0.906 25.11 25.90 
8 0.960 0.397... 1.022 not used not used 
9 1.677 1.571... 1.780 30.50 30.50 
  
  
  
  
  
  
Table 1: First nine spectral channels of Daedalus AADS 1268 airborne scanner, measured reflectances from 
300m altitude (r39) as well as ground measured reflectances (1). 
Due to atmospheric influences both reflectance measurements are not identical. 
From Table 1 a correction function can be obtained with which the 7309 ... Values for each pixel can be converted 
to equivalent ground reflectances r [7]. ; A 
The corrected average reflectance from all pixels of 0.8 x 0.8 m? in the 400 x 400 m test site and its standard 
deviation can be obtained from the Daedalus image. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 281